DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING
et
Design Document for
Sherlock Breaker: Circuit Breaker Finder
Submitted to:
Professor Joseph Picone
ECE 4512 Senior Design I
Department of Electrical and Computer Engineering
413 Hardy Road, Box 9571
Mississippi State, Mississippi 39762
November 22, 2004
Prepared by:
K. Fernandes, N. Gilmore, D. Irby, and J. McCown
Faculty Advisor: Dr. Noel Schulz
Department of Electrical and Computer Engineering
Mississippi State University
413 Hardy Road, Box 9571
Mississippi State, Mississippi 39762
Email: (kcf4, ndg7, dwi1, jfm5)@msstate.edu
EXECUTIVE SUMMARY
Matching circuits with breakers has often taken a considerable amount of time and a crew of at least two workers.
Sherlock Breaker strives to eliminate the need for lengthy time frames for breaker and circuit matching in
establishments such as houses, apartments, factories, and even hospitals. New products allow for a single person
to do a two-person job in less time. As better solutions are sought, Sherlock Breaker solves the problem in a cost
effective manner. Sherlock Breaker employs multiple transmitters integrated with a microcontroller-based
operating system to match circuits with breakers to not only offer a reliable system, but also to offer a comparable
price to match several circuits simultaneously.
Many technical aspects as well as real world aspects were considered in the design of Sherlock Breaker. The first
constraint involves applicable line voltages for the input of the system. The transmitter operates using the 120volt, alternating current signal already present on the line, limiting the circuit breaker finder to common
household circuits. This large current does not affect other appliances operating on the same circuit because the
duration is extremely short. Each transmitter emits a signal that is read by an inductive probe in the receiver up to
a circuit length of 300 feet. Signal strength is captured and stored by a PIC during a calibration, or scan, cycle for
future use during a read cycle. Sherlock Breaker enhances current product standards by allowing multiple
transmitters to be detected on one circuit. Real world aspects include power consumption parameters. The
receiver uses two AA batteries, at three volts, to power the PIC and the transmitter draws 120 volts from the
receptacle or outlet it is plugged into. The transmitter draws less than one watt of power. A temperature range of
0°C to 60°C is suitable for the circuit breaker finder to operate in, allowing summer and winter use. The receiver
is ergonomically designed to fit into the user’s hand and measures 8 in. x 2.5 in. x 1.5in. The transmitter is
designed to easily fit into a typical wall outlet and has dimensions of 4 in. x 3 in. x 2 in. The receiver parts cost is
approximately $8 and each transmitter contains parts costing approximately $4. The actual retail cost of the
product is $80. Each receiver unit works up to three years before requiring a battery change.
A SIDAC is used to allow the transmitter to emit 20-amp pulses for less than 3 microseconds each. A PIC also
limits the transmitter emissions. Common household wiring lengths and the limitations of the inductive probe
determines circuit length constraints. The PIC reads the signals on the breakers during the calibrate cycle and
stores the maximum signal for use as a basis for comparison of other signals. Multiple transmitters, each emitting
a various number of pulses per second, operate based on an RC time constant determined using simulations. To
meet the voltage constraint for the receiver, two AA batteries and a boost converter are used to create a five-volt
signal that is the necessary operating voltage for the PIC. Each transmitter draws less than one watt of power
because the SIDAC limits the length of each emitted pulse. Each component used in the construction of the
receiver and transmitters is rated to operate between the range of 0°C to 60°C (32°F to 140°F). Receiver and
transmitter casings are determined by the size of the circuitry needing to be housed. The dimensions are
comparable to current products and are the smallest size necessary for proper ventilation and placement of
components. Estimated retail pricing is comparable to products on the market. A battery change every three years
is expected due to the low current drain on the batteries per operation. A fuse in the transmitter is only for user
safety. Sherlock Breaker enables electricians and maintenance organizations to check multiple circuits
simultaneously, cutting cost and need for multiple workers. The circuit matching system will be marketed in
home-improvement stores and electrical supply facilities.
Sherlock Breaker improves the functionality of existing circuit breaker finders by allowing multiple transmitters
on one circuit. Circuit breaker finders currently on the market use only one transmitter. The Sherlock Breaker
system has the ability to locate and discern up to three distinct transmitters connected to one circuit breaker or
multiple circuit breakers. An enhancement to the circuit breaker finder would be the addition of an automatic
power-off circuit. This power-off circuit would be programmed into the PIC and would not cause a price increase.
In order to increase Sherlock Breaker’s capabilities, a socket adapter could be added. The adapter would incur
only a small price addition, keeping the product at a comparable price to other market models. Maintenance
organizations and do-it-yourself homeowners would benefit from Sherlock Breaker because they could label
breaker boxes more quickly and efficiently. Checking to see if each circuit in a given room is on the same circuit
can be done rapidly by simply plugging each transmitter into different receptacles and matching three receptacles
at once instead of one at a time.
TABLE OF CONTENTS
1. PROBLEM………………………………………………………………………………
1
2. DESIGN REQUIREMENTS...…………………………………………………………
2
2.1. Technical Design Constraints...………………………………………………………
3
2.2. Practical Design Constraints.…………………………………………………………
4
3. APPROACH...……………………………………………………………………………
5
3.1. Circuit Breaker Finder Background Information…………..………………………...
5
3.2. Hardware Design..……………………………………………………………………
6
3.3. Software Design..……………………………………………………………………..
13
4. EVALUATION………….……………………………………………………………......
17
4.1. Test Specification……………………………………………………………………...
17
4.2. Test Certification – Simulation.……………………………………………………….
18
4.3. Test Certification – Hardware.………………………………………………….……..
19
4.4. Test Certification – Software …………………………………………….................…
21
5. SUMMARY AND FUTURE WORK………………………………………………….....
22
6. ACKNOWLEDGEMENTS………………………………………………………….........
23
7. REFERENCES………………………………………………………………………….....
23
APPENDIX A: PRODUCT SPECIFICATIONS……………………………………………..
25
Sherlock Breaker
Page 1 of 25
PROBLEM
Since the start-up of the Pearl Street Station of New York City in 1882, electrical power has revolutionized the
way in which the world operates [1]. As households and businesses began to realize the capabilities of electricity,
electronic devices became more common. Engineers and researchers knew the usefulness of electricity, as well as
the hazards and safety risks involved. Excessive current in typical house wiring quickly heated the wire’s metal.
As the metal heated, the wire became more susceptible to melting and having a broken electrical connection.
Although the replacement of melted wire seemed like a nuisance, a more serious issue arose. Over a length of
time, the extreme heat had the potential to ignite flammable surfaces or objects that the wire touched. Fuses
provided an early solution to this problem. Current had to pass through a fuse before the electricity reached its
target device. If the circuit current level exceeded a certain limit, the metal inside the fuse would break and open
the circuit. While this method of detecting line problems accomplished its task, the fuse also had several
drawbacks. Once a fuse was blown, it no longer had any usefulness and had to be replaced by an identical fuse.
Replacement costs became an issue, especially for junction boxes containing fuses of many different sizes.
