Table of Contents
TECHNICAL CONTENT ...................................................................................... 1
Project Identification and Significance........................................................................................................1
Objectives and Goals .....................................................................................................................................2
Research and Investigations .........................................................................................................................3
Power Distribution......................................................................................................................................3
AC vs. DC ..............................................................................................................................................4
Power Conversion ..................................................................................................................................5
Cables and Outlets .................................................................................................................................7
AC Line Switching .....................................................................................................................................8
AC Switch Block ...................................................................................................................................9
Power MOSFET ....................................................................................................................................9
Mechanical Switch ............................................................................................................................... 10
Remote Control Power ............................................................................................................................. 12
Microcontrollers ....................................................................................................................................... 16
Remote Control Microcontroller .......................................................................................................... 18
Input/Output Programming Controls .............................................................................................. 18
Wall Unit Microcontroller ................................................................................................................... 21
Input/Output Programming Controls .............................................................................................. 21
End-User Programming ....................................................................................................................... 24
Radio Frequency Communication ............................................................................................................ 25
Antenna ................................................................................................................................................ 27
Receiver ............................................................................................................................................... 28
Decoder ................................................................................................................................................ 29
Transmitter ........................................................................................................................................... 30
Encoder ................................................................................................................................................ 31
Packet Transmission ............................................................................................................................ 32
Packet Transmission Protocol .............................................................................................................. 33
Transceiver .......................................................................................................................................... 34
Wall Dimmer ............................................................................................................................................ 35
Liquid Crystal Display (LCD) .................................................................................................................. 36
Speech Recognition .................................................................................................................................. 38
Personnel and Bibliography ....................................................................................................................... 41
John Bambace ........................................................................................................................................... 41
Eric Marshall ............................................................................................................................................ 41
Mike Segarra ............................................................................................................................................ 42
Drew Yenzer ............................................................................................................................................. 42
Milestone Chart ........................................................................................................................................... 43
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Technical Content
Project Identification and Significance
The purpose of the design project is to construct a wireless home lighting control system.
This project varies from other home lighting control systems in that it will work
wirelessly. Most commercial systems currently require that all wall switch panels be
physically wired during installation to one or more master control panels. As such, these
systems are usually installed during the construction of new homes. With a wireless
system, installation can occur in existing homes without extraneous rewiring. To clarify,
this system is not limited to just lighting, but can operate any AC device connected to a
wall switch.
One of the advantages of wireless devices over those driven through wires is simple
convenience. Wireless devices are portable and therefore are not limited by the lengths
of the wires involved. This means that an individual could turn lights on and off without
leaving the comfort of their living room love seat. Besides the obvious issue of comfort,
an individual could manage the lights in their house without having to visit each room
(due to a status check for each light on the remote that will be discussed in the next
paragraph). By governing the settings of each light in the household, an individual would
have more control over one aspect of their power bill and would limit wasteful lighting
activity.
Instead of a master control panel, the lighting control system will have a remote control
that can be taken anywhere throughout the residence and still operate the lights of any
room. The remote can be programmable so that any one button can toggle a single room,
a series of lights, or the entire home. The user will also be able to view the status of all
the lights in the home with the push of a button on the remote’s LCD screen. If the
project is developed in its entirety, then the remote will have a wall mount that will
recharge it without disabling the capability of the remote (therefore duplicating the role
of a master control panel).
Besides the remote access to the light, a multitude features independent of the remote
control shall be built into the wall unit. The project will have dimming capability so that
the lights can be dimmed through the wall interface or the remote control. In addition to
dimming, the wall unit will have speech recognition, which is by far one of the most
overlooked control mechanisms for modern electronics. The advantages of speech
control include ease of use, and the aforementioned advantage of being a unique
capability on the market. Very few electronics nowadays implement speech control,
which will give the finished design an edge on the modern market. Among the
commands recognized will be an ON/OFF toggle, a dim vs. brighten option, and, if the
design team is overly ambitious, the control of other rooms in the home; thereby
bypassing the need to have the remote on hand.
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Objectives and Goals
For the design to be successful there are a variety of objectives and goals to be achieved.
This project needs to be:




Cost effective
Small
Easy to incorporate
Capable of wireless operation
There are products available on the market that accomplishes many of the features that
are to be incorporated within the wireless light control system. Those products are often
very expensive. If the project could be built with comparable features, and at a lower
cost it would be more attractive to consumers. Thus proposed project will have to cost
substantially less to be successful.
The incorporated device must be small enough to be easily managed by end users. The
remote unit should not be too large, heavy, or bulky because this would cause an overall
disappointing experience. The wall unit cannot be too large either. The replacement
switch is to fit in the preexisting wall unit. This means the components chosen and
design of the entire wall switch unit is extremely limited to the real estate available.
The installation of the design should be easy for anyone with knowledge in home electric
wiring. The design will have the input and output AC line cables readily available and
labeled. The existing power lines coming in will be connected to the properly labeled
switch wires and the switch output line will be connected to the wires running to the
light. The user would then authenticate the radio address that will allow the remote to
properly communicate with the wall. The explained is much easier than other methods
currently employed on the market that require rewiring of the entire household, or only
allowing the wireless to work if the wall switch is on.
The main purpose of the proposed design project allows for wireless control of the
lighting system existing in a domicile. The remote unit will incorporate an ad-hoc
wireless communication system. The proposed system allows communication between
the remote and any light residing within the house. This type of light management would
allow a home owner not only to save power but also adds an exemplary amount of
convenience when operating the illumination devices.
When all the stated objectives and goals are incorporated into the final design this project
will provide an easily installed, power saving, convenient, and low cost wireless light
control for the entire residence.
2
Research and Investigations
Power Distribution
The power distribution for this senior design project is most efficiently expressed by a
generic block diagram. In this block diagram presented below, the AC line powers the
light when the AC switch is closed. Three possible choices for this AC switch include an
AC Switch Block, a power MOSFET, or a mechanical switch powered by a servomotor
(see AC Line Switching section). A DC signal is sent to the wall switch (here, a push
button) that will then pulse a 5 V signal to the microcontroller when the switch is pushed
on. Whenever the microcontroller is pulsed, it will toggle the status of the AC switch,
and the light will turn off if it is on or on if it is off. DC voltage will also power the AC
switch, the microcontroller, and the RF transceiver. This transceiver will receive the
signal from the wireless remote and pulse the microcontroller as well when the remote
sends an off or on signal (see Transceiver section for more information).
AC
Line
AC Switch
Light
AC / DC
Microcontroller
Converter
Wall Switch
(Push Button)
RF
Antenna
Transceiver
Figure 1: Proposed Block Diagram
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AC vs. DC
There are two types of power, AC and DC. AC, or alternating current, is when electricity
is passed in a form where the magnitude and direction of the current vary by a period of
time. DC, or direct current, involves a constant flow of charge from high to low
potential. Both forms have their advantages and disadvantages. For instance, DC is
more practical for those situations requiring lower voltages, and can be directly produced
by batteries or solar cells. AC, on the other hand, is convenient for higher voltage
applications, but is more difficult to generate.
Instantaneous power is determined by the equation P(t) = I(t) * V(t). For DC power,
power is simply current times voltage; through a resistor this becomes I^2 * R or V^2 / R.
In AC power, the total power is determined by a complex formula S = P + j*Q, where S
is the apparent or complex power, P is the real power, and Q is the reactive power.
Apparent power is measured in volt-amperes (VA) and the reactive power is in units
called volt-amperes-reactive (VAR). Usually this relationship is defined by a “power
triangle.”
Figure 2: Power Triangle (Courtesy of Wikipedia)
By using the Pythagorean Theory, (apparent power)^2 = (real power)^2 + (reactive
power) ^2, or S^2 = P^2 + Q^2. This apparent AC power was chosen to be more suitable
for the light in this design than DC, which is further explained through the subsequent
discussion on power loss.
Appliances require a certain amount of power, and if the voltage is cut by n, n*current
will be needed (by the equation P = I * V). However, in a direct-current application, lost
power is defined by the equation I^2 * R. This means that the power loss will not by a
ratio of n, but n^2. To compensate for this high power loss, large wires would have to be
implemented, which is an expensive solution.
For this reason (and the fact that AC power can be transported long distances through the
exercise of transformers), households are strictly powered by alternating current. In the
United States (as well as Canada and Mexico), the electrical standards for AC lines are
100-127 V (usually 120 V) and 60 Hz. In Europe, Africa, and Asia, the standards are
much different: 220-240 V and 50 Hz.
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Power Conversion
There are four possible ways to convert voltages: AC to DC, DC to AC, DC to DC, and
AC to AC. AC to DC, the relevant scenario for this project, will be explored in the
following paragraphs. To briefly summarize the other cases: DC to AC is known as
inversion, and is usually an expensive and impractical process. DC to DC is considered a
kind of voltage regulation and will be vital in the conversion of AC to DC. Finally, AC
to AC is a complicated process and usually requires converting AC to DC and then
inverting that DC voltage back to AC.
Although the light bulb will require AC power to operate, the microcontroller, the push
button, the AC switch, the microcontroller, and the RF transceiver require DC (see
diagram). Instead of powering these parts of the circuit with some separate DC voltage
source, it would be easier and more practical to use an AC to DC converter.
To successfully convert AC to DC, certain steps must be followed. The flowchart below
details an efficient method of reaching a DC output voltage from a sinusoidal input.
