Power Supply Project
by
Robert Lockhart
(100529503)
Course Code: CAD 1133
Course Name: CAD for Electronics I
Date: April 16th, 2014
Submitted to: Professor D. Grenier
1
Abstract
The purpose of this project was to create a PCB board from scratch using a program called
Eagle. There are many steps in completing the final PCB. The PCB takes alternating
current from a centre tapped transformer and outputs three direct current regulated
voltages, including a fixed 5V, +(0-15)V variable and a dual tracking –(0-15V).
The first step was to create a schematic using a program called Mulitisim. Multisim is a
simulation program that helps you create circuits and simulate them to help guide you and
help you understand how the circuit works.
Upon completion of the Multisim simulation, several labs were completed to simulate the
different parts of the circuit on the PCB. Eagle was then also used to create a schematic.
The professor provided a template schematic with several parts missing; our goal was to
solve for what components had to go where. When this was completed the schematic could
finally be put together. From the schematic created on Eagle, a circuit board could then be
created. Much work was put in to routing the circuit on the PCB. The components go on
top of the board and the traces on the bottom.
When the completion of the PCB was done, a process using GS view was used to create
the actual template which was transferred onto a transparency. The transparency was just
a negative view of the trace son the bottom. The transparency was then taken to the lab.
Through a chemical process, the circuit board was completed.
When the circuit board was completed it was then time to solder all the components onto
the board. From there the board was then mounted into the provided box and the final
connections were made so that the box would function and display the correct voltage
outputs.
2
Acknowledgements
Thank you Pravin Patel for teaching me the lecture part of the course which helped guide
me to understand how every part of the circuit functioned. I would like to thank Denis
Grenier for the support and guidance throughout the entire project. I would also like to
thank Dave MacKay for his help and guidance in the LAB. Without any of these people
this project would not have been possible.
3
Contents
Title Page ............................................................................................................................1
Abstract ...............................................................................................................................2
Acknowledgement...............................................................................................................3
Contents............................................................................................................................4-5
List of Figures......................................................................................................................6
Section I...............................................................................................................................7
The Power Supply Project
Aims of the Project
Section II...........................................................................................................................8-9
Project Schematic and Circuit Operation
Schematic Drawing
Operation of the Power Supply......................................................................................9-10
Power Rectification
AC-DC Rectification....................................................................................................10-11
Fixed 5 V Power Supply...............................................................................................12-13
0-15 V Variable Power Supply.....................................................................................14-15
Negative 0-15 V Variable Tracking Power Supply……………………………….….16-17
Section III...........................................................................................................................18
Printed Circuit Board
Eagle CAD Schematic
Printed Circuit Board Layout.......................................................................................19-20
Printed Circuit Board Production.................................................................................21-22
Section IV………………………………………………………………………………..23
Power Supply Box
Box Drawing
Box
Production………………………………………………...………….……...………..24-25
4
Section V………………………………………………………………………..26-27-28
Finally Assembly and Testing
Assembly
Testing
Section VI.....................................................................................................................29-30
Summary and Conclusions
Schematic Drawing
Printed Circuit Board Drawing
Printed Circuit Board Production
Box Drawing
Box Production
Assembly and Testing
Conclusions
5
List of Figures
Figure 1 Initial Schematic....................................................................................................8
Figure 2 Final Schematic.....................................................................................................9
Figure 3 Power Rectification.............................................................................................10
Figure 4 AC-DC Rectification
Figure 5 AC-DC Rectification (Oscilloscope)...................................................................11
Figure 6 AC-DC Rectification (Oscilloscope)...................................................................12
Figure 7 Multimeter Reading
Figure 8 Fixed 5 Volts.......................................................................................................13
Figure 9 0-15 Variable Power Supply with Potentiometer at 100%..................................14
Figure 10 Multimeter reading at 100%
Figure 11 0-15 Variable Power Supply with Potentiometer at 0%....................................15
Figure 12 Multimeter reading at 0%
Figure 13 Negative 0-15 V Variable Power Supply with Potentiometer at 100%............16
Figure 14 Multimeter reading at 100%..............................................................................17
Figure 15 Eagle CAD Schematic.......................................................................................18
Figure 16 Eagle Board (routes)..........................................................................................19
Figure 17 Eagle Board (copper pour)................................................................................20
Figure 18 Box Drawing.....................................................................................................23
6
Section I
Introduction and Purpose
The Power Supply Project
The purpose of this project was to create a PCB board from scratch using a program called
Eagle. There are many steps in completing the final PCB. The PCB takes alternating current
from a centre tapped transformer and outputs three direct current regulated voltages, including
a fixed 5V, +(0-15)V variable and a dual tracking –(0-15V).