Another problem involved determining which fuse needed to be changed. The only way to see if a fuse had
blown was to look through the plastic casing to see if a connection still existed. This task proved tedious and
time-consuming for electricians and building managers who had to check every small fuse in a junction box
whenever the power went out.
Electric companies assigned researchers and engineers the task of inventing a more efficient way of cutting power
to an abnormal electrical circuit instead of the traditionally problematic fuse. By the beginning of the 20th
century, circuit breakers had started to replace older fuse boxes. The circuit breaker had several important
advantages to its predecessor. One economic advantage was the elimination of cost for replacing blown fuses.
While a single circuit breaker costs more than a single fuse, circuit breakers cost less when considering
maintenance charges. The more obvious advantage of circuit breakers was the ease of finding the problematic
electrical line. Once a breaker has tripped, the switch no longer lines up with the other breakers in the box. As
the average building size and height increased, the electrical needs of the building increased as well. This rise in
power requirements caused breaker boxes to grow not only in size, but quantity. Electrical installation crews
were tasked with connecting vast lengths of wire with the proper circuit breakers. Electrical wire installations
usually occurred while other parts of the building were being constructed. This construction schedule required
crews to have multiple people working on one circuit. One person would be stationed at the breaker box while
another person was at the target power receptacle. If the breaker box and target receptacle were a considerable
distance apart, communication difficulties between the two workers could arise.
Although the previously mentioned situation involves the original installation of electrical wiring, the process of
making modifications to existing wiring also has similar problems. Electricians installing new equipment on an
existing circuit must often switch off the power to the circuit. The only way to determine which breaker controls
the target circuit is to flip the breaker switches one at a time until a test light plugged into a wall outlet turns off.
This method has the large drawback of requiring other devices on the line to have the power removed also. In
critical locations such as hospitals, an entire wing or floor would have to prepare patients and staff for a power
outage whenever installation work needed to be done. Again, engineers created a more efficient way to solve the
problem.
The market for electronic devices that assist contractors, professional electricians and ambitious do-it-yourself
homeowners has grown as larger electrical products have become available for residential installation. One
invention to solve the specific problem of deciding which circuit breaker controls each circuit uses the existing
electrical wiring as a carrier for a signal going from a power receptacle to the circuit breaker. Different variations
of this idea have been on the market for years. These products include circuit breaker finders and tracers. While
circuit tracers operate independently of the power on the line, breaker finders manipulate the line current to send a
signal. Since similar products already exist, the Fall 2004 Senior Design Circuit Breaker Finder group has
decided to design a product called Sherlock Breaker. Sherlock Breaker greatly appeals to today’s product market
by using better technology and allowing more transmitters than existing models at a competitive price. Today,
breaker finder units range in price from $29 to $70 [2]. The cheaper models have only a light or a speaker as a
means of informing the user that the proper breaker has been detected. The more expensive models include
Sherlock Breaker
Page 2 of 25
a Light-Emitting Diode (LED), a speaker, adapters, and Liquid Crystal Displays (LCD) that display the signal
strength [3]. Some models even have a second LED to notify the user that the device is searching for the signal.
Sherlock Breaker will include a speaker and LEDs to notify the user that the correct breaker has been found.
The proposed project has many aspects that will make it superior to currently available products. Sherlock
Breaker has an advantage of needing only one person to find corresponding breaker and outlet connections. The
person plugs a transmitter into the outlet, then goes to the breaker box and waves a receiver in front of the
breakers until it beeps and the LED glows. This design is more practical for maintenance purposes, especially at
factories where noise would be an issue. Sherlock Breaker overcomes the important obstacles of deciphering a
coded signal sent over power lines. Using a PIC (Peripheral Interface Controller), Sherlock Breaker will be able
to receive a coded signal from more than one transmitter. A PIC will be used to discern the signals from each
transmitter. Each transmitter will use discrete components to send a coded signal, which could be considered to
be a ‘digital key,’ that will be sensed by the PIC in the receiver. Each PIC will include software design for analog
and digital inputs and outputs. Multiple transmitters will be included with Sherlock Breaker and will send coded
20-ampere signals to the receiver. Some models scan the breakers and attempt to find a strong signal. This
approach could lead to errors if a transmitter uses a weak input signal. Sherlock Breaker will be programmed to
distinguish between different signals, so there will be no error. The magnitude of the transmitted signal will vary
along the breakers, so the user must initially scan the receiver across each breaker in the box for Sherlock Breaker
to automatically calibrate itself. The user repeats the scan, and Sherlock Breaker detects which breaker is
transmitting one or multiple 20-ampere signals. Sherlock Breaker overcomes another obstacle by eliminating the
user guesswork involved with a sensitivity knob. Some of today’s models offer a sensitivity knob to properly
detect a transmitter signal. The sensitivity knob is unnecessary in Sherlock Breaker because it uses a
microprocessor-controlled amplifier.
Each transmitter will be approximately 4 in. x 3 in. x 2 in. While some receivers are large and awkward to grip,
the Sherlock Breaker receiver will be 8 in. x 2.5 in. x 1.5 in., a handy, ergonomic size. Most products presently
on the market are similar in size and shape. Also, Sherlock Breaker can be used as a fast, inexpensive way to
label breakers in a breaker box. The transmitter connects to the 120 volt AC signal with a two-prong plug. The
receiver operates using 3 volts produced by 2 AA batteries. The operating temperature range is between 40° F
and 120° F.
The implications predicted for this product’s success affect different groups of people. Sherlock Breaker is aimed
at contractors, homeowners, and maintenance departments. Sherlock Breaker is inexpensive and a marvelous way
to help contractors identify the correct breaker when making repairs or to check their work when constructing a
new structure such as a house or building. Also, new homeowners or someone moving into a home that does not
have a labeled breaker box could use this product to aid in labeling the breaker box. Maintenance organizations at
factories could also use this product to locate breaker connections without the need to shut off equipment.
Students moving into apartments at college who do not want to overload a given breaker could even use it.
Operating Sherlock Breaker is simple. The user plugs the transmitter into the outlet, turns on the receiver, waves
the receiver in front of each breaker, and waits for a beep and LED to light up. There is no sensitivity knob or
confusing readout on a screen. Everything the user needs is included in a convenient multi-part package.
Sherlock Breaker offers a clear and improved solution to a modern problem.
1. DESIGN REQUIREMENTS
The goal of Sherlock Breaker is to improve the features of modern circuit breaker finders while maintaining a
competitive price. Circuit breaker finders are composed of two major parts: a transmitter and a receiver. The two
most significant features that Sherlock Breaker adds to the product market are the usage of a PIC in the receiver
and the ability to use multiple transmitters simultaneously on one circuit. Each transmitter emits a specific code
through existing electrical wiring using an outlet receptacle. The receiver scans each circuit breaker and notifies
the user when the breaker connected to the transmitter has been found. In order to meet the criteria for the
proposed additions, ten design constraints will be employed.
Sherlock Breaker
Page 3 of 25
1.1. Technical Design Constraints
The technical design constraints apply to the software and hardware aspects of Sherlock Breaker. These
constraints contain quantitative values that can measure Sherlock Breaker’s compliance of the requirements. The
five technical constraints are listed in Table 2.1.