AC INPUT
Full-Wave
Rectifier (with
Transformer)
Voltage
Filter
Regulator
DC
OUTPUT
Figure 3: Block Diagram for AC to DC Conversion
The first step, rectification, changes all negative input to positive (or all positive input to
negative, but this case will be ignored). For a sinusoidal AC signal, the first half of the
period will remain the same. However, the second half of the period (the negative
portion) will become positive. A pictorial view of this process, along with the bridgerectifier responsible for the conversion, is presented below:
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Figure 4: Full-Wave Rectification with Bridge Rectifier (Courtesy of Wikipedia)
The bridge-rectifier above is one circuit that produces this full-wave rectification; halfwave rectification has a zero-volt output for the negative half of the alternating current
input. Another circuit could be designed if the transformer is center-tapped (possessing a
wired output halfway through its windings):
Figure 5: Full-Wave Rectification with Center-Tapped Rectifier (Courtesy of Wikipedia)
If the transformer used is center-tapped, this circuit would be preferred. Only two diodes
are needed, compared to the four required for the first bridge rectifier. The transformer
increases or decreases the AC voltage to a desired AC level, and then is rectified by the
circuit. This unregulated voltage will be similar to DC after being sent through a filter
circuit.
Finally, a voltage regulator will convert this new DC voltage to another DC level higher
or lower than before. The output will be compared with a certain reference value and
ensure this proper output is reached. Similar to the concept of feedback, this voltage
regulator is also known as a smoothing circuit. The efficiency of the rectification can be
found with the following ratio:
, where the DC is the output power and the AC is
considered the input power. Without a voltage regulator, a full-wave rectifier typically
has 81% efficiency, or
efficiency, or
. Half-wave rectifiers, on the other hand, have 40.5%
.
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Cables and Outlets
The preceding discussion on cables and outlets is a vital one to the completion of this
project. During testing and design, an AC voltage source must be manufactured by the
team to follow the generic design circuit. Proper understanding of wires, cables, and
outlets is mandatory for this to be a successful task.
A cable is considered as two or more wires held together by a sheath. There are several
types of cable, including AC, BX, MC, MI, UF, and NEC type NM-B. Type AC cable is
characteristic for an interlocking metallic sheath (usually made from steel or aluminum).
BX is similar to AC expect its prime implementation was during the Second World War.
MC cabling is used universally for wet and dry applications because of its flameretardant property. MI (Mineral Insulated Copper Clad) cables are also resistant to fire,
but use magnesium oxide as insulators. UF (Underground Feeder), a nonmetallic cable,
is used underground and in many locations because of its resistance to heat, light, and
wetness. Finally, NEC type NM-B is the most common nonmetallic cable and is also
known by its brand name, Romex. This plastic-insulated wire is most practically
implemented in protected areas, which accounts for its popularity in the wiring of new
homes.
In the United States, two-wire cabling actually contains three wires: live, neutral, and
ground. A three-wire cable is composed of the same three wires as before (live, neutral,
and ground) with the addition of a fourth wire: a traveler or switch wire. Usually, a white
wire is considered “neutral,” a red wire (or a white wire taped with black) is known as the
“traveler” or “switch” wire, a black wire is the “hot” or “live” feed, and a green wire is
the “ground” wire.
In the United States, electrical wiring must follow standards listed in the National
Electrical Code (established in 1885). This code is updated every three years and was
just updated in 2005. One of the most recent requirements governed by the NEC is that
new household outlets be grounded and polarized. Therefore, a typical AC outlet can be
defined with the following pins:
Figure 6: Typical Outlet (Courtesy of Wikipedia)
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The ground is common to both the “hot” and “neutral” slots and the “hot” pin on the right
is noticeably smaller than the “neutral” one. For those devices whose cabling is
ungrounded (having only two plugs, not three), the difference in size between the
“neutral” and “hot” outlet pins ensures the “neutral” will serve correctly as the ground
connection.
Lastly, the National Electric Code also has provisions for where outlets can be located in
a household, allocating a certain number of sockets per unit floor area. A ground fault
circuit interrupter is mandatory for almost all outlets, especially those in kitchens,
bathrooms, garages, and basements. These GFCIs can shut off the outlet immediately if
there is an electrical hazard. Similar to other outlets, the receptacle for a GFCI only
differs by its two buttons in the middle of the unit.
Figure 7: Typical GFCI (Pending Permission Request)
The two buttons on a GFCI are “reset” and “test.” By pressing “test,” an imbalance is
created in the line, and the device is tripped. This simulates an overload in the line and
ensures the device is working correctly (by making a snapping sound). After pushing
“test,” the “reset” button must be pushed for the GFCI to return to normal operation.
AC Line Switching
There are three options to switch the AC line from open to closed, which will in turn
allow the light to turn off and on, respectively (see Proposed Block Diagram). The first
option considered will be an AC switch block.
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AC Switch Block
Figure 8: AC Switch Block (Pending Permission Request)
This first choice for the switching on the AC line is sold commercially. Here a small DC
signal opens and closes an AC line, which is connected to the two AC terminals on the
right side of the block. By sending a 5-volt DC signal through the D0 input and
grounding the 0 V input, the device will close the AC line and turn whatever AC
appliance on. If a 0 V signal is sent instead, the AC switch block will open the AC line
and the AC appliance (in this case, the light) will be off.
This switch can only handle up to 16 amps of current, resulting in 1920 watts of power
for a 120-V household outlet (P = I*V). Also, the “live” or “hot” wire of the AC power
cord should be the one connected to the AC terminals of the AC switch block (see earlier
section on Cables and Outlets).
Power MOSFET
Another option for the switching of the AC Line is a power MOSFET, or Metal Oxide
Semiconductor Field-Effect Transistor. A typical MOSFET is a voltage-controlled
device used on large-power applications, but a power MOSFET forms its distinction from
other transistors by being efficient at low voltages. This device is considered the most
universal low-voltage (less than 200 V) switch.
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Figure 9: Cross Section of a Power MOSFET (Courtesy of Wikipedia)
Figure 10: Cross Section of a Lateral MOSFET (Courtesy of Wikipedia)
In a lateral MOSFET, when the voltage across the gate-source is below the threshold
voltage (usually .7 volts), the MOSFET is off. When this VGS is greater than .7 volts, the
MOSFET is on and conducts the current. This continues until the MOSFET is in
saturation. When the MOSFET is on, it acts as closed switch and will close the AC line
in turn, acting as an appropriate switch.
Unlike a typical lateral MOSFET, the power MOSFET has a vertical structure, which
means the current and breakdown voltage ratings are not dependent on the width and
length of the channel (see cross section of the power MOSFET above.) The current
rating is still dependent on the channel (specifically, the width), but the voltage rating is a
function of the doping and thickness of the N epitaxial layer. By increasing the doping
level and decreasing the thickness of the layer, the resistance between drain and source
(when the transistor is on) will decrease significantly, therefore minimizing the losses
during operation. Oppositely, with a lower doping and thicker epitaxial layer, the
breakdown voltage of the MOSFET will be higher.
Mechanical Switch
The last method for switching the AC line is not nearly as practical as the other two
solutions. By attaching a servomotor (an electrometrical device with a motor shaft) to a
regular light switch, a voltage could be used to physically close or open the switch, and
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therefore the AC line. To fully understand the implementation of such a toggle, a more
extensive look at mechanical switches follows here. (Note: this mechanical switch
should not be confused with the push button “wall switch” responsible for pulsing the
microcontroller.)
By definition, a switch either terminates or completes an electrical circuit. The power
described earlier can not flow through any appliance (or a light, as in this case) when a
switch is closed, because the circuit will be open and the current can not conduct. There
are several different kinds of switches, including wall switches, aforementioned circuit
breakers, push-button switches, and mercury switches.
In a switch, two contacts made of metal can either touch to complete the circuit or break
and open the circuit. The actuator is the moving part inside the switch that will either
connect or disconnect these two contacts. A set of contacts in a switch is referred to as a
‘pole,’ where as a ‘throw’ is one of the positions a switch can assume.
A “single pole, single throw” (SPST) switch is known as a two-way. This is the most
common configuration and is represented by the symbol:
. Although
the United States prefers to call this a two-way switch, Britain refers to it as a one-way.
Here there is only one set of contacts and one position.
A “single pole, double throw” (SPDT) switch is referred to as a three-way switch. Its
symbol is:
. This switch still has one set of contacts, but two
positions it can assume. Unsurprisingly, Britain refers to this as a two-way. Three-way
switches are used in situations where the same light can be controlled from two separate
locations, like two ends of a hallway. A SPDT switch is unlike the SPST, which allows
for control of a light from only one location.
To design a SPDT switch, two three-way switches are connected in series as shown in the
following picture:
Figure 11: Configuration of a Three-Way Switch (Pending Permission Request)
In the circuit above, both switches are in the “OFF” position, so the light is also off.
Because the two switches share a common terminal, the light will turn on when one light
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is flipped to the “ON” position (a complete path will exist through both switches).
However, if both switches are “ON,” there will not be a complete path through a common
terminal and the light will turn off.
In closing, a four-way switch can control a light from three or more locations (a five-way
can control from four or more locations, etc). These four-way switches are related to two
less common switch configurations known as “double pole, single throw” (DPST) and
“double pole, double throw” (DPDT). There are no discrepancies between the British
equivalents of these terminologies.
This project seeks to replicate the behavior of a three-way switch. The design team
wishes to turn on a light form at least two separate locations, with the remote and without
(by physically flipping the switch). If both the switch is flipped to the “ON” position and
the remote toggles the light to be “ON,” the light should turn off, mirroring what happens
with two three-way switches in the “ON” position.