Aims of the Project
It is therefore the main aims of the project are:
(a)
Complete a schematic and design a circuit board using Eagle,
(b)
Construct the circuit board on Eagle, use the Lab to physically complete the
board, and
(c)
Construct a box to function as a 0-15 V positive and negative as well as a fixed
5V.
7
Section II
Project Schematic and Circuit Operation
A schematic is one of the most important necessities of every electronic circuit. The purpose
of the schematic is to display; to the reader; how all the connections are made, and where/how
the components are placed and laid out.
Schematic Drawing
Figure 1 was the incomplete schematic we were provided. We were given the task to
complete the schematic through our knowledge of circuits.
µ
µ
µ
µ
µ
Figure 1 Initial Schematic
8
Figure 2 shows the completed schematic. Through our knowledge we could determine how the
circuit should be completed. Through calculations we were able to determine what size
component and what component had to be located where.
Figure 2 Final Schematic
Operation of the Power Supply
Power Rectification
The AC input voltage is changed to DC voltage. The diodes clip the waveform making only a
positive or negative wave. The capacitors are used to smooth the waveform. Figure 3 shows
the power rectification section of the Eagle schematic.
9
Figure 3 Power Rectification
AC-DC Rectification
Figure 4 displays the rectification. AC is the reading at the secondary of the transformer. DC
is the reading from common (ground) to the first diode which is filtered by the capacitors.
DC
AC
Figure 4 AC-DC Rectification
10
Figure 5 displays the circuit from which the oscilloscope readings were taken.
XSC1
U1
LM117HVH
Ext Trig
+
Vin
Vout
_
+
ADJ
B
A
_
+
_
R4
120Ω
S2
Key = Space
F1
0.5_AMP
S1
Key = Space
D1
1N4007GP
D2
1N4007GP
C3
10µF
D8
1N4007GP
R1
C1
2.2mF
100Ω
100%
Key=A
T1
V1
120 Vrms
60 Hz
0°
4.1
115/28 Vac 28VA
D6
1N4007GP
D3
1N4007GP
D4
1N4007GP
C2
2.2mF
D7
1N4007GP
R3
R2
1kΩ
Figure 5 AC-DC Rectification (Oscilloscope)
11
2kΩ
70%
Key=A
Fixed 5V Power Supply
The 5V supply is one of the three DC supplies in the final project Power Supply. It consists of
two diodes D1 and D2, one electrolytic capacitor, C1, and one LM7805 voltage regulator. The
diodes convert the AC to DC, which is a process called rectification. The capacitor smooths
the large changes in the DC signal as seen in Figure 4.The regulator maintains the voltage
going to the load at 5V.
Figure 6 shows the circuit with a multimeter (XMM4) reading the output voltage of the 7805
regulator.
XMM2
U1
LM7805CT
XMM5
LINE
VOLTAGE
VREG
XMM4
COMMON
XSC1
Ext T rig
+
S2
Key = Space
1
_
+
Space
D1
1N4007GP
B
A
_
+
_
D2
1N4007GP
R1
C1
2.2mF
T1
4.1
115/28 Vac 28VA
Figure 6 AC-DC Rectification (Oscilloscope)
Figure 7 is the reading on the multimeter.