1.1.1.
Applicable Line Voltages
Sherlock Breaker is designed to work on only 120 volt, alternating-current circuits. This product is designed for
primarily residential applications. Although this voltage limit reduces the number of applications for using
Sherlock Breaker, the product can still be used for the majority of household circuits.
1.1.2.
Transmitter Signal
The transmitter component of Sherlock Breaker sends pulses over electrical wiring. Each transmitter is
distinguishable by the pulse pattern it sends. Each pulse will not exceed 20 amps over a duration of no longer than
3 microseconds. Although the current drawn by the transmitter is relatively large compared to other common
appliances on the line, the pulse width will be so small that other appliances will not be affected. If three
transmitters are connected to the same circuit, all three must not significantly disrupt other devices on the same
circuit. The shortest pulse width and frequency capable of accomplishing the task will be used in order to reduce
negative effects to other devices. The pulse width and frequency will be determined by the limitations of the
SIDAC and PIC.
1.1.3.
Applicable Wire Length
Sherlock Breaker will work on circuits up to 300 feet long. Very few residential locations have circuit lengths
exceeding this amount. This requirement dictates the maximum distance that the transmitter signal can reliably be
sensed by the receiver’s inductive probe.
1.1.4.
Signal Strength Calibration
Previous circuit breaker finders have relied on an adjustable sensitivity knob on the receiver. Sherlock Breaker
will use a PIC to automatically calibrate the signal strength of the circuit breakers in the breaker box. The user
will depress a button on the receiver while moving the receiver over all the breakers in the box. When the user
releases the button at the end of this scanning cycle, the PIC will store the maximum signal intensity value.
Incoming signals will be compared to this value, and the incoming pulses from the transmitter will be
distinguishable.
1.1.5.
Multiple Transmitters
As mentioned earlier, Sherlock Breaker will improve the functionality of existing circuit breaker finders by
allowing multiple transmitters on one circuit. Circuit breaker finders currently on the market use only one
transmitter. The Sherlock Breaker system will have the ability to locate and discern up to three distinct
transmitters connected to one circuit breaker.
Sherlock Breaker
Page 4 of 25
Name
Applicable Line Voltages
Description
Sherlock Breaker uses typical 120V AC household circuits.
The transmitters will not exceed current pulses of 20A for more
Transmitter Signals
than 3µs.
The receiver can detect transmitted signals at distances of up to
Applicable Wire Lengths
300 feet.
A PIC will automatically calibrate the signal strength of the
Signal Strength Calibration
receiver to eliminate any false responses.
The switch on the Sherlock Breaker system allows it to distinguish
Multiple Transmitters
up to three distinct signals generated by the transmitters.
Table 2.1. Technical design constraints for Sherlock Breaker
2.2 Practical Design Constraints
The practical design constraints refer to the real-world concerns of the Sherlock Breaker. These constraints outline
the effectiveness, competitiveness, and impact of the product on the market. The six practical constraints are listed
in Table 2.2.
2.2.1.
Power Consumption
Sherlock Breaker uses a minimal amount of power for operation. Sherlock Breaker requires three volts, which is
supplied by two AA batteries. The batteries will be housed in the handle of the receiver unit. The voltage supplied
by these batteries will be sufficient to power the PIC processor. Battery life will be 25 hours for continuous
operation because the current drawn across the receiver is only a few milliamperes per operation. The AA-size
battery was chosen for this component because it is inexpensive and common. The 120-volt AC outlet receptacle
being tested will energize the transmitter to draw less than one watt.
2.2.2.
Temperature
This product is suitable for temperature ranges of 0°C to 60°C (32°F to 140°F). This range allows Sherlock
Breaker to function in a variety of climates. The upper end of the scale makes the unit capable of
operating during summer work. The lower end of the scale will serve useful for electrical installations in
frigid conditions.
2.2.3.
Size
Each transmitter measures approximately 4 in. x 3 in. x 2 in. and weighs ten ounces. The receiver measures 8 in. x
2.5 in. x 1.5 in. with a weight of fifteen ounces. The receiver is ergonomically designed to fit comfortably in the
hand with a minimal weight load. The transmitter has a compact size and fits easily into a typical wall outlet.
2.2.4.
Product Cost
The Sherlock Breaker has a comparable cost to current circuit breaker finder models. Sherlock Breaker uses
standard values for resistors, capacitors, and other electronic components. The cost of producing each transmitter
will be approximately $4. The cost to produce each receiver will be approximately $8. The suggested retail price
of Sherlock Breaker is close to $80. This price contains a system including three transmitters and one receiver.
Most of the cost will be concentrated on the PIC in the receiver. Products currently on the market retail between
$30 and $70 and only offer one transmitter [2]. Sherlock Breaker offers multiple transmitters so more than one
receptacle can be tested in a given room.
Sherlock Breaker
2.2.5.
Page 5 of 25
Reliability
The Sherlock Breaker has unparalleled accuracy in its readings. This breaker finder is very accurate when used in
residential applications. The only reasons for a user to open the receiver case are to change batteries or a blown
fuse. Under normal wear and tear, each unit is expected to function up to 3 years before requiring a battery
change. Sherlock Breaker can be used for indoor or outdoor locations in dry surroundings.
2.2.6.
Safety Constraints
Sherlock Breaker complies with UL safety codes and FCC regulations. Each transmitter and receiver
contains a fuse for protection against currents higher than 20 amps that last longer than 3 microseconds.
This safety protection will reduce the chance of a user from being shocked.
Type
Description
Each transmitter runs on the 120V AC outlet
Environmental
Power
while the receiver runs on 2-AA batteries.
The transmitter is 4x3x2 inches.
Manufacturability
Size
The receiver is 8x2.5x1.5 inches.
At $60 the Sherlock Breaker system has
Economical
Cost
comparable pricing with current products which
range from $30-$70.
Accuracy and
The system is very accurate. There is a 3-year
Reliability
Maintenance
warranty on each part of the system.
Fuses on each transmitter and the receiver will
Safety
Safety
protect the user from electrical shock.
Table 2.2. Practical design constraints for the Sherlock Breaker system.
3.
Name
APPROACH
In this portion of the document, the design engineering involved for the construction of the Sherlock Breaker
circuit breaker finder is discussed in detail. Some basic concepts in power, electronics, and microcontrollers are
discussed. In the first section, relevant background information is presented to inform the reader about common
features and methodologies of circuit breaker finders. In the second section, the design obstacles and solutions for
the two major hardware components, the transmitter and receiver, of Sherlock Breaker are explained. The
receiver portion of the project also contains a software component to control inputs, outputs, and logic. The major
software process loops and functions are explained in the third section of the approach.