Remote Control Power
The power source for the remote control unit must be small, portable, and supply direct
current. The only device that fits the bill is a battery. The two types that exist are
disposable and rechargeable. Disposable batteries are the kind that are bought at almost
any store (AA’s for instance) and are generally used for applications with either low
current drain or intermittent usage. Rechargeable batteries are just that; they can be
recharged with the application of an external current, so power drain is not as large a
factor than with disposable batteries. When referencing the capacity of a battery to store
charge, Ampere-hours is used. If a battery can provide 1 Amp for an hour then it is rated
as 1 A*h. When discussing rechargeable batteries the term ‘memory effect’ is often
employed. This is an effect that occurs when a battery is repeatedly overcharged, then on
subsequent discharges the voltage across the battery decreases much faster giving the
illusion it is losing its charge faster.
Alkaline batteries (Figure 12) are the most common disposable that are found in stores.
They frequently come in standard sizes of AAA, AA, C, D, and 9 Volt. All of these sizes
are cylindrical 1.5 Volt batteries except for the rectangular 9 Volts. The difference in the
sizes is the amount of charge it carries with AAA being the least at 1250 mA*h and D
being the greatest at 20500 mA*h. Multiple batteries of the same size would be needed
to obtain the necessary voltage used by the remote control.
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Figure 12: Two Duracell AAA Batteries (Courtesy of Wikipedia)
The only other disposable worth considering is the Zinc-Carbon battery (Figure 13). The
main benefit of this battery is that it is the least expensive. However in every other
regard it is inferior to alkaline batteries. It initially produces about 1.5 Volts, but as time
goes on, regardless of use, this potential steadily drops. Furthermore the outer casing of
these batteries is part of the chemical reaction (it is the zinc anode), so as the battery is
depleted the casing thins and in some instances can leak the contents, damaging the
attached electronic circuits.
Figure 13: Zinc-Carbon Batteries (Courtesy of Wikipedia)
The first of many rechargeable batteries to be considered is Lithium Ion (Figure 14).
Lithium Ion batteries have one of the best energy to weight ratios, so they can be made
very small and light compared to other rechargeables. They do not suffer from memory
effect and have a low self discharge rate of approximately 5% per month. Also their
lifespan remains relatively unaffected if they are kept charging after they have been fully
charged. Other rechargeables usually degrade in those circumstances. A unique
drawback of the Lithium Ion battery is its lifespan is dependent upon not only the number
of charge/discharge cycles, but its age from time of manufacture. At 100% charge level a
typical Lithium Ion battery will lose approximately 20% capacity per year even when it is
being unused. Depleting the battery to 0% through use, called a deep discharge cycle,
will lower its charge capacity. Approximately 100 deep discharge cycles leave the
battery with about 75% to 85% capacity. Lastly, Lithium Ion batteries are more
expensive than and not as durable as other rechargeables. They can be extremely
dangerous if mistreated because lithium is highly volatile.
13
Figure 14: Prismatic Li-Ion Cells (Courtesy of Wikipedia)
The main difference between Lithium Ion and Lithium Ion Polymer batteries is the
former requires a rigid metal case, which presses the internal components together,
whereas the polymer batteries’ internal components are laminated together and do not
require rigid casing. Therefore Lithium Polymer batteries can be lighter and specifically
molded to fit the device it will power. This also gives them over 20% higher energy
density than that of Lithium Ion batteries. The charge/discharge cycle degradation rate is
also higher than that of Lithium Ion. Recently manufacturers have declared upwards of
500 charge/discharge cycles before the battery drops below 80% capacity.
Figure 15: NASA Prototype of a Lithium-Ion Polymer Battery (Courtesy of Wikipedia)
Lead Acid batteries (Figure 16) are the most common rechargeable used today. They
have one of the lowest energy to weight ratios but their power to weight ratio can be high.
Lead-Acids are some of the cheapest rechargeable batteries and have high surge currents.
It is for this quality that they are often used to power starting motors (car batteries are
lead-acid). Lead-Acids come in a couple different flavors: Gel and Absorbed Glass Mat.
These are used for different situations, such as shock absorbance, but operate on the same
principles. Lead Acid batteries are simply too large and heavy to be considered as a
viable power source for the remote controlling unit.
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Figure 16: Lead Acid Battery (Courtesy of Wikipedia)
Nickel-Cadmium batteries (Figure 17) are mostly used to power portable electronics and
toys. Sometimes they are even used as replacements for alkaline batteries as they are
available in many of the same sizes. Their nominal cell potential is 1.2 Volts, so they are
not always a viable replacement, but unlike most batteries they keep a near constant
voltage throughout their service (most batteries degrade in potential as their charge
decreases). They have a long service life and are difficult to damage, but are more
expensive than alkaline batteries. Self discharge on Nickel-Cadmium batteries is high at
20% per month.
Figure 17: (From top to bottom): "Gumstick," AA, and AAA Nickel-Cadmium Rechargeable
Batteries (Courtesy of Wikipedia)
Nickel Metal Hydride battery (NiMH, Figure 18) is similar to Nickel-Cadmium except
the environmentally hazardous cadmium is replaced by a hydride, so this battery is less
detrimental to the environment. NiMH batteries have greater charge capacity than
Nickel-Cadmium (2-3 times more) and the memory effect is less significant, but
volumetric energy density is lower and self discharge is higher at 30% per month. NiMH
batteries do not have the low internal resistance of Nickel-Cadmium, so surge currents
are not high, but they perform better with moderate drain devices, such as the remote
control unit.
15
Figure 18: NiMH Rechargeable Batteries (Courtesy of Wikipedia)
Microcontrollers
There are a number of microcontroller components that must be taken into consideration
when viewing different units. These necessary types and values for each part will vary
from one controller to another, but the general information remains constant throughout.
The ‘generic’ microcontroller information that needs to be researched before purchase is
as follows:
 General input/output pins available
 Type of communication between components
 Development environments available
 Onboard memory available
 Power needed for operation
 Cost of controller and development kits
The number of input and output pins is an essential aspect of the microcontroller. These
pins are what allow the controller unit to communicate with other devices that may be
connected. Thus, there must be an adequate number of pins that will be reserved for
various functions. If there are an insufficient number of pins then the system would not
have proper communication between devices and would never properly function. One
would also want to avoid purchasing a controller with too many in/out pins. The reason
is that more pins generally mean a larger controller and a slight increase of price. To
ensure that the proper amount of in/out pins are selected for the controller, it would be
advised to tally up how many pins are required for each device to be interfaced with the
controller. Microcontrollers come equipped with a wide range of general input/output
pins available. There are models with as few as four and far exceeding forty pins. This
makes the controllers able to handle a wide range of applications.
The type of communication the microcontroller uses over the input and output pins is also
an important issue to be dealt with. The communication between components must be
synchronized in some way to make sure that the data is properly passed. If the
components are not coordinated with each other, data may be lost due to false highs and
lows in the voltages, or the signal may not be stable for the proper amount prior to the
clock change to properly read the data. There are a few methods easily incorporated to
16
make sure the components are in step with one another. One method is using a general
clock line that would stem from the microcontroller and connect to the various
components. This would ensure that all components are running in harmony with each
other. The use of this method would cause an extra bus line on the developed circuit
board. Another method is called asynchronous communication and would be
accomplished by the use of a serial communication line. Communication done in this
fashion requires no clock line for synchronization. This would mean that when the
components want to talk to one another there would be a “handshake” between them.
This handshake allows the different components to send the data between them at the
same speeds, and in step with one another. The downside to this is the increased
overhead in the information passed between components. To do this the microcontroller
and the connected device would need to have input/output pins that supported a serial
communication. Controllers currently available can support one or both of the
communication types mentioned above making them suited for the connection of many
different devices.
The environments available for one to program the microcontroller is another aspect one
would look into when purchasing a suitable unit. Depending on the brand and model
there are different programming languages that one could use. Most controllers allow a
person to design the code an assembly language that is native to the brand to program the
unit. Some will allow a user to use a high level language such as C or C++ to develop
their chip. While coding in C and other high level languages is generally machine
independent assembly languages can differ from chip to chip. For different brands there
are different registers available and different ways to write and store data. When
considering which environment to choose one should consider what languages they are
more comfortable with. Also if choosing an assembly environment one should review
the structure of the language before programming. Choosing a more familiar language
will reduce development time and reduce the amount of programming errors that may
occur.
Onboard memory is another key factor when selecting a microcontroller. This memory is
used to store not only any data that will be sent to and retrieved from the controller, but
also the programming that allows your controller to work properly. There are many
different values of memory available on controllers that make it easy to select a proper
amount. Depending on the complexity and number of functions to be incorporated within
the unit the more memory one would need available. In many cases the memory
available for the main programming and input/output data is separated. This allows the
programmer to make sure when data is being written to the controller no part of the
controllers programming is being deleted or overwritten. Different types of memory
available on chips such as random access memory (RAM), read only memory (ROM),
and FLASH memory. The different types would serve different purposes. RAM is
volatile memory so if there is power disruption all data stored would be lost. This is not a
memory that one would use for programming but rather use for temporary data that is
sent and received from the controller. The FLASH and ROM is a non-volatile memory
and would be ideal for placing the controller’s main programming on. This is because
even if there is no power the information stored will remain keeping the unit functional.
17
If the main software running the controller was lost the unit would be rendered
completely inoperative. Of course selecting the exact amount of memory needed would
be ideal the amount is not easily calculated. If unsure of the amount needed it would be
better to use a non-conservative estimate.
The voltage levels required by the microcontroller to operate are very important for many
projects. In nearly every project power consumption is a factor to consider. If the power
consumption of the chip is large it will cost more to operate, or drain battery power often.
