Transcript Clip Lloyd

D&T: Electronics and Control Systems
Unit A511: Introduction to designing and making
Name: Alexander Lloyd
Candidate Number: 9177
Centre Number: 16527
The Theme
I have chosen the theme security because their has been a number of cases of
security problems in the newspaper recently and they have all been caused
because of their is no criminal deterrence when no one is in the home. The
product I intend to build improves home security and make the user feel more
secure.
A PIR sensor
detects the
burglar when it is
dark and turns on
a light to deter
burglar
Burglar gets
in because
their is no
security in
the home
A keypad lock is fitted
to the door and if an
incorrect combination is
inputted, then an alarm
goes off
Easy to break in
because their is
no security and
lots of valuable
items in it.
The Theme
Two pressure
plates are
triggered and
then a large
sounding siren
House
Burglary
Sexual
Assault
Burglar
y
Security
Shed
Burglary
A rap alarm is
made and when
the button is
pressed, a large
siren is sounded
for five minutes
A woman is
attacked and
not have a
way of
deterring the
criminal
Temperature of
a bath
A baby is placed in
a bath that is too
hot and then
causes bad burns
on the baby
An alarm is
sounded when
the room gets
below a set
temperature
An elderly person
falls asleep and
then gets too cold
and dies of
Hypothermia.
Elderly
person
A CO2 detector
detects that the
burglar is present
and a large siren is
sounded
The highlighted boxes
shows the choice I decided
to made for my product
A rap alarm is
made and
when the
button is
pressed, a
latched large
siren is
sounded
A thermistor
probe is placed
in the water
and if too hot a
red led is lit
A set of LEDs
indicate the
temperature
and if below a
buzzer is
sounded
This is me conducting a
questionnaire about this
project
User Needs
Domestic Burglaries are on the
rise. so a new product is
needed to help protect the
homes. Below is a picture of a
burglary. Also their is a
newspaper cutting that shows
that their are in the local area.
Some statistics show that
burglaries are on the rise. This
may be due to the current
economic recession.
A burglar in the
act of Burglary
The newspaper clipping shows where most burglaries
that their are burglaries in the occur.
local area. In the clipping, their
was luckily nothing stolen. It
happened during the night
Conclusion
The conclusion is that their is a
need for the intended product. It
must be able to deter the
burglar from the house and
must do it during the night
This is an article of
 a burglary in
the local area
Statistics showing
Burglaries on the
rise
Burglary in Essex
per 1,000 people
10
Burglary in Essex
8
6
2009
8.17 4
2010
7.56
2011
8.23
Burglary in
Essex
2
0
2009 2010 2011
Questions for the Questionnaire
1. Are you out of the home a lot?
This is so I know that their are people who need the product I propose.
2.Would you want their to be a switch to turn off the system?
This will allow me to decide to put a switch in because the users needs it.
3. Would you want the light to go off after some time?
This will allow me to decide whether to have a latch or not.
4. Would you want the time the light is on is be adjustable?
This will determine what type of variable resistor I will use.
5. Would you want it to run on mains power?
This so I can decide a power source.
6. Would you want more than one light to go on?
This is so I know whether another light is needed in the circuit.
7. Do you already have security devices in your home?
This will determine whether their is a potential for my product .
8. Do you want it to be house in a box?
This will determine whether I need to get a box for my product.
9. Do you want it to have a power indicator?
This is so I know whether a LED indicator is required.
10. Would you want a delay after the burglar has been detected ?
This will allow me to on parts of the circuit that is required.
The Questionnaire
The results of my questionnaire:
Questionnaire
Questions
Yes
No
1. Are you out of the home a lot?
7
3
2.Would you want their to be a switch to turn off the system?
6
4
3. Would you want the light to go off after some time?
9
1
4. Would you want the time the light is on is be adjustable?
6
4
5. Would you want it to run on mains power?
2
8
6. Would you want more than one light to go on?
1
9
7. Do you already have security devices in your home?
3
7
8. Do you want it to be house in a box?
5
5
9. Do you want it to have a power indicator?
8
2
10. Would you want a delay after the burglar has been detected ?
7
3
The Trend of the Questionnaire
These results show that people are out of the house a lot. Also the target
audience don't have a security device . With the proposed product, they want a
light that goes off after an adjustable amount of time and that it has batteries
with a switch so that it can be turned off. It must also only run one light with a
delay and have a power indicator.
Product Comparison
Product
Cost
Typical user
When / Where
used?
function
400 watt halogen flood
light
£6.00
Wickes
Used to light a driveway
so the person arriving
in the dark can see up
their driveway.
Terns on when their is
motion in front of the
sensor has a variable
timer to turn the light
off.