3.1
CIRCUIT BREAKER FINDER BACKGROUND INFORMATION
The common goal of circuit breaker finders is to match circuits with the breakers that protect them. Circuit
breaker finders operate by using a transmitter connected to a wall outlet receptacle and a handheld receiver. The
user moves the receiver around the circuit breaker box, and the receiver visually or audibly alerts the user when
the transmitter has been detected. Early circuit breaker finder designs used primarily discrete components. While
these designs were inexpensive, they often required much user interaction through the usage of a manual
sensitivity control knob. Newer designs harness the capabilities of microprocessors, but include features that are
too excessive for the average homeowner such as embedded wire tracing. Circuit breaker finders that are
currently on the market can match breakers and electric receptacles that are connected by wire up to 500 feet long
[4]. The designers of Sherlock Breaker had a motivation to include the most useful capabilities of a
microcontroller while retaining many older circuit designs in order to reduce product cost for consumers.
Sherlock Breaker
3.2
Page 6 of 25
HARDWARE DESIGN
The transmitter and receiver hardware design aspects of Sherlock Breaker are discussed in the subsequent
sections.
3.2.1
TRANSMITTER
The transmitter is used to emit a pulse on the 120V AC circuit. The receiver at the breaker can detect the signal
emitted by the transmitter. Two common methods exist for sending a signal from a wall outlet to an attached
breaker.
The first method involves inputting a signal directly onto the line. While this type of transmitter is relatively easy
to construct, the design issues arise when trying to read the signal at the breaker box. The inputted signal is
drastically affected by 120V signal already present on the line. Therefore, the receiver must use a highly sensitive
inductive probe or very thorough filtering processes to properly detect the signal. This problem is only multiplied
when attempting to put multiple transmitters on one circuit and distinguishing the transmitters individually. The
transmitters must emit signals at varying frequencies that also can only be detected by highly sophisticated
receivers.
The second method for sending a signal from a wall outlet to a breaker involves modulating the existing 120V
line signal. By varying the resistance of an electrical load connected to a wall outlet, the current in a circuit, and
therefore the attached breaker, can be set to a specific level. If a large enough current is generated, a detectable
electromagnetic field is produced around the line wire. Although a relatively large amount of current is required,
the amount of time needed is only for a few microseconds each second. One device capable of creating a
controlled current spike is called a SIDAC.
SIDAC
The SIDAC is essentially two Shockley diodes connected to form a diode for alternating current circuits. The
SIDAC is a bidirectional component that has a break over voltage associated with it. When the input reaches the
break over voltage, the SIDAC fires a two-microsecond, 20Amp pulse. The SIDAC fires this pulse on positive
and negative peaks of the 60Hz sine wave coming from the 120V AC signal. As the break over voltage, VBO is
passed, the SIDAC fires, creating a short circuit, allowing the capacitor to charge. Once the capacitor reaches its
peak voltage, it closes, allowing the current to drop below the holding current value. At this point, the circuit is
essentially open and the process is repeated on the negative peak of the sine wave [5]. The SIDAC characteristics
are shown in Figure 3.1.
Sherlock Breaker
Page 7 of 25
Figure 3.1. SIDAC V-I Characteristics
Each transmitter emits pulses every second that can be detected by the receiver. The power from the electrical
outlet is used to power the transmitter. Each transmitter emits pulses on the positive and negative cycle of the
wave. This is possible because the SIDAC is a bidirectional component placed at the output of two timing
circuits. The timing circuit controls the number of pulses the SIDAC emits in a given time frame. Figure 3.2
shows the transmitter configuration.
Power
Sherlock Breaker is designed to operate with common household circuits. The transmitter operates on the 120V
AC signal coming from the outlet into which it is plugged and distributes it to two parallel diode and RC
networks. The 120V signal goes through a general purpose rectifying diode and is then sent through an RC
network used to control the SIDAC. The diode had to be capable of operating at high voltages without blowing,
so the maximum line voltage of 170V was considered. The diode capabilities limited the selection to a
component that could operate with a peak repetitive reverse voltage of 200V or greater. For safety purposes, a
diode with a peak reverse voltage of 400V was chosen. The forward voltage of the diode is 1.1V, which was
sufficient for the RC network and SIDAC to operate [6]. The transmitter power configuration is shown in Figure
3.3.
Sherlock Breaker
Page 8 of 25
Figure 3.2. Transmitter configuration
120
VRMS
RC Timing
Circuit
SIDAC
Power
Indication
Circuit
Figure 3.3. Transmitter Power Configuration
Timing Circuit
The timing circuit consists of a resistor and capacitor in parallel. Pspice simulations were helpful in choosing
resistor and capacitor values. After looking at an older Sperry Circuit Breaker Finder patent, the older technology
utilized by the Sperry was chosen as a basis for the Sherlock Breaker transmitter. In the Sperry design, only one
size capacitor was used, so the same concept was used for the Sherlock Breaker design [7]. One capacitor is used
with various resistor sizes to create each transmitter. Using one size capacitor makes the design less complex and
costly. Once a capacitor size of 0.47 µF was chosen, the resistor values were calculated to cause the SIDAC to
fire at specific points on the 60Hz sine wave coming from the 120V AC signal.
In order to keep pulses from overlapping, each transmitter must emit a different number of pulses per time frame.
The number of pulses per time frame was decided for each transmitter, and then Pspice simulations were used to
calculate resistor values. The resistor values chosen allow for the SIDAC to emit a signal on positive and
negative wave cycles. To emit 120 pulses per second, which is one pulse on each peak of the 60Hz wave, a
12k Ω resistor was chosen. Figure 3.4 shows the impulses each transmitter emits in relation to the 60Hz sine
wave.
Sherlock Breaker
Page 9 of 25
Figure 3.4. Transmitter Outputs in Relation to a 60Hz sine wave
Indication Circuit
The indication circuit consists of a diode, LED, and resistor in series with the 120V line. The LED is simply for
the user’s benefit. The LED glows as long as the transmitter is receiving power from the 120V line. Once the
breaker to the circuit has been opened, the transmitter loses power and the LED no longer glows as an indication
that power to the circuit has been switched off.
Safety
In order to meet UL Standard 5C91 as the Sperry model meets the standard, a fuse is placed in the transmitter for
user protection. The Underwriters Laboratories Standard 5C91 is a scope for “Surface Raceways, and Fittings for
Use with Data, Signal, and Control Circuits”. According to the scope, the “requirements cover standard raceways
and fittings for Class 2 data, signal, and control circuits”. Mechanical protection and circuit routing are the main
intentions of the raceway systems. These systems do not include applications in accordance with the National
Electric Code, NFPA 70. Requirements for Class 1 circuits are not covered by the scope. It also does not cover
connectors, conductors, cable trays, wire ways, or metal or nonmetallic raceways [8]. The fuse is rated at 1 Amp.
Placement of the fuse can be seen in Figure 3.1.
3.2.2
RECEIVER
Power Supply
Sherlock Breaker is designed to operate with common household circuits. The transmitter operates on the 120V
AC signal coming from the outlet into which it is plugged. A restriction of two AA batteries for the power supply
determined the need for a boost converter to provide the necessary voltage to power the operational amplifier, the
Schmitt trigger, and the microcontroller. A boost converter that sources a large current was needed to power the
peak detector because a capacitor must be charged quickly. The capacitor must be charged quickly because the
transmitter emits a pulse with an extremely short duration of two microseconds.