In order to keep cost of electricity down and extend the life of batteries a microcontroller
that consumes very little power would be ideal in nearly all cases. The operating voltage
of a chip can be as low as 1.8 volts (for ultra-low power devices) to approximately 8
volts. Other power saving features included on many controller units is use of standby
and hibernate modes. Standby modes allow the chip to suspend most operations and run
at very low power levels. The unit uses an interrupt to return to its active mode, which is
initiated by some type of input caused from by an end user or connected device.
Hibernate mode allows the chip to store all data currently being used and completely turn
the chip off. Thus when the controller is put into hibernate mode all temporary data is
stored on non-volatile memory and the chip is turned off to stop the usage of power. The
next time the unit is powered on all of the saved information is reloaded into its proper
location of RAM and the controller is returned into the operational mode. Nearly all
controllers available support many levels of standby modes and a hibernate mode. This
allows developers to decrease the amount of power consumption as much as possible.
To keep the final design cost of a project down the price per microcontroller and for the
development kits need to be researched. Many controllers are available at a fairly low
cost ranging from approximately three to fifteen dollars. The development kits however
can run substantially higher in price. There are a few factors that influence the price of
development kits, the brand, family, and features. These packages can cost a person or
business as little as twenty dollars and can exceed two hundred dollars. Some of the
features that may be included in a development kit include support for high level
programming, USB or serial port interfacing, simulation tools for the controller,
simulation tools for interfacing controller with other devices, and development boards.
Often the more tools that one could purchase in the kit the easier it is to program the
microcontroller. This is due the added support and testing methods.
Remote Control Microcontroller
Input/Output Programming Controls
The main module that will be managing the remote control unit is the microcontroller.
This unit will be responsible for controlling a variety of devices as follows:
 RF Transceiver
 LCD with LED Backlight
 End User Input Commands
18
When choosing the proper controller for this part of the design project the following
controller specifications where considered:
 General Input/Output Pins
o Supported Communication
 Development Kits
o Features and Environments
 Onboard Memory
 Power Consumption
The microcontroller will be responsible for setting the RF transceiver into send/receive
mode, switching the unit on and off, and communicating packet data between them.
Most of the RF transceivers viewed have two general in/out pins, but if the transceivers
are bought in units of a receiver, and transmitter there will be four pins required on the
controller unit. These pins will be used to transport information to and from the
controller and transceiver. The microcontroller will use the design teams developed
software to organize and read the data included into the packets that are being transmitted
wirelessly. When not in use the microcontroller will be switching the RF unit on/off or
into sleep modes to preserve power.
To display text an LCD with a LED backlight will be incorporated. These units will be in
part controlled by the microcontroller. Many of the displays use ten control pins that will
be connected to the controller. Two of the pins will set the modes the LCD is currently
in. The microcontroller will then send a high or low signal over the other eight pins that
correspond to specific ASCII symbols to be displayed. This will be controlled by the
controller’s software, and will be done by loading each bit of the ACCII character onto
the proper output pin. The controller will also have to set the LCD into a
"standby/hibernate" mode when not in use. This will help prolong battery life by
lowering power consumption.
The user inputs from the remote unit will also have to be run through the microcontroller.
These inputs will be translated by the microcontroller to provide a variety of functions
that must be programmed into the controller. A few examples of the routines would be to
toggle a light between on and off, check the status of the lights and set a particular switch
to a button. The number of pins required to accomplish this greatly depends on how
many rooms the system will be allowed to handle, and how many lights are available per
room. If the system is to be robust enough to handle nearly all clients there will need to
be approximately eight rooms with four lights per room. This would allow the system to
compensate for thirty two different light switches. For the controller to accept this
amount of rooms and lights there would need to be eleven input/output pins. For the user
to check the status of the lights and to set the switches to buttons there would be an
additional two pins used. Thus there would be a preliminary total of thirteen user input
pins. This value may vary depending on the specs of the final product.
The remote control unit needs a microcontroller that would be able to support
approximately twenty seven general input/output pins. The communication over these
19
pins may need to be serial or clocked depending on the connected devices. The
specifications noted are easily achieved with available products.
Using a development kit that enables extensive virtual testing would allow for an easier
implementation of the remote control. It would also benefit the design team to select a
kit that allows for high level programming, and supports USB interface.
The amount of memory that will be needed for the remote control is not yet known. This
is a hard value to quantize of the information already known. What is known are the
types of memory that should be available and approximate complexity of the controller’s
software. The remote unit should include both ROM or FLASH and RAM. The ROM or
FLASH will be used for the main software and other information such as a table of
addresses for each light. The RAM will be used to send data to the other components
such as the LCD and transceiver. There should also be substantially more ROM or
FLASH when compared to the amount of RAM.
The amount of power needed to run the microcontroller of the remote control is a very
important aspect to consider for this project. This is because the remote unit will be
battery powered. Thus a low power unit is necessary to prolong battery life. The models
of controllers that operate at 1.8 volts would be a first choice in controllers. An ideal
controller for this project would also allow for both standby and a hibernate modes.
For the project at hand the ideal specifications for the microcontroller would be:
 At least 27 general input/output pins
o Supporting Asynchronous communication (Serial)
o Available Clock Line
 Familiar Development Environment such as the C programming
language
o Virtual development and testing
 Combination of Memory types
o FLASH or ROM for program
o RAM for temporary data
 Low power consumption
o 1.8 volts to power
 Low cost for chip and development tools
A basic diagram of the microcontroller and component interface is as follows:
20
LCD & LED
Photo Diode
10
MicroController
4
13
End User Input
ROM/FLASH
RAM
RF Transceiver
ALU
PC
Voltage Source
Figure 19: Remote Control Microcontroller Interface
Wall Unit Microcontroller
Input/Output Programming Controls
The main module that will be controlling the wall switch unit is the microcontroller. This
unit will be responsible for controlling the following devices:
 RF Transceiver
 Power Switch
 Dimmer
 End User Inputs
When choosing the proper controller for this part of the design project the following
controller specifications where considered:
 General Input/Output Pins
o Supported Communication
 Development Kits
o Features and Environments
 Onboard Memory
 Power Consumption
21
The RF communication for the wall switch will work in much the same way the remote
control will manage the device. The packet information will be organized and analyzed
in the same fashion. The main difference is that the use of the hibernate function will not
be employed. The wall switch may receive wireless data without any prior warning so
the RF transceiver will need to stay in either the operational or standby modes.
Two turn the light on and off a switch will need to be incorporated onto the AC line.
Many of the wireless light controls on the market require the wall switch to be on for the
remote control to work. To circumvent the problem the microcontroller will control the
light from the switch and the allowing independent toggling of the light between the wall
switch and remote control unit. There are different ways to do this, one method is to
have a physical switch that will break and connect the AC power line when the light
status is to be switched. In order to turn on or off the light the physical switch would
receive a signal from the microcontroller to change its status. The positive side to this is
that there will be no power loss when the light is not on. The downsides include the
possible malfunction of the mechanical switch. Another possible method is to use a
power metal oxide field effect transistor (MOSFET) to control the switch. This method
would also be controlled by the microcontroller. When the MOSFET is to be on an
output voltage from the controller would be sent to the transistor. By eliminating this
voltage the MOSFET would not allow the AC power to flow through to the light. This
allows the switch to be digitally controlled and lowers the possibility for mechanical
failure. On the other hand there is some power loss when the transistor is off. For this
project the power MOSFET seems to be the best choice. This device requires only one
control line from the microcontroller and is smaller in size than a physical switch.
A dimmer for the lights would also be controlled by the microcontroller. This would
require approximately one input/output pin. When a dimming level is selected by the end
user the microcontroller would have to compute the proper level and set a triode for
alternating current (TRAIC) to fire at the appropriate level. If the dimming is set to half
power the controller needs to set the TRIAC to fire when the AC voltage is at half power.
This is possible because the voltage and frequency is known so the controller will have to
have a preset function to find the proper levels.
The microcontroller for the wall switch will also have to take inputs from the user and
process that input to manage the device. There will be two main inputs the controller will
have to analyze one from the wall switch, and one from the dimmer. Each of these will
require one input/output pin and have preset functions written into the main program to
properly mange the device. If the end user uses the wall switch to turn the light on or off
the microcontroller will have to take this input and then analyze the current status of the
light. When the status if found it will be changed by the controller. When the dimming
level is set the controller needs to find the level dimming is required and send the proper
information to the TRIAC which will fire when the voltage level of the AC line is at the
corresponding level.
A preliminary count of input and output pins results in approximately eight pins
necessary for the wall switch microcontroller. This controller like the remotes will need
22
to support both serial communication and clocked. Connected devices such as the power
MOSFET may not need to be clocked or use serial communication. Only further
investigation will verify this. Again there are units available that meet the required
specifications.
Using a microcontroller of the same brand and family as the one utilized in the remote
control allows the development team to use the same kits. This eases the programming of
the different units and decreases the cost.
The amount of memory that will be needed for the wall switch like the remote unit is not
yet known. The memory used will be setup in a similar fashion as the remote controls
microprocessor. The ROM or FLASH will house the main software and the RAM will
hold temporary data. The complexity of this unit will be less robust that that used in the
remote and will as a result use less memory.
The amount of power needed to run the microcontroller is important but not as much as it
was for the remote control unit. This microcontroller will be powered from the AC line
and thus there is no concern for battery life. Even without the battery concern a low
power controller would still be better suited to lower the cost of the user’s electric bill.
The controller for the wall unit would incorporate the standby modes but would not need
to initiate the hibernate mode.