Figure 7 Multimeter reading
12
100Ω
100%
Key=A
Figure 8 displays the smooth line of the fixed 5 volts coming from the 7805 regulator.
Figure 8 Fixed 5 Volts
13
0-15V Variable Power Supply
This supply is a variable supply unlike the 7805 which was a fixed supply. By changing the
position of the slider for the potentiometer, the resulting change in the resistance will cause
the output voltage of the LM317 to change. Figure 9 is the 0-15 V power supply part of the
project.
U1
LM117HVH
XMM5
Vin
Vout
XMM6
ADJ
R4
120Ω
S2
Key = Space
D1
1N4007GP
D2
1N4007GP
C3
10µF
D8
1N4007GP
R1
C1
2.2mF
100Ω
100%
Key=A
D6
1N4007GP
D3
1N4007GP
D4
1N4007GP
C2
2.2mF
D7
1N4007GP
R3
R2
1kΩ
1.5kΩ
100%
Key=A
Figure 9 0-15V Variable Power Supply with potentiometer at 100%
In the position shown in Figure 9, at 1.5KΩ/100%; full resistance, the output voltage is close
to 15V. Figure 10 is the reading on the multimeter (XMM 6) when the potentiometer is at
100%.
Figure 10 Multimeter reading at 100%
14
All the components below the common signal coming out of the centre tap of the transformer
that are on the PCB serve the purpose to allow the regulator to output 0V when the pot is
turned all the way down. In the position shown in Figure 11, at 0Ω/0%; no resistance, the
output voltage is practically 0 V.
XMM2
U1
LM117HVH
XMM5
Vin
Vout
XMM6
ADJ
R4
120Ω
S2
Key = Space
S1
Key = Space
D1
1N4007GP
D2
1N4007GP
C3
10µF
D8
1N4007GP
R1
C1
2.2mF
100Ω
100%
Key=A
T1
4.1
115/28 Vac 28VA
D6
1N4007GP
D3
1N4007GP
D4
1N4007GP
D7
1N4007GP
C2
2.2mF
R3
R2
1kΩ
1.5kΩ
0%
Key=A
Figure 11 0-15V Variable Power Supply with potentiometer at 0%
Figure 12 is the reading on the multimeter (XMM 6) when the potentiometer is at 0%.
Figure 12 Multimeter reading at 0%
15
Negative 0-15V Variable Tracking Power Supply
This supply is a variable supply unlike the 7805 which was a fixed supply. It is very similar to
the postivie 0-15 V variable supply; it just has more components due to the complexity of it.
The larger number of components in the negative circuit compared to the positive circuit is due
to the fact that it automatically tracks the output
of the positive voltage regulator and ensures the
REG2
XMM5
Key = Space
LM117HVH
output of the negative regulator is equal in magnitude. Thus the designation of the power supply
Vin
Vout
ADJ
XMM2
XMM6
as a dual tracking SW2
power supply. By changing theR2position of the slider for the potentiometer,
120Ω
the resulting 1N4007GP
change in the resistance
will cause the output1N4007GP
voltage of theLoad1
LM337 to change.
R5
D1
XMM4
680Ω
D2
D8
C3
10µF project.
Figure 13 is the negative
C1 0-15 V power supply part of the
2.2mF
1N4007GP
R7
10kΩ
100Ω 100%
Key=A
D5
1N5232B
T1
5/28 Vac
VA
D6
1N4007GP
4.1
1N4007GP
D3
D4
C2
2.2mF
5
1
7
D7
1N4007GP
U4
3
6
1N4007GP
R6
10kΩ
2
R4
1kΩ
4
UA741CD
R1
220Ω
R3
3
2kΩ
70%
Key=A
2
REF
VIN VOUT
VREF
1
XMM7
U11
LM337
Figure 13 Negative 0-15V Variable Power Supply with potentiometer
at 100%
16
1N4007GP
C4
D9
10µF
In the position shown in Figure 14, at 2.0KΩ/70%; about 1.5KΩ of resistance, the output
voltage is close to negative 15V. Figure 14 is the reading on the multimeter (XMM 7) when
the potentiometer is at 70%.