The operational amplifier is biased at zero volts at the negative rail and five volts at the upper rail, but it is
receiving both positive and negative pulses; therefore, the input signal must come in on top of the center at 2.5
volts [9]. The peak detector requires five volts because it must be capable of holding the output voltage of the
operational amplifier which varies between zero and five volts. The Schmitt trigger supply voltage can vary
between two and six volts [10]. The Schmitt trigger is connected to the boost converter to simplify the circuit.
The microcontroller requires at least 2.2 volts to operate in the defined temperature range; therefore, the
microcontroller is connected to the boost converter [11]. Figure 3.5 shows the DC power configuration.
Sherlock Breaker
Page 10 of 25
DC-DC
Converter
5V
1.5V
1.5V
Voltage
Reference
2.5V
Peak
Detector
Pick-Up Coil
Schmitt
Trigger
PIC
Wiper Terminal
Terminal
Wiper
Digital Pot
+/- Inputs
Op-Amp
Figure 3.5. DC Power Configuration
Pick-up Coil
In order to detect the identifying signal
placed on the line by the transmitter, a
pick-up coil was required. The pick-up
coil was placed between the 2.5-volt
reference and the operational amplifier in
the initial configuration. Problems with
oscillations on the output of the
operational amplifier created the need for
an emitter follower between the reference
voltage and the operational amplifier,
which is the current configuration. A
capacitor is used on the input to filter the
DC voltage. The pick-up coil circuit is
shown in Figure 3.6.
Figure 3.6. Pick-up Coil Configuration
Amplification circuit
The output signal of the operational amplifier needs to follow the input closely. The input pulse has a width of
two microseconds and it is necessary to achieve the maximum value at the output. The operational amplifier was
chosen so that it had a higher slew rate than the calculated value. An example of slew rate is shown in Figure 3.7.
Sherlock Breaker
Page 11 of 25
Figure 3.7. Slew Rate. Courtesy of www.interfacebus.com [12]
VOH is the peak output voltage and VOL is the minimum output voltage, and trise is the rise time of the pulse. The
equation for the slew rate is given as Equation (1) [13].
SlewRate =
(VOH − VOL )* 0.8 = (5V − 0V )* 0.8 = 4V / µs
t rise
1µs
(1)
In the design process, an operational amplifier that had a slew rate of 6V/ µs was chosen. The output of the
operational amplifier needed to swing over a large range of voltages in order for the peak detector and Schmitt
trigger to function properly. The operational amplifier chosen swings rail to rail, which is zero volts to five volts.
The operational amplifier is used in noninverting configuration. The output voltage is calculated using Equation
(2) [14].
⎛ R ⎞
vo = ⎜⎜1 + 2 ⎟⎟vin (2)
⎝ R1 ⎠
The input signal to the operational amplifier varies as the pick-up coil is moved across the breakers. When the
input level is at its highest level, the operational amplifier will be in saturation; however, the design requires that
the peak voltage of the output be measured precisely. A potentiometer is used to adjust the voltage to a point just
below saturation, which is approximately 4.5 volts. The design also requires that the calibration be performed
automatically. For this reason, a digital potentiometer is employed. The digital potentiometer is used as the
feedback resistor in the negative feedback loop of a standard, non-inverting operational amplifier configuration.
The microprocessor controls the gain of the circuit by reading the output of the peak detector and reducing the
gain if operational amplifier is in saturation. The amplification circuit is shown in Figure 3.8.
Peak Detector
The peak detector is used to detect the voltage level at the output of the operational amplifier. The
microprocessor monitors this voltage level using an A/D converter and adjusts the digital potentiometer
accordingly. The original peak detector consisted of a Schottky diode in series with a capacitor and resistor
combination. Theoretically, this design allowed the positive peak amplitudes to be maintained across the
combination. However, the operational amplifier was not capable of sourcing enough current to charge the
capacitor during the pulse. To correct this problem, a low saturation transistor was used as shown in Figure 3.9.
Sherlock Breaker
Page 12 of 25
Figure 3.8. Amplification Circuit Configuration
Figure 3.9. Peak Detector Configuration
Originally, the peak detector was not capable of receiving the amount of current necessary to hold the maximum
voltage. This configuration solved that problem, but the DC-DC converter could not supply an adequate current
level. To solve this problem, a larger capacitor was placed from the DC-DC converter output to ground.
Multivibrator
In order for the microprocessor to count the number of pulses at its input, a +5V signal of at least 10
microseconds in length is necessary. A multivibrator in the form of a Schmitt trigger is used to accomplish this
task. During normal operation, the positive or negative output of the operational amplifier will appear at the input
to the Schmitt trigger when a positive or negative pulse, respectively, appears at the pick-up coil. Each time the
Schmitt trigger receives a pulse, whether positive or negative, it outputs a positive 5-volt signal that is 10
microseconds long. The microprocessor easily counts the number of pulses over a specific time frame using this
configuration.
Sherlock Breaker
3.3
Page 13 of 25
SOFTWARE DESIGN
Overview
The Sherlock Breaker receiver contains the software portion of the project. A physical model indicating the
externally controlled settings on the receiver is show in Figure 3.10.
Switch to determine which transmitter to find
Button to hold during calibration
Figure 3.10. Receiver Physical Model
The receiver contains a pick-up coil that detects the pulses the transmitters send over the line. The pick-up coil
then sends the signal to the operational amplifier, which then sends a signal to the multivibrator and the peak
detector. The multivibrator emits a 5-volt, 10 microsecond signal to the microprocessor to be counted and to
identify the transmitter or transmitters that are detected. The peak detector detects the voltage level at the output
of the operational amplifier, and then sends a signal to the microprocessor, or PIC, which converts the analog
signal to a digital signal. The digital signal adjusts the digital potentiometer and sends the signal back to the
operational amplifier. The PIC then sends a signal to the LED and buzzer when the counted signal matches the
pulses per second count for the selected transmitter. The receiver configuration is shown in Figure 3.11.
M u ltiv ib ra to r
P ic k -U p C o il
P IC
O pam p
Peak
D e te c to r
D ig ita l
P o te n tio m e te r
Figure 3.11. Receiver Configuration
LED /
B uzzer
Sherlock Breaker
Page 14 of 25
Microprocessor
Originally, the circuit breaker finder design contained all discrete components. This design was effective, but had
manual sensitivity controls. After studying the design of the Sperry and other circuit breaker finders, the group
members decided that automatic calibration would be an added feature for the Sherlock Breaker. In order to have
automatic calibration, a PIC was needed. The PIC, peripheral interface controller, is a microprocessor that can
auto calibrate the digital potentiometer by taking in an analog signal from the multivibrator and output a digital
signal to the digital potentiometer.