For the project at hand the ideal specifications for the microcontroller would be:
 At least eight general input/output pins
o Supporting Asynchronous communication (Serial)
o Allowing for Clock Line to sync data flow
 Familiar Development Environment such as the C programming
language
o Virtual development and testing
 Combination of Memory types
o FLASH or ROM for program
o RAM for temporary data
 Low power consumption
o 1.8V ideal
o 3V acceptable
 Low cost for chip and development tools
A basic diagram of the microcontroller and component interface is as follows:
23
Power MOSFET
1
MicroController
4
2
Wall Switch &
Dimmer
ROM/FLASH
RAM
RF Transceiver
ALU
PC
Voltage Source
Figure 20: Wall Unit Microcontroller Interface
End-User Programming
To set the different light switches to communicate with the remote unit end user
programming may be incorporated onto the units. This would allow the user to set the
room and light number to the proper remote button. A few methods to achieve this have
been encountered two of these are:
 Manually set addressing
 Preset addressing
For the addresses to be manually set there is a need for a teach button on the remote
control and a learn button on the wall unit. The process that would be employed to set
the address is as follows:
1. Press the Learn Button on the Wall Unit
a. Wall transceiver set to a default value
2. Press the Teach Button on the Remote Control
3. Press the Corresponding Room and Light Buttons
a. The Desired Address is then set into a Packer
b. The Packet is Transmitted from the Remote
c. The Packet is Received at the Wall
i. The Desired Address is then Set as the New Address
24
This would require the microcontroller to have a set address table stored into the main
programming, each address relating to a specific room and light number. To keep the
addresses saved in the wall unit in case of power failure one would have to store it in the
ROM/FLASH memory of the controller. This method allows the end-user to purchase
generic wall switches as needed and place them anywhere in the residence. The
downside is that it requires much more programming and has a large chance for error
during design.
Prepackaged addressing would work much differently and require no end user
programming. The remote control unit would still have the preset table of room/light
addresses. The wall units would have preset addresses in the programming allowing the
users instant usage when connected. When the user would purchase the wall unit they
would specify room and light number desired for installation. This method allows cuts
down on development time, in/out pins used, and time between installation and usage.
On the other hand it also requires the user to purchase specific wall units and for that wall
unit to be placed in the proper AC power box. If the user picks up the wrong switch
number there may be lights in the house falsely operated with one button. If the unit is
placed in the wrong room the user may think the system is defective.
If time allows the method that would be incorporated into the system would be to
manually set the address of the wall units. This allows greater freedom from the end user
and reduces the risk of over/under stocking a specific wall switch model. However, due
to the time constraints of the course the design may have to integrate the preprogrammed
addresses method.
Radio Frequency Communication
The following sections pertain to the Radio Frequency system to which the wireless
lighting system takes advantage of. There are multiple options to which the design of the
project can flow through. As the project is based on allowing for a wireless signal to
control lighting, the transmission and reception of the signal proves very important.
Options for the system include different types of technology; Blue Tooth, Zigbee, and
basic RF transmission are discussed in order to determine the best option for the project.
Multiple technologies of interest were considered for the project. Blue Tooth wireless is a
large up and coming RF technology. It is centered on portable go anywhere ad-hoc uses
such as mobile phones, laptop computers, and PDAs. While not brand new the
technology is just now coming into the limelight and becoming widely used. The main
problem with blue tooth usage is that it can only have a maximum of 7 connections at one
time. If the remote were to communicate with all the available lights in a house, Blue
Tooth would not be able to communicate with them. Another draw back of the
technology lies in the usage of the 2.4 GHz band of frequencies. The project is to be
designed for the home lighting system and in many of todays and future homes, wireless
internet networking is enabled over this bandwidth. While Blue Tooth does work through
25
frequency hopping it will still interfere with the Internet connection and reduce the
reliability of the wireless connections for both the lights and the Internet of a household.
Another drawback is that because Blue Tooth is a relatively new technology, it would
create a learning curve and would have a more difficult time with troubleshooting a
problem.
Zigbee wireless is one of the newest RF transmission standards to be introduced to the
marketplace. It works on multiple frequency bands between 900 MHz and 2.4 GHz and
has been introduced as the next technology to propel automation into the future. It does
have a low power standard, long battery life, and an extremely large network capacity to
allow for many connections to one device. The problem with Zigbee wireless is its
unfamiliarity. Introduced just one year ago, only now are companies beginning to
produce products that work with this technology. The project will be difficult enough as
it is to create and work properly, but incorporating a new technology that is not taught in
the classroom would only slow the project down and possibly cause issues due to a
smaller ability to troubleshoot.
Another type of technology for wireless transmission involves Infrared transmission.
While infrared is a reliable and proven technology, it lacks the type of functionality that
our project wishes to achieve. Line of sight transmission is what infrared is based off of
and the project wishes to be able to control lights in all parts of the rooms. This means
transmission through walls, doors, and whatever else a house will contain. This would
simply be too much interference to use infrared in the design of the project. Design of the
project does not warrant a point and click device but rather it should have the ability to
turn a light on from another room. Infrared simply will not be able to handle this issue.
Range of the technology is the next consideration for the project. Most wireless receivers
and transmitters will have either small range, on the order of millimeters to centimeters,
or no transmission range at all. With that said, the required technology for the project will
be to incorporate an antenna. The trick will be to find a small, cheap antenna which
works well with wall interference because the nature of the project requires small
implementation into the wall and transmission through these walls.
After considering all the different types of RF transmission technology the design of the
project will be based on simple RF transmission utilizing the 933 MHz range. This will
suite the project the best as it will have a relatively low cost and ease of finding what is
needed for the project. This will be important in the event that chips are blown or need to
be replaced quickly. Another important aspect of using this technology is familiarity.
Classroom teachings and professor experience will help us to reach our finished project
in a more timely manner and be able to have confidence in how it works and its
reliability. This is also important as understanding how the signal is transmitted through
the devices will allow us to more easily communicate with the microcontroller.
The following sections pertain to how the RF communication needs to be designed
around and the research through which it is based on. Below is a block diagram
describing the simple design of the RF transmission loop.
26
Figure 21: Block Diagram of Simple RF Transmission Loop Circuit
Antenna
Sending and receiving of the signal begins and ends at the
antenna. This means that the antenna plays an important roll in the
research and design of the lighting system.
Antennas vary in size shape and form to collect a variety of
different electromagnetic waves. Design aspects of the antenna
include the following:







Small size
Range
Low cost
Interference issues
Signal transmission and reception
Interfacing with receiver and transmitter
Low power consumption
The antenna will be required in two parts of the system, the
remote and the in wall setup. The range for both devices should
be the same, as a remote should be able to communicate with its
receiver from one end of the house to the other. This will require
the range of the antenna to reach at least 30 meters. This will be
preferable because even if the distance is less, as the case would
be most of the time, the strength of the signal will more easily
pass through obstructions and interference. The type of antenna
will determine its size and range. Preferably some type of chip set
that interfaces with a receiver and a transmitter instead of two
separate antennas. The simple whip style antenna is most similar
Figure 22: Antenna
Design Styles
27
to what everyone today will notice as an antenna, it looks like a pole standing tall to
receive a signal. It will work as it can transmit and receive from any angle of placement.
Parabolic antennas will not work as this would be similar to infrared’s point and shoot
technology because they act as dishes and need to be pointed at there sending and
receiver points to work properly. The third type of antenna is the loop style. They are
commonly printed onto PCB boards. The best type of transmission will be through a
surface acoustic wave (SAW). This type of transmission allows for any angle of
placement and the signal to be transmitted anywhere. This type of wave can be used by
an antenna that is incorporated into a microchip to provide for a smaller all in one chip.
Integrating the antenna will be the best option as this will greatly reduce the size of the
device.
Receiver
The purpose of the receiver will be to input from the antenna and output to the decoder
which then sends the signal to the microcontroller. When this happens the receiver must,
if required by the transmission signal, demodulate the signal and output to the
microcontroller. The following are the issues with which the receiver must take into
account.






Low power consumption
Demodulation of the signal
Input pin from antenna
Output pin to decoder or microcontroller
Size considerations
Bandwidth considerations
The receiver is part of a system which must remain reliable and keep to a small size. The
system is designed to be integrated into a wall mount switching system of a house. This
design must maintain light power consumption as most power needs to be transferred to
the light itself. The actual power consumed should be attempted to match that of other
chips so as not to let the circuit become overly complicated. Also, the size of the chip is
important as it is part of a larger system of chips that will add up in size and power. The
chip must also be able to handle a certain minimum bandwidth as the signal must contain
the information about which light to turn on or off and data on how to pass the signal on.
Demodulation of the signal is a primary concern of the receiver. This is the main purpose
of the receiver and can be done in a variety of ways. The type of demodulation should
match that of the modulation of the transmitter. This modulation is discussed later in the
transmitter section.
The receiver will also need to only receive signals that are meant for the device. This
allows for the device to only communicate with other units in the system. Since this is a
home automation device, other wireless devices such as a garage door opener might
interfere and send a signal to the device. In order to counteract this effect, the receiver
28
should have some kind of ID on the device. This can be done through the decoder (see
next section) or with RFIDs. The idea behind the Radio Frequency Identification is that
the signal contains some type of encryption pattern. This pattern is detected by an RFID
antenna and is then comprehended. If the patterns match then the signal is let through,
otherwise the transmitter ignores the signal. While this would be practical for the wireless
lighting system, it is not needed for success and proper security can be achieved through
the decoder. This will allow for less work and a simpler device as the decoder will serve
two purposes and eliminate any encryption issues we may have. A third option of
addressing comes in the form of the microcontroller assigning the addressing to the chips
though serial communication. This allows for a programmable option instead of the
hardwired option. In the case of commercial production this might allow for larger scale
systems to be more easily created because the unit can be created generically and then
programmed.