Figure 14 Multimeter reading at 100%
The operation of this circuit is more complicated than the other two regulated output circuits. It
works the same as the positive regulated circuit. The resistor R7 works the same as R2 in the
LM317 circuit
Pins 4 and 7 of the Op Amp are the negative and positive power supplies for the Op Amp. The
voltage at pin 4 will be the same as the input to the LM337 regulator which is approximately 20 V. The voltage at pin 7 will be the same as found at the cathode of the zener diode.
In this circuit the Op Amps is used as a comparator. Using the Op Amp as a comparator means
that the input at pins 2 and 3 are constantly being compared and changes here are reflected in the
output. These changes are always the result of a change in voltage at pin 2 since pin 3 is
connected to common and thus will always be at the same potential.
17
Section III
Printed Circuit Board
Using the program Eagle the template for the circuit board was created. Upon completion of
the template of the board, we had to go first created a transparency of the board template. It
was then taken to the lab to create the board. There are many specific details that must be
followed.
Jumpers are used to jump routes that cannot cross, otherwise a short is created.
Eagle CAD Schematic
Figure 15 is the Eagle cad schematic. This was used to create the physical board with all the
routes necessary to complete the board.
Figure 15 Eagle CAD Schematic
18
Printed Circuit Board Layout
Shown in Figure 116 is the complete board created on Eagle from the schematic. Placement of
the components is critical. The one rule that I tried to stick to was attempting to place the
components similar to how they are laid out in the schematic. This makes it much easier to
route them. The route command is used to physically connect the components together with
copper. (This process is highlighted in the Printed Circuit Board Production section.) The red
square is the heat sink which is on the top of the board. The blue lines are cooper, which are
routes; these are located on the bottom of the board. The green squares are to signify where
jumpers must be soldered to connect the copper where a jump was required.
Figure 16 Eagle Board (routes)
Figure 17 displays the “copper pour”. The copper pour is created using a polygon command in
Eagle. This creates the dashed blue line around the board (the area where the copper must be
“poured into”). A command called “ratsnest” creates the “copper pour”. The blue areas are the
ground plane. The ground plane is used to ground all the components that must be connected
19
to ground. The ground plane eliminates almost 30% of the routes, making it much easier to
route.
Figure 17 Eagle Board (copper pour)
20
Printed Circuit Board Production
Step 1: Acquiring Transparency
The first part of preparing to enter the lab was to acquire a transparency with the negative
image of the board traces.
Step 2: Image Transfer to PCB from Digital Device
With the acquired transparency you had to enter the lab and go to the UV box. The negative of
the board was flipped over onto the centre of the glass surface of the UV box. It was then closed
and the light started. Where the UV light shone through the negative was where the photo-sense
material was hardened onto the PCB. This is where to copper will end up. Where the light did not
hit was where the photo-sense material remained soft.
Step 3: Photo Developer Machine
The developer machine had a chemical in it that washed away any of the photo-sense material
that was not exposed to the UV light; the soft parts. The PCB was placed onto a rack which was
then placed into the tank for 90 seconds. The pump sprayed the special chemical all over the
board. Upon completion of the 90 seconds, the board was removed and rinsed.
Step 4: Etchant Tank
The PCB had the traces covered with the cured photo-resist material and the remainder of it was
copper. The purpose of the etchant was to remove the copper from the board wherever there were
no traces/donuts. The tank works the same as the first tank that removed the uncured photo-resist
material, except that now the copper will be removed. This process required a higher temperature
that is achieved with a heater within the tank. Upon completion of the 90 seconds it was removed
from the tank. When all the copper is gone the rack was removed and placed in the rinse section.
Step 5: Removal of Photo-Resistant Material from Traces
21
At this point the board had all the copper traces that I needed. Sodium Hydroxide was used to
remove the remaining photo-resistant material from the traces (the hard stuff). The board was
placed in the chemical until the photo-resistant material was all removed. The copper traced were
then revealed.