Several microprocessors are capable of analog to digital conversion, but the cheapest version at the time was
chosen because of the basic needs. This microprocessor chosen to be included in the Sherlock Breaker receiver is
the PIC12F675 [15]. Several tasks were added to the PIC to make the receiver more efficient. These tasks
include lighting a light emitting diode for user indication, measuring a time interval in which to count pulses,
counting pulses emitted by the transmitters, and for processing the inputs and outputs. The second-hand timer can
handle up to a 40MHz pulse, which is equal to 2 microseconds [15]. Initialization of the microprocessor, pin
settings and timer settings, were edited from samples in Easy Pic'N: A Beginners Guide to Using Pic16/17
Microcontrollers from Square 1 [16]. Pin inputs and outputs are programmed according to the pin layout in the
Memory Programming Specification [17].
3.3.1
Calibration Circuit
The calibration circuit uses the analog to digital converter of the PIC. First, the PIC measures the amplitude of
the analog signal output from the operational amplifier, then converts the signal to a digital signal and sends it to
the digital potentiometer to adjust the potentiometer accordingly. The PIC will interface with the digital
potentiometer using SPI, or Serial Peripheral Interface. The digital potentiometer will begin at the maximum
resistance and reduce the resistance in increments until the output of the operational amplifier is not too high for
the peak detector to read. Beginning with the maximum resistance and reducing the resistance will ensure that the
circuit is never overloaded. The iterations of the calibration circuit are shown in Figure 3.12.
Select
Transmitter
A, B, or C
Calibrate
or Read
Calibrate
Read Signal
Level
Adjust Digital
Potentiometer
Read
To Pulse
Counting
Is Vout
too
High?
YES
NO
Figure 3.12. Diagram of the Calibration Circuit
Sherlock Breaker
Page 15 of 25
User
Transmitter/
Receiver
Receiver set to “Off”
User plugs Transmitters B and C into different wall outlets
User returns to breaker box and sets Receiver to “A”
“No Signal Found” LED blinks continuously
User presses and holds Calibrate button while moving the Receiver over each circuit breaker
User releases Calibrate button after moving the Receiver over each circuit breaker
“No Signal Found” LED stops blinking, but LED remains on
User moves Receiver over each breaker, pausing ½ second over each circuit breaker
"No Signal Found" LED remains on as User scans entire breaker box
User sets Receiver to “Off”
Figure 3.13. Use Case for a Typical Breaker Box Reading
3.3.2
Counting Circuit
The counting circuit has two timers. The first timer is used to delay 1/10 of a second. The second timer is set as
an external clock and will increment the timer register for every high pulse from the Schmitt trigger. After 1/10
of a second, the clocks are stopped and the total number of pulses is read from the second timer. This value is
calculated against known values of combinations of signals from the transmitter frequencies. If the number of
signals matches a known value, the LED will flash once if the first transmitter is detected, twice if the second
transmitter is detected, and three times if the third transmitter is detected. If two pulses are found on the circuit,
the LED will flash the given number of times for one signal, pause, and then flash the given number of times for
the other signal. If all three transmitter signals are found, the LED will flash the given number of times for one
signal, pause, flash for the next signal, pause, and then flash for the last signal. The timer then resets, and the
process is repeated. The use case for a typical breaker box reading is shown in Figure 3.13. A diagram of the
logic for the counting circuit is shown in Figure 3.14.
Sherlock Breaker
Page 16 of 25
F ro m
C a lib ra tio n
Is P u ls e
Found?
YES
R e a d P u ls e
fro m
M u litv ib ra to r
NO
L ig h t
“N o S ig n a l”
LED
C ount
P u ls e s
NO
D oes
C ount
M a tc h ?
YES
L ig h t
“S ig n a l”
LED
Figure 3.14. Diagram of Counting Circuit
A detailed, graphical summary of how the receiver components interact is shown in Figure 3.15 on the following
page.
Sherlock Breaker
Page 17 of 25
DC-DC boost
Convert the 3V of the batteries to 5V for
the PIC
Inductive Probe
Detects electro-magnetic field generated
on the circuit by the transmitter(s)
Digital Potentiometer
Calibration: Set to the appropriate
resistance by the PIC so that the op-amp
amplifies the signal to easily be detected
by the Schmitt trigger and the PIC
Counting: Resistance value remains
constant
Op-amp
Calibration: Boosts input signal based
on the digital resistor value set by the
PIC
Counting: Boosts the input signal for
the Schmitt trigger
PIC
Calibration:
Determines strength of incoming signal and
adjusts the digital potentiometer accordingly
Counts the incoming pulses to adjust the
amplitude for the selected transmitter
Alerts the user when calibration is required
by flashing the “No Signal Found” LED
Counting:
Counts the pulses sent by the Schmitt trigger
Determines if the correct transmitter is on
the current circuit breaker from the number
of pulses counted
Alert the user that the signal for a
transmitter was found by illuminating the
proper LED
LEDs
Alert the user about the “receiver status”
No signal
Calibration needed
Signal found
Multivibrator
(Schmitt Trigger)
Convert the pulses from the op-amp
signal to clean pulses to be counted by
the PIC
Figure 3.15. Receiver Overview Diagram
4.
EVALUATION
This section contains two major sections, Test Specifications and Test Certifications
4.1
Test Specifications
Sherlock Breaker will be broken down into two separate components, the receiver and the transmitter. Each
component will be constructed and tested individually. Before each component is built, simulations in software
will be conducted to ensure desired functionality. Once each component is simulated, it will be built, and then
tested for actual functionality. After each part has passed the functionality test, the parts will be integrated into
the system for final simulation and testing. The testing methods are summarized in Table 4.1.
Sherlock Breaker
Constraints
Page 18 of 25
Pspice
MPLAB, IDE
Oscilloscope
Digital Multimeter
Transmitter
Input Voltage
Transmitter
Output Voltage
Transmitter
Current Peaks
SIDAC
Output Voltage
SIDAC
Output Current
Receiver Input
Voltage
PIC
Inputs
PIC
Outputs
Prototype
Components
Table 4.1. Testing Methods for Sherlock Breaker
4.2
Test Certification – Simulation
Pspice
Pspice, a circuit simulation software tool, will be used to simulate the transmitter. When evaluating circuits in
Pspice, theoretical output values are generated. Actual values will come from hardware testing as the prototype is
built.
MPLAB, IDE
MPLAB, IDE is a software interface that allows a user to compile programs specifically written for a PIC
microcontroller. The compiler allows the PIC to be programmed and erased using the interface. The assembly
language code can be stepped through to ensure proper functionality. MPLAB, IDE supports flash memory.
4.2.1
Transmitter
For the transmitter, a resistor and a capacitor are placed in parallel to determine the value of the time constant. A
standard 0.47-microFarad capacitor can be chosen as a base and the resistor value can be changed for each of the
three transmitters. Several base resistor values were chosen to begin simulations. Changing the resistor value
results in an evenly spaced pulse “placement” change along the 60-Hertz sine wave. Pspice will be used to
simulate the voltage and pulse changes as the resistor value changes and as a guide to choosing the resistor values
that will be used in the prototype. The Pspice outputs will be compared to mathematical calculations to determine
whether or not the values are acceptable.