Decoder
Following the receiver is the decoder. The basic principle of the decoder allows for
input from the receiver and output to the microcontroller. Its basic function takes the
demodulated signal from the receiver and translates it into something which the
microcontroller can read and interpret. Decoder considerations are as follows:





Low power consumption
Proper translation of the signal
I/O pins
Small size
Bandwidth
The decoder could be integrated into the receiver, as this will allow for less area
consumed by the chips and a shared power supply now incorporated into one device.
Also important to the decoder is its ability to
translate the information so that the microcontroller
can interpret the information. The main purpose to
using a decoder is that they are easy to find,
understand, and incorporate into circuits. Previous
background in digital electronics will allow for the
incorporation of the decoder into the project.
Strong considerations in choosing a decoder are
based on the data bits that it can transmit and its
ability to hold some type of addressing system. The
amount of bits that the decoder can handle is
important to the design of the project because
information must be sent that contains the address
Figure 23: Decoder Addressing
29
or ID of the light, whether is should be on or off, a status indicator, and to pass the
signal onto the next light, similar to ad-hoc networking. See later section on Packet
Transfer through the RF system. With this in mind the decoder will be required to
contain pins for address lines. These pins are used to verify that the decoder should be
receiving a certain signal from a transmitter and not from the garage door opener.
Some types of decoders contain 8 address lines allowing for 264 different
combination of addressing. The method the decoder uses for this is to receive input,
pass the input through the addressing, then if the address matches the device it
proceeds to decode the signal and is then outputted. If the signal does not match the
addressing than the device will reject the signal and return to its previous state.
Transmitter
RF transmission parallels that of receiving. The transmitter inputs information from an
encoder or in the case of a combination encoder transmitter, from the microcontroller.
This information is then modulated and sent to the antenna for transmission. Proper
considerations for transmitters are as follows:







Low power consumption
Modulation of the signal
Size limitations
Bandwidth
Proper I/O pins
Output Power
Low interference
The transmitter is but a simple piece of the puzzle to send the RF communication. It is
important that its power dissipation matches that of the chips around it. Commonly the
transmitter chips run from 3V to 5V for power supply. This type of consumption easily
matches that of the receiver, microcontroller, encoder, and decoder. In keeping with the
theme of chip similarity, the size should also be kept to a minimum. This idea is
important in that it allows for the unit to fit more readily into the wall without damaging
surrounding areas.
Proper modulation through the transmitter plays an important roll of the device. The main
purpose for having the transmitter is to create this. Modulation of the signal would be
chip based. Modulation comes in several forms usually based on AM or FM. The best
type of modulation method for sending control signals to devices is labeled On-Off
Keying (OOK) or Carrier Present Carrier Absent (CPCA). This type of modulation is
based on a voltage high or low, a logic one or zero in digital terms, and is commonly used
to send signals telling devices to be on or off. This type of modulation has several
advantages. Low power consumption as the signal only draws power in a high logic state.
Therefore at a 50% duty cycle, the power consumption is ½ of what is supplied. OOK
30
modulation is relatively simple and thus requires less components leading to a smaller
size.
Signal interference is a major concern of the RF transmission research and design of the
project. Since the signal is traveling through free space it can have numerous attacks on
the integrity of the carrier. In order to reduce interference the transmitter should provide
enough power to the signal. This will provide for a greater range of the signal, which in a
crowded space, such as a house, will allow the signal to pass with less noise. The walls of
the house will of course reduce the range but the added power helps to process the signal
through them. A transmitter range of 300ft should be appropriate as most houses are less
than 100ft in length.
Encoder
The transmitter’s accomplice is the encoder. Its basic job description parallels that of the
decoder. Upon input the chip will encode the signal for transmission. This is basically a
process of preparing the signal to be modulated by the transmitter. The following design
ideas should be incorporated:




Low power consumption
Proper translation of the signal
Small size
Bandwidth
Power consumption for the chip should be kept to a minimum and attempted to match
that of other chips as this will allow for a simpler circuit. With this kept in mind many
encoders run in the 3V-5V range which would be easily plausible for the design of the
circuit. Size should be taken into account as the chips will begin to add up and increase
the complexity and girth of the board. This is of course important as it will fit into a
remote and wall unit with limited space.
The process of encoding is important to signal transmission because it takes all the highs
and lows (1s and 0s) and translates them into a single block of code. This block of code
can then be outputted to the transmitter. Encoded signal transmission occurs in two ways,
pulse width modulation and serial data transmission. Pulse width modulation reads both a
high and a low in one clock cycle and identifies it based on the order of the 1 or 0. Serial
simply transmits a 1 for high and a 0 for low. A major problem that can occur with
transmission is edge jittering. This error is caused by noise and can allow for false
interpretation of the signal at output. Serial communication is more noise resilient and
therefore is better suited for use in a wireless system. It will also be easier to
communicate with the microcontroller in this fashion.
This figure demonstrates a few important topics. In regards to serial communication, the
encoder reads on every set interval high or low. This allows for reduction of false
readings due to edge jittering because if the edge does shift it will still be read in the
31
correct manner. Next, if this were the input into the encoder, than the encoder would
proceed to create a block of data to be sent to the transmitter. The following code could
be translated into a three byte block of data: 0110 1001 1010.
Figure 24: Input to Encoder
Packet Transmission
Packet Transmission of the signal creates an important series of problems to be
solved by correctly choosing devices and using proper programming methods to
transmit the signal. The first property of the signal to be considered is the size of the
packet. This refers to the number of bits that the packet of information will contain.
This certain size is important because of the decoder and encoder, these devices can
only handle up to a certain amount of information before it cannot convert the signal.
Also, the size of the packet will affect the receiving and transmitting ends of the
signal. The receivers and transmitters operate at certain frequencies of transmission.
Common types are 433 MHz, 933 MHz, and 2.4 GHz. The higher the frequency the
more bandwidth that the signal can contain but will require more power output and
higher cost. The range also decreases as the frequency increases unless more power is
applied. Since the data being sent for the project is simply control signals of on or off
the bandwidth required will be small. For these reasons it will be a good idea to use
the 433 MHz frequency chips. They will allow for the cost and interference to stay
low and also for the range to stay high.
Packet Transmission size is also important in another
aspect related to interference. When data is sent
through an RF signal, many forms of interference
affect it. The first type of interference pertains to
other signals in the area using the same frequency to
transmit. Since RF transmission is becoming more
and more popular among devices, the airwaves are
becoming more like a traffic jammed highway.
Signals are sent and received but bits and pieces may
be lost due to RF waves propagating into each other
and causing loss of data. Another form of interference
has to do with the walls of the house. Since the signal
must be transmitted from one end of the house to the
other, there will be reflection of the signal off the
walls that in tern will cause signal break-up and
interference. The best solution to all of these
Figure 25: Noise reflection
from walls and airwave traffic
32
problems will be to create smaller packet sizing. This gives possible interference less
chance of affecting the signal because there is a smaller amount of signal to breakup.
The second possibility to greater clarity at reception is stronger power output from the
transmitter. The more power that the signal is sent with the more difficult it is to
break the signal up. This will be something that is more difficult to accomplish
because the chip has a limited power supply range and thus can not increase output
range significantly.
Packet Transmission Protocol
Protocol for transmission defines what is actually carried in the signal. This protocol is
important because it defines the communication between transmitter and receiver. This is
comparable to communication between two people, you must be speaking the same
language or develop a system for understanding or else misunderstanding will occur.
What this means to the packet protocol is that the information that is sent must contain
identifiers that will allow for correct interpretation of the data. The following list pertains
to the protocol for packet design
1. The first block of information should contain some type of turn-on code so that
the receiver can begin to recognize an incoming signal
2. Second, the packet should contain some type of error checking block. This block
allows for the transmitter to embed some type of information that can be
compared at the receiver end. If the information matches up correctly then the
receiver can begin interpreting data. There are three types of error checking:
a. Parity Check: Calculates if the number of 1’s adds up to be odd or even
and adds a parity bit to the information that identifies which value it is. On
the receiving end 1’s and 0’s are added and checked against the parity bit
to match odd or even. This check is the easiest to implement but least
efficient as it can only catch an error 50% of the time. This is due to the
check only catching errors when the bit amounts are off. There could be
the same amount of 1’s in both signals but in different orders, this would
create an incorrect signal reception.
b. Checksum: Adds the values of the bytes together and truncates the sum to
the desired bit length. This allows for the receiver to match this sum and
allow for further processing. The downfall to this method is that if the data
is out of order but still adds up to the same amount it will pass incorrect
data.
c. Cyclic Redundancy Check: The CRC method works based on the
checksum method whereas it adds up bytes and compares them. The main
difference is that each individual bit is added and then the sum is divided
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by a certain number. The remainder is sent along with the packet and
checked at the receiving end the same way it was sent. This is more
complicated than the previous two checks but allows for the most
accuracy.
The actual design of the packet will depend on time and programming constraints
and therefore choosing the process of error checking will be left for later.
3. The third block of information contained in the packet is the addressing of the
signal. This addressing will determine if the signal being received is actually
meant for the receiver.
4. The final block of code is the actual data being sent over. If the packet passes all
the previous checks then the data will be interpreted and sent on to the
encoder/decoder pair and finally onto the microcontroller.