Step 6: Drilling Holes in PCB and Heat Sink
Next the holes for the components had to be drilled. The sizes used were 1/32”, 3/64” and 5/32”.
The Op Amp holes were drilled with the 1/32” drill. The regulator donuts and the heat sink were
drilled with the 5/32”. The remaining component holes were drilled with the 3/64” drill.
22
Section IV
Power Supply Box
Box Drawing
Figure 18 is the box drawing which was provided. It displays all the views and dimensions of
the provided box.
Figure 18 Box Drawing
23
Box Production
The box to be used as the power supply box was provided. There were no holes in the initial
box. Templates were provided which were then glued onto the box. Below are the box with
the templates glued on with holes already punched.
24
Once the templates were glued on, the box was taken to the lab to be punched and drilled.
25
Section v
Final Assembly and Testing
Once the board was fully complete with all the correct components in the correct location,
wires were attached to the outputs on the board. This made it simple to test the outputs on the
board with a multimeter.
Once testing to ensure that the correct outputs were coming off of the board it was then time
to place the PCB into the box.
Assembly
During the assembly stage the whole box is assembled. This mainly consisted of placing the
binding posts, the fuse holder and the display. This was a very tough task because you had to
be very careful and have great attention to detail to complete this task. Instructions were
provided on how to assemble the box. Below are some pictures of the inside of the box.
26
27
Testing
There are two stages in the testing of the power supply. The first stage is as described above.
Upon completion of soldering all components to the board wires were attached to the outputs
on the board. This made it simple to test that the correct outputs were coming off of the board
with a multimeter. The second stage in testing the power supply was to place the board in the
box, make all the correct connections (with instructions provided), and ensure that the correct
outputs were still coming off of the board and functioning properly. Below is the power
supply displaying the maximum and minimum voltage outputs. There is also the back of the
power supply showing the fuse and power cord.
28
Section VI
Summary and Conclusions
Schematic Drawing
The overall production of the schematic drawing was simple. There was an incomplete
schematic that was given and it had to be completed. This was easy because of my knowledge
on how circuits operate and knowing what component had to be placed where.
Printed Circuit Board Drawing
The production of the circuit board drawing was a little bit more difficult. There were many
rules that had to be followed in order to ensure that the final PCB functioned. The rules were
followed and the board functioned as planned.
Printed Circuit Board Production
The printed circuit board production was very simple. All of the steps were provided, if they
were followed, there were no issues.
Box Drawing
The box drawings were provided but if there was more time in the semester I would have been
fully capable in producing them.
Box Production
Box production went relatively well. The provided templates were placed on the box correctly
(in proper orientation). The only thing left to do was punching and drilling in the lab. This was
simple and went well.
Assembly and Testing
During the assembly and testing I had a minor issue, but other than that it went relatively well.
The only problem that I had was a faulty switch. The switch which was provided did not
function as it was supposed to. When I had determined that the switch was my issue, I simply
replaced the switch and the box worked as intended.
29
Conclusions
The main aims of this project were:
(a)
Complete a schematic and design a circuit board using Eagle,
(b)
Construct the circuit board on Eagle, use the Lab to physically complete the
board, and
(c)
Construct a box to function as a 0-15 V positive and negative as well as a fixed 5
V.
I believe that all of these aims were achieved during this project. Although there were some
minor issues that were run into, I believe that the aims of the project were achieved because
the box was created and functioned completely as planned.
30
Appendix A
Incomplete and Completed
Schematic Drawing in Landscape
31
32
µ
µ
µ
µ
µ
33
Appendix B
Full Size Eagle Schematic in Landscape
34
35
Appendix C
Non Inverted Bottom of Board in Landscape
Inverted Bottom of Board in Landscape
36
37
Appendix D
Punching and Drilling
Templates
38
39
40
41
Appendix E
Front Face Sticker
Template
42
43