4.2.2
Receiver
Matlab, Simulink, and MPLAB, IDE will be used to simulate the receiver. Matlab and Simulink will be used to
simulate frequencies and pulses that the PIC will receive. The theoretical values produced by Matlab and
Simulink will be used as the comparison basis for the actual frequencies and pulses. Any changes to the hardware
will be simulated in Matlab and Simulink for further comparison. MPLAB, IDE will be used to step through
Sherlock Breaker
Page 19 of 25
the PIC code line by line. The program allows the user to view the current status of all input and output ports and
works for a majority of PIC-18 chips. The user can also view output changes as a result of input adjustments
inside the code. The output values will be compared to anticipated outcomes to determine whether or not the
outputs are acceptable.
4.3
Test Certification – Hardware
Physical Testing
The transmitter and receiver will be tested simultaneously with a breaker box. The transmitter will be plugged
into a wall outlet or receptacle and the receiver will be used to match the wall outlet circuit to the correct breaker.
The transmitter and receiver will be tested multiple times with different circuits to determine the accuracy of the
Sherlock Breaker system. Testing setups for individual components are listed below.
4.3.1
Transmitter
The Tektronix TDS-724D Oscilloscope will be used in DPO mode to efficiently monitor the pulses output
by each SIDAC. A regular breadboard with ½-Watt resistors and 400-volt capacitors will be used as a prototype
for the transmitter. A small resistance will be placed in series with the transmitter in order to scale the 120-volt
input voltage to an acceptable level that can be read by the oscilloscope. Measurements taken by the oscilloscope
can be saved and exported to a Microsoft Excel file for graphical representation. The primary function of the
oscilloscope is to test voltage, current, and frequency. Power and efficiency can be calculated using the current
and voltage measurements. The digital multimeter will be used to verify resistances and capacitances. The test
setup is shown in Figure 4.1.
Figure 4.1. Transmitter Test Setup
4.3.2
Receiver
The Tektronix TDS-724D will also be used to monitor the output of the receiver as the inductive probe is passed
in close proximity of the transmitter. The output of the oscilloscope can be saved, exported to a Microsoft Excel
file and graphically represented as with the transmitter. The digital multimeter will be used to verify resistances
and capacitances integrated into the circuit design. Additionally, a Circuitmate Function Generator FG2 will be
used to generate a signal to the Schmitt trigger.
4.3.2.1 Boost Circuit
The boost circuit will be tested by measuring the input and output voltage of the DC-DC boost circuit with a
digital multimeter. A digital multimeter will also be used to measure the voltage across a 2.5V reference. Figure
4.2 shows the test setup for the boost circuit.
Sherlock Breaker
Page 20 of 25
Figure 4.2. Boost Circuit Test Setup
4.3.2.2 Amplification Circuit
The amplification circuit will be tested by sending very small pulses from the pulse generator to the op-amp. The
potentiometer will be used to adjust the amplification level from 0V to the upper rail voltage. The oscilloscope
will used to verify that the amplification level is changing. Figure 4.3 shows the test setup for the amplification
circuit.
Figure 4.3. Amplification Circuit Test Setup
4.3.2.3 Peak Detector
The pulse generator will send pulses to the peak detector to simulate the output of the op-amp at approximately
4.5V. The oscilloscope will measure the voltage across the peak detector. Figure 4.4 shows the test setup for the
peak detector.
Figure 4.4. Peak Detector Test Setup
4.3.2.4 Multivibrator
The pulse generator will be used to send 4.5V pulses to the multivibrator. The oscilloscope will check to see if
the output of the multivibrator is a 5V pulse of 10microsecond duration. Figure 4.5 shows the test setup for the
multivibrator.
Figure 4.5. Multivibrator Test Setup
Sherlock Breaker
Page 21 of 25
4.3.2.5 Calibration Circuit
The calibration circuit will be used to set the input voltage of the Schmitt trigger. The voltage source will
represent the peak detector, which will be monitored by the PIC. The PIC will then send a signal to the digital
potentiometer to adjust the resistance, thus adjusting the voltage. A digital multimeter will be used to verify that
the resistance of the digital potentiometer is adjusted correctly. Figure 4.6 shows the test setup for the calibration
circuit.
Voltage
Source
PIC A/D
Converter
Digital
Potentiometer
Digital Multimeter
(Ω )
Figure 4.6. Calibration Circuit Test Setup
4.3.2.6 Counting Circuit
The pulse generator will be used to input different number of pulses to mimic the potential pulses that will be put
on the line by the three transmitters. The PIC will then sum the number of pulses for a given time (0.1 seconds)
and compare to the shared values to determine which transmitters are on the circuit. The PIC then turns on the
LED’s to signify the transmitters. If “A” is found on the line by itself or in a combination with “B”, “C”, or “B”
and “C,” then the “A” LED will be lit. As the frequency or number of pulses changes, the LED will be turned off
until the pulses are again counted and appropriately lit. Figure 4.7 shows the test setup for the counting circuit.
PIC
Pulse
Generator
LED
LED
LED
A
B
C
Figure 4.7. Counting Circuit Test Setup
4.4
Test Certification – Software
4.4.1
Transmitter
The transmitter will not have any software.
4.4.2
Receiver
Simulink and MPLAB, IDE will be used to test the majority of the software. Software testing of the prototype
will ensure that the LEDs and input switches are functioning properly. Simulink will be used to generate an input
signal. MPLAB, IDE will be used to simulate the assembly language program that will control the functions of
the receiver. Inputs in the program code can be changed and the outputs can be monitored to evaluate the effects
of input changes. MPLAB, IDE will be used to step through each line of code and check register values. The
register values will be compared to anticipated values to determine whether or not the register values are accurate.
The SPI interface between the digital potentiometer and the PIC will be tested by checking the register values and
the PIC inputs. Once the register values are verified, the software testing will be complete.
Sherlock Breaker
5.
Page 22 of 25
SUMMARY AND FUTURE WORK
Figure 5.1 summarizes which constraints were fully met, partially met, and not met or untested.
Constraint
Met
Applicable Line Voltages: 120V
Transmitter Signal: 20A at no more than 3 microseconds
Environment (power) 2 AA batteries
Economical: Packaged for less than $80
Manufacturability (size): Wait until SD II
Multiple Transmitters: Distinguish up to 3 different transmitters
Applicable Line Length: Accurate up to 300 feet
Safety: Use applicable fuses for UL Standards
Signal Strength Calibration: Automatic calibration
X
X
X
X
Reliability (accuracy and maintenance):
Testing in a variety of locations
Partially
Met
Not Met /
Untested
X
X
X
X
X
X
Figure 5.1 Design Constraint Summary
Several constraints were completely met. The transmitter prototype successfully operated for 120V wall outlets.
The transmitter emitted a signal within the time allotted. The receiver was powered using only 2 AA batteries.
The entire Sherlock Breaker package, three transmitters and one receiver, are expected to sell for less than 80
dollars.
Two constraints were partially met. Although all the components for the receiver and transmitter fit within size
requirements, the group opted to wait until Senior Design II before claiming to meet this constraint. The
prototype can distinguish three transmitters individually, but only two transmitters could operate simultaneously.