Figure 26: Generic Packet Design Block
Transceiver
Transceivers are an important chip type to be considered for RF communication. The idea
is that the transceiver combines the transmitter and receiver to form one chip. This
presents some interesting possibilities for the project. With two chips combined into one,
space will be saved which is important because of the size restrictions of the remote and
wall unit. Also, power will be shared over one chip instead of two. The next benefit is
that the chip will have an internal switching device for the receiver and transmitter. This
is a benefit because with a separate receiver and transmitter you need two antennas or a
switching device that controls the two output signals. This will again save space because
it eliminates a chip. Disadvantages of the transceiver include an upgraded cost and
encoder/decoder interfacing. Since all these chips are placed into one, the cost of the
transceiver chip is greater than that of all of the separate chips combined. Next, a chip
with an encoder and decoder integrated into the circuit would need to be found. Another
option would be to see if this process is done internally. Overall it would allow for less
control of the signal passing through the chip. If a transceiver were to be used many of
the same goals for the chip would be assessed. Low power consumption, size, cost, I/O
pin configurations, modulation and demodulation methods, and bandwidth are all
considerations that should be taken into account when choosing the chip in later design
for the project.
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Wall Dimmer
In order to dim a light you must limit the power going to it. This can be accomplished by
limiting the voltage or the current. The simplest way to do this is to put a resistor in the
circuit, but this method is highly wasteful of energy and generates excessive heat. A
better way to do it would be with solid state devices. The devices looked at here will be
Semiconductor Controlled Rectifiers, TRIAC’s, and Insulated Gate Bipolar Transistors.
Note that these methods are not limited to the dimming of lights, but can be applied to
any power limiting situation. However, for the purposes of this project only the dimming
of lights is required.
Semiconductor Controlled Rectifiers (SCR’s) are devices (Figure 27) that act very
much like a diode with a control line. It will only conduct when the control line is active
and it is forward biased. Therefore, the power passing through it can be limited by
varying the amount of time the device is “on” through the control line. For AC power, an
SCR on its own will only pass a maximum of 50% total power because, regardless of the
control line, it’s off when it’s reverse biased. For this device there is little to no wasted
power and they are typically made with voltage ratings of 50 to 2500V and a current
rating of up to 3000A. In order to implement an SCR, and have a maximum of 100%
power passed; the design would have to include two of them wired in inverse parallel.
The control lines would have to be digitally controlled, or with a complicated RC circuit.
Figure 27: Semiconductor Controlled Rectifier
A TRIAC, or Triode for Alternating Current, is the equivalent of two SCR’s joined in
inverse parallel except that the control gate is now a trigger gate and, once triggered, it
will conduct in either direction until it reaches zero voltage and turns off. This device
can be used for light dimming by triggering the TRIAC at a specific point in the AC
power curve, at say the peak of the sinusoid. It would turn off once the voltage crosses
zero, so then the controller can trigger it again on the negative cycle at the same point.
Doing this would pass 50% of the power through the line (as illustrated in Figure 28).
The amount of power passed can be adjusted from 0-100% by triggering the TRIAC at
various points on the AC curve. This device is better suited to the project’s needs than an
SCR because it typically has a current rating of up to 20A and costs less.
Figure 28: 50% Power Passed
35
The triggering line for the TRIAC can be controlled with an RC circuit or a
microcontroller. The time constant in the RC circuit would be what controls when the
TRIAC triggers and can be adjusted via a variable resistor, which is how most rheostat
style wall dimmers are controlled. A microcontroller (MC) can be used to trigger the
TRIAC only when the period of the oscillating signal is known. Once the period is
known, the MC can be programmed to trigger the TRIAC at any point desired, thereby
giving more control than a mechanical rheostat.
A major consideration needed to be taken into account for with TRIAC’s is their use with
inductive loads, such as electric fans. When there is a sudden interruption of current in
an inductive load it can lead to a sharp rise in voltage across the dimming circuit. This
voltage spike could prevent the TRIAC from turning off at the end of each half cycle or
cause it to outright fail. To prevent this the design would need to use what is called a
snubbing circuit, which would block or suppress these voltage transients. For AC
circuits, a snubber can be made simply from a small resistor in series with a small
capacitor. This would, however, add to the size of the circuit, which may prove
troublesome for the design of the wall unit, but not likely.
The third and least practical option for dimming is by using an Insulated Gate Bipolar
Transistor (IGBT). It is effectively a FET (Field Effect Transistor) controlled Bipolar
Transistor, so it combines fast switching of a FET device with the high current and low
saturation voltage capability of bipolar transistors. This device is more commonly used
to control switched mode power supplies, but the same principles can be used to dim
lights. It does this by rapidly switching the load current on and off thereby stabilizing the
output voltage, or “dimming” the sine wave, if you will. IGBT’s are relatively new
(invented in the 80’s), so they are more expensive, but they do provide higher efficiency
and smaller size than SCR’s or TRIAC’s.
Liquid Crystal Display (LCD)
The liquid crystal display will be incorporated into the remote control unit of this design.
The purpose of this component is to give the end user visual text feedback of various
functions that will be incorporated into the remote. While researching the different
displays there were a few specifications that needed to be considered.
 Interfacing with the Microcontroller
 Size
 Screen Lighting
 Powering the Display
The microcontroller used for the remote will manage the display as well as the rest of the
onboard components. The display will need to receive the data to be shown onto the
screen from the remote’s microcontroller. One of the biggest concerns when interfacing
the LCD is the number of in/out pins that will be required. There must be enough pins on
the controller to satisfy the need of the LCD for proper data transmission. Many of the
36
display modules investigated have ten pins that may be used. For the ten pin models
there are eight data bit pins labeled “Data bit 0” through “Data bit 7”, a read/write pin,
and a “DATA” pin that is an instruction code pin. If there are not enough pins available
the LCD can be set to use four of the eight available data pins. In that case it would be
operating in four-bit mode rather than eight-bit. There have been models found that only
require two and four pins from the controller to properly display text onscreen.
Synchronizing the data being sent is also an issue. The data must be sent at a proper
speed for the information to be seen properly. To do this a serial communication can be
used or a clock line emitting from the microcontroller can be used to make sure the
components are in step with each other.
The size of the LCD is also an important factor when considering what product to
purchase. There are two aspects of size to consider, the size of the display and the unit
(LCD and circuit board with pins). The LCD display size needs to be large enough to
show the output text from the various functions that may be encountered. The project
will have a query button that will allow the user to see what lights are on within the
residence. Thus the display needs to have enough space to show the room name and
lights that are on in that room. There will also be text showing what light is currently
being turned on/off. Most of the market LCD’s show how many characters can be shown
by a measurement of rows times columns (such as 2x16). There are many different
combinations of rows and columns to choose from, allowing great freedom to choose a
proper size. Of the many different sizes the one that seems to fit this design project best
is a 4x20 (four rows with twenty characters per row) display. This will provide sufficient
room for the information to be clearly shown to the end user. The other size factor to
consider is the size of the complete LCD unit (length, width, depth) including the pins,
and any circuit board that may be attached. This is a major factor when choosing the
display because it will add to the size of the remote control unit. Placing a larger yet
cheaper display in place of a smaller and more expensive one may make the control unit
large and unsatisfactory for the end user. The size difference may also require the remote
unit layout to be redesigned to prevent it from being unbalanced and bulky. An example
of a mid-priced 4x20 character LCD dimensions is as follows: 98x60x15 mm.
Lighting the LCD is another topic to consider when choosing a display. A question to
ask is will the display be in lowlight areas during some time of use. If the LCD will be in
a location of poor ambient light then one would be best off selecting a display with a
backlight. For the project at hand it would be useful to the end user to have a backlit
LCD for the remote because the unit may be used in a room when the light is off. There
are variety of colors and controls for backlights available to be incorporated within the
remote. The different color lights available will run at different voltages and provide
different levels of contrast on the screen. When selecting the LED backlight one would
be concerned with the voltage required to operate the light, and how much contrast is
provided. One way to control the backlight is to turn it on at all times the display is in
use. This method ensures that there is enough light. This is a waste of power and in most
applications unnecessary. Another way to toggle the light on/off would be to have the
light turn on every time the end user is interfacing with the remote, and turn it off after a
set amount of time after no data is sent to the display. Another way to control the
37
backlight is to use a photo diode as a sensor to only turn on the light when the remote is
in an area of low light, and turn off the light a set time after the interfacing is completed.
The last option would be the best suited for the design project for a many reasons. The
photo diode would allow the LED to be turned on only when needed and would conserve
power usage. This is favorable since the remote would be powered by a battery cells.
Power is this designs biggest concern for operating the LCD. This is because the display
will be incorporated on the battery operated remote unit. As mentioned earlier the remote
will be powered by onboard battery cells. This is important because the battery cells will
need to power not only the display but also the LED backlight, the microcontroller, and
the RF transmitter. A lower power LCD would be ideal for this design. A mid priced
display as to the specifications noted earlier would require approximately seven volts of
DC power. If one was to power this unit using standard AA batteries it would take a
minimum of five batteries making the unit cumbersome. One also wants the battery cells
to last as long as possible. To achieve the longest battery life the design project will
incorporate many different power conserving schemes. The most obvious is to select an
LCD that would allow for minimal power usage while operating. Controlling the
backlight with a photo diode as mentioned earlier will extend the battery life by removing
the power consumption of the LED backlight until it is actually needed. Another method
to be employed in the project is to simply turn off the display when there in no user
interfacing the remote. During this time the entire remote will go into a sleep mode
decreasing the usage of power and prolonging the battery life of the unit greatly.
Reviewing all of the points found during research this design project would
benefit the most from an LCD with the following ideal specifications:
 4 to 8 pins to interface with the microcontroller
 4x20 character display
o with the smallest physical dimensions possible
 Backlight LCD display
o High Contrast
o Controlled by a photo diode
 Low power consumption
o Sleep mode available
A higher cost LCD that meets the above specifications may benefit the design more than
a cheaper one. The cost would be justified by a better interface for the end user, smaller
battery cells needed, and a greatly extended life for the batteries.
Speech Recognition
Speech recognition has come a long way since its introduction and is now surprisingly
easy to implement. These systems take spoken audio as input and then process it to
recognize words or even the speaker. The recognized words can then be used as input to
a control system, which is the application here. There are still a few issues which must
38
be considered when implementing this technology. Modern systems can be classified
into two categories: speaker independent and speaker dependent. In addition to the
categories of speech recognition, there are also three styles of speech: isolated,
connected, and continuous.
Speaker Dependent systems require the system to be “trained” by the individual(s) who
will be operating it. This means that the user will have to program the lighting system
with the words to be recognized. These systems are capable of achieving a larger
vocabulary and greater accuracy (up to 95%), but that accuracy is limited to the
individuals who trained it. This system would be better for the design’s purposes, but
would be harder to implement.
The other system, Speaker Independent, does not require user training and will work with
any speaker. It is designed to respond to the word instead of the speaker, so it must be
able to handle a larger variety of speech patterns such as accents and other various
nuances. Because of this the word vocabulary is usually smaller, but high accuracy can
still be maintained. Speaker Independent systems are easiest to implement, but their rate
of error for larger vocabularies can be troublesome. Luckily the vocabulary required for
the lighting system will be small (fewer than 7 words), so this may prove to be the better
system.
Isolated speech recognition systems can only handle words that are spoken separately.
As such the user must pause between each word or command spoken. This is the most
common form of speech recognition available today and is all that is required for this
project.
Continuous-capable speech recognition systems are able to understand naturally spoken
conversation. These kinds of systems are the most erroneous since a simple phrase such
as “Hi, how are you doing?” can be misconstrued as “Hi, howyadoin?” if spoken too
quickly. This is the most advanced form of speech recognition and is therefore the most
expensive. It is doubtful that this mode of operation will be used, even if it is available.
Connected is the median between isolated and continuous speech recognition. It works
like isolated systems except instead of the recognition of a single word it can recognize a
small string of them. This may prove beneficial in the design of the lighting control
system, but again it is doubtful that it will be used.
The speech recognition systems available today can be purchased in stand-alone,
software, or integrated solutions. Software solutions require a microprocessor and are
usually found on home computers, so it will not be required for this project. Integrated
solutions are coupled with a microcontroller and digital signal processor. Stand-alone
solutions can only process and recognize speech. Their output must still be run through a
controller to have any benefit. They are the simplest of all these devices and are ideal for
this project.
39
One such stand-alone device is the HM2007 speech integrated circuit. This device is
incredibly easy to implement which makes it a very attractive option. To program it you
need a numeric keypad, an LED display, and a microphone. Enter a number, then speak
the word to be programmed, and that word is now assigned to the number. The chip is
always “listening” so whenever it picks up that word again from the microphone it will
output the associated number to the LED display. Data for the chip is stored on a
separate RAM chip, so the vocabulary size is expandable. The HM2007 operates as a
speaker dependent speech recognition chip, but it can be programmed to simulate speaker
independence. This is done by assigning the same word to multiple addresses, spoken by
different people. That way there is a good probability that the chip will understand the
word spoken from any source. This design can be adapted to the projects needs by
connecting the output of the chip to a microcontroller. As a bonus this chip is very low
cost.
An example of the other option under consideration (integrated) is the RSC-464 speech
recognition microcontroller by Sensory Inc. This chip is a fully featured 8-bit
microcontroller as well as speech recognition unit. It is programmed through its software
development kit. This chip has many more features than the HM2007, such as Speaker
Dependent/Independent processing, Text to Speaker Independent capability (Text words
can be used to program recognized speaker independent words), and even a music
synthesizer, among others. The capabilities of this chip are far beyond the scope of this
project so it is doubtful it will make it past the planning stage. Since it has a built-in
microcontroller this would be the only controller needed for the wall units.
In order to properly implement any speech recognition system a few considerations must
be taken for microphone placement and housing. The microphone must be mounted flush
with the surface it is attached to, otherwise, if there is an air space, acoustic resonance
can occur which will greatly diminish recognition. The area in front of the opening for
the microphone should be clear of obstructions and the opening itself should be at least
5mm wide. Also the surface the microphone is mounted to should be as thin as possible
and no greater than .7mm. For optimum performance the microphone should be
acoustically isolated form the housing. This can be accomplished by surrounding the
microphone with a spongy material such as rubber or foam. The purpose of the last step
is to prevent noises from the handling of the object from interfering with operation; it
applies to the lighting control project by preventing noises from traveling through the
house to the microphone. Lastly if the chosen speech processor does not include an
amplifier then one must be designed to amplify the microphones signal. Otherwise
performance would degrade by a factor of 4 after the audio source has moved 6-12 inches
away from the microphone.
40
Personnel and Bibliography
John Bambace
John Bambace is senior Electrical Engineering student at the
University of Central Florida. With Electrical Engineering as the
original major for John, he is pushing through all that UCF has to
offer. Linear Controls, Electronics I & II, Electromagnetic Fields,
Signals Processing, Networks, Digital Circuits, C++ and assembly
programming, and Semiconductors are all important fields in which
John has studied and performed well in, holding a 3.4 GPA after three
years. John is committed to school work but is also involved in many outside
activities. John has been the Juggling Club at UCF Co-President for two years,
helping to develop the club into a larger more performance oriented club. Shows span
the Rosen campus and the student union’s Pegasus Ballroom. John is also a
committed member to the UCF Ultimate Frisbee team. The team travels all over the
south east and is an up and coming name in the college Ultimate world, seeding well
at regional’s only three years after being founded. Additional interests include water
sports such as surfing and windsurfing. These different aspects help in creating a well
rounded student that is suited to be a part of a great senior design team.
Eric Marshall
Eric Marshall is currently a senior in the Electrical Engineering department
at the University of Central Florida and plans to graduate in Spring 2007.
He is a student of the Burnett Honors College and has graduated from the
LEAD Scholars program, while maintaining a 3.8 GPA. To date, he has
completed Linear Controls, Electronics I, Electronics II, Signal Analysis
Communication, Electrical Networks, Networks and Systems, Digital
Circuits, Computer Engineering, Engineering Analysis, Statics, Dynamics, Digital Signal
Processing, and Semiconductor Devices. His previous work experience includes
employment at the Burnett Honors College and at Advanced Laser Systems Technology.
For the Honors College, Eric was a team leader to 17 incoming honors freshmen. He was
responsible for governing their behavior and effectively serving as a mentor for their
transition into the college lifestyle. At ALST, Eric worked as a technical writer for laser
manuals and for procedures used by ALST employees in the design of the lasers. He was
also a CADD designer for designing parts integral to the manufactured lasers. Eric
gained this experience from his time at Edgewater High School, where he was student in
the Engineering, Science, and Technology magnet program. After excelling through his
high school academics, Eric graduated 9th out of the 628 students in his graduating class.
Among Eric’s more noteworthy achievements is the fact that he became an Eagle Scout
at the age of 13. Following graduation from UCF, Eric plans to go to graduate school
and pursue a Masters degree.
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Mike Segarra
Michael L. Segarra is currently pursuing a degree in Computer
Engineering from the University of Central Florida, Orlando Florida.
Expected date of graduation is December of 2006. Has knowledge of
COBAL, HTML, C, C++, Visual Basic, Java, Intel Assembly, Motorola
Assembly, and VHDL programming languages. Projects include writing a
display program and a memory management program using Motorola
Assembly language for the 68HC11 microprocessor, writing a client/server application
that communicated over the internet and sent data over an RS232 communication line on
the server computer, and participating in a group project for an emergency alert system
for mass communication via cell phone text messages. He also has leadership abilities,
and time management skills that were learned during three years of working as a
manager. He is also a member of IEEE.
Drew Yenzer
Drew Yenzer currently attends the University of Central Florida pursuing
a degree in Electrical Engineering since late 2003. He is nearly complete
with his studies and is expected to graduate in spring of 2007. To date he
has completed the following courses: Thermo-Fluids Heat Transfer,
Electrical Networks, Engineering Analysis, Networks and Systems,
Semiconductor Devices, Electronics I, Introduction to Digital Circuits and
Systems, Electromagnetic Fields, Signal Analysis & Communications, Linear Control
Systems, Introduction to Computer Engineering, Electronics II, and Digital Signal
Processing Fundamentals. He has experience in programming a voice
scrambler/descrambler in order to safely transmit audio without fear of interception.
42
Milestone Chart
The wireless lighting project milestone chart shows the various aspects of what is
to be completed for the entire project. The chart lists the approximate timetable for the
labeled blocks over two semesters of work. Each block is equally important and requires
that it be finished in a timely manner. The design team believed this to be the best
sequence for completing the project.
The first semester is predominantly research and design oriented. This is due to
the fact that creating everything on paper and maintaining its correctness will allow the
project to be completed with minor hassle and frustration. Design will be a very
important aspect and will continue on through while construction is occurring.
Construction should be well thought out so as to save money and time. Testing will
require everything from coding the micro controller to making sure the PCB board works
correctly. After all this is completed the final design and project presentation will be
completed and the last of the kinks will be worked out before presenting.
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