Sherlock Breaker recognizes each of three transmitters when operated individually. The prototype is able to
distinguish the 120 pulses-per-second transmitter from the 60 pulses-per-second transmitter when they operate
simultaneously. The group plans to work with the 40 pulses-per-second transmitter to coordinate the resistance
value that will allow it to be recognized simultaneously with the other transmitters.
Several constraints were not met or untested. The prototype was not tested on a circuit of length 300 feet. The
prototype was not tested in as large a variety of locations as planned, such as homes of various sizes. However,
the transmitter and receiver worked properly on the test set-up built by the group. The transmitter was not built
with an applicable UL-standard fuse. Although the peak detector was designed, it was not fully integrated into
the receiver system. Therefore, the receiver did not have automatic calibration capabilities at the end of Senior
Design I.
Several major and minor additions can be made to Sherlock Breaker in Senior Design II. The two largest
additions are having a properly working third simultaneous transmitter and an automatically calibrating receiver.
The Sherlock Breaker team intends to add a switch to the prototype so that only one transmitter can be searched
for at a given time. Also, an automatic calibration circuit will be added to help discern each transmitter from the
other. This automatic calibration circuit will adjust a digital potentiometer using the microprocessor. The
recognition of each transmitter is done by counting pulses on the line. A better way to discern the transmitters is
to use a Fourier transform. This would allow for transmitters to be distinguished even on an extremely noisy line.
Minor additions include possibly having a light bulb adapter for a transmitter and an automatic power-off feature.
Sherlock Breaker
6.
Page 23 of 25
ACKNOWLEDGEMENTS
The Sherlock Breaker group wishes to thank our faculty advisor, Dr. Noel Schulz, for her patience and
suggestions during our first semester of design work. Dr. Lori Bruce and Dr. Herb Ginn also provided helpful
design ideas for the transmitter. Dr. Raymond Winton helped with PSpice difficulties. Jean Mohommadi-Aragh,
Joel Martin, and Odie McHann also assisted the group throughout the project life.
7.
REFERENCES
1. Mary Bellis, “The Inventions of Thomas Edison,” 14 Sept 04. [Online]. Available:
http://inventors.about.com/library/inventors/bledison.htm
2. Wavetek Meterman Tools, “Circuit Breaker Finder,” 24 Aug 2004. [Online]. Available:
http://www.industrialnewsroom.com/fullstory/29932.
3. Professional Equipment, “Greenlee® Circuit Breaker Finder,” 24 Aug 2004. [Online]. Available:
http://www.professionalequipment.com/xq/ASP/ProductID.1562/id.5/qx/default.htm
4. Wavetek Meterman Test Tools, “New Tool from Wavetek Meterman® Traces Circuits for 500 Feet,” 8
Aug 2004 [Online]. Available: http://www.industrialnewsroom.com/fullstory/29932
5. Tony R. Kuphaldt, “The Shockley Diode,” in Lessons in Electric Circuits, Volume III-Semiconductors,
[Online Book]. 6 Nov 2004. Available: http://www.allaboutcircuits.com/vol_3/chpt_7/3.html
6. Fairchild Semiconductor Corporation, “1N4001-1N4007 General Purpose Rectifiers,” Datasheet
Document. Cat. No. 1N4004. 2003.
7. John G. Konopka, “Power Circuit Locator,” United States Patent, 4,906,938,6March 1990.
8. Underwriters Laboratories, “Surface Raceways and Fittings for Use with Data, Signal, and Control
Circuits,” 6 Nov 2004. [Online Documentation]. Available:
http://ulstandardsinfonet.ul.com/scopes/0005C.html
9. Burr-Brown Corporation, “OPA340, OPA2340, OPA4340 Single-Supply, Rail-To-Rail Operational
Amplifiers,” Datasheet Document. Cat. No. OPA340. December 1997.
10. Toshiba, “TC74HC123AP, TC74HC123AF, TC74HC123AFN, Dual Retriggerable Monostable
Multivibrator,” Datasheet Document. Cat. No. TC74HC123AP. August 7, 1997.
11. Microchip Technology Inc., “MCP1525/1541 2.5V and 4.096V Voltage References,” Datasheet
Document. Cat. No. MCP1525. 2001.
12. Leroy Davis, “Logic Family Slew Rate,” 5 Nov 2004. [Online]. Available:
http://www.interfacebus.com/IC_Output_Slew_Rate.html
13. Donald A. Neaman, “Slew Rate,” in Electronic Circuit Analysis and Design, St. Louis: McGraw Hill,
2001, pp.888-892.
14. James W. Nilsson and Susan A. Riedel, “The Noninverting Amplifier Circuit,” in Electric Circuits, 6th
ed., New Jersey: Prentice Hall, 2001, pp. 199.
15. Microchip Technology, Inc., “PIC12F629/675 8-Pin FLASH-Based 8-Bit CMOS Microcontrollers,”
Datasheet Document. Cat No. PIC12F675. 2003.
Sherlock Breaker
Page 24 of 25
16. David Benson, Easy Pic'N: A Beginners Guide to Using Pic16/17 Microcontrollers from Square 1, 3.1
ed., Idaho: Square One Electronics, 1996.
17. Microchip Technology, Inc., “PIC12F629/75/PIC16F630/76 Memory Programming Specification,”
Datasheet Document. Cat No. PIC12F675.2004.
Sherlock Breaker
Page 25 of 25
APPENDIX A: PRODUCT SPECIFICATION
SHERLOCK BREAKER
Sherlock Breaker (SB) is a multiple-piece device that allows an individual to determine which circuit breaker
controls a specific 120-volt AC electrical receptacle such as a wall outlet. SB is designed to work without
requiring the user to switch off power to other appliances on the same circuit. SB allows multiple transmitters to
connect to the same circuit, ensuring connectivity between outlets in the same vicinity.
Primary Applications
•
•
Installing or changing an electrical outlet
Other electrical jobs requiring circuit power to be
switched off
•
•
Locate breakers quickly and with only one person
Other electrical devices on the same circuit remain
turned on and unaffected
Ideal for residential locations—works on both indoor
and outdoor outlets!
Lifetime warranty protects your SB investment!
•
•
Sherlock Breaker Advantages
Technical Information
Transmitter
Properties
Receiver
Properties
Operating
Temperature
Circuit
Length
Limitations
Water
Resistance
Product
Certifications
Additional
Features
4 X 3 X 2 (in ³); 10 ounces;
120 VAC with a 2-prong
plug;
Uses a SIDAC to generate
pulse signals
8 X 2.5 X 1.5 (in ³); 15
ounces;
Requires 3 volts using 2 AA
batteries; Uses a PIC for
signal discrimination
32° F to 140° F
Accurate for circuits up to
300 feet long
Water-resistant; not
waterproof
UL, FCC
Visual indicators
Lifetime warranty120
Sherlock Breaker
Product Usage
The user plugs the SB Transmitter into a
wall outlet of the circuit to be labeled. At
the circuit breaker box, the user scans each
breaker one at a time with the SB
Receiver. When the SB Receiver finds the
correct breaker, an audible alarm and LED
alert the user that a connection has been
found.