AA7-LCD GSM Wireless
Home Security Burglar
Alarm
£324.99
Amazon
It is used in an office
where there is a risk of
burglary at night when
no one is in the office.
Many Inputs into a large
sounding alarm and
also sends you a text
message saying that
the alarm has gone off.
Friedland Response ML1
Shed Alarm
£16.48
Amazon
A person with a Shed at
the end of the garden
and the owner is
concerned that in the
night tools will be
stolen.
Type in a pre-recorded
four digit number that
then gives you 20
seconds to open the
door and has an alarm.
Technology used
Light
Sensor
Light
Motion
Sensor
It has multiple inputs that
detect whether the case of
the alarm is being remove.
It can have a total of 40
inputs and different outputs
including alarm and calling a
preset number.
Die-cast Aluminium
and PCB with
components
soldered.
Aluminium case
with Printed circuit
board.
Injection moulded
plastic with PCB.
Reed
Switch
Alarm
Key Pad
Manufacturin
g process
used
Trend of product Comparison
The trend of the three products is that the more expensive the product, the more reliability the product
has. Also the cheaper the product, the cheaper the case. Another point is that the more it costs, the
more features.
Explanation
This is because electronic components cost money and the more features it has the more components
needed for the intended purpose.
Evidence
The evidence is that the Halogen light bulb is a simple circuit and has few features so it is cheap. The
Shed Alarm has a cheap Case but has a larger circuit so more components are used increasing the
price. The large alarm system has a huge circuit with so many add-ons, this is why it costs so much.
Design Brief
• The device I propose will enhance security in your home. It will deter burglars by turning on a
light inside of the home so it seems that someone is inside. The product will be inexpensive by
using cheap parts. I will use circuit wizard 2 to help design the circuit.
Product Analysis
400 watt halogen flood light
£6.00
Outdoor LED Floodlight 9w With PIR Motion Detector
£37.95
Function
Shines light when dark and motion detected. Amount of time
light is shining is adjustable and how dark the light comes on is
also adjustable.
Shines 130 LEDs when motion detected and dark outside. It then
turns off after a preset time which is adjustable.
User need
fulfilled
The user needs are almost fulfilled but the product does not turn
on a light inside.
This product almost fills the user needs .
Materials
used in
construction
Material used are: Plastics, PCB.
Materials used are Plastics and PCB.
Durability of
product
This Product ins very durable because of it basic shape and fail
safe circuit.
This product is very uncomplicated shape and a simple circuit
making it very durable.
Sustainability
(6Rs)
The halogen light uses 400 watts of power. Lots of useful parts in
side of device. It has no built in opalescence except the light
breaking.
The LEDs can be used because of their low voltage and lots of
useful parts in the floodlight. It has no built in opalescence .
400 Watt Output.
Uses 9W of power to shine 200watts from the LEDs.
Life cycle
Energy use
Trend
These product show that a higher priced light means that it uses less power but do not get a higher power rating the larger the price.
Specification
Description
Explanation
Evidence from Research
1.
This will put off a burglar because he will think someone is
in the house.
2.
The will allow the server to work as the design brief says. If
it wasn't like this, then it will turn on in the day when the proposed
product will not be very effective
3.
The NAND is needed because a negative spike is required to
trigger the 555 Timer and the NAND will provide this.
4.
This is so it meets the design specification
5.
This is because lot of components run on this voltage.
6.
The user is able to turn the system off and when required.
7.
This is so the user when it is on.
1.
The Newspaper Article in User Needs shows a burglary
happening at night. If the proposed product was in place this may of
not happened.
2.
The Newspaper cutting shows that a system with a dark
sensor and motion from the burglar will be required for this to work
to a full potential.
3.
The Questionnaire shows that the light need to be on for a
short time. A 555 timer is the best option because it can have a
variable controlled time and this must be trigged with a negative
pulse,. This is also asked in question 4, it ask whether a variable
amount of time is required, the results show 6 people said yes,
4.
The Design Brief says it will turn on a light in the home and
a lamp will make the product more affordable and simplest option
will mean it is more reliable because of it simplicity.
5.
Question 5 on my questionnaire concluded that 8 of the 10
wanted it to be run on batteries
6.
Question 2 asks whether a switch is required, the results
show that people want a switch.
Functional Specification
1.
My proposed product will detect when a person is walking
up the driveway and will turn on a light in the house.
2.
The System will need to sense whether its dark and if the
burglar is detected.
3.
An NAND Gate will be used to combine the inputs so it goes
on with motion and when it is dark.
4.
The output will be a lamp.
5.
It will be powered by 9volts.
6.
This proposed product will have a SPDT to act as an on/off
switch.
7.
It will have a power indicator.
Physical Specification
1.
The Circuit board will be made using ultra violet etching.
1.
This is to reduce the possibility of a short circuit.
1.
This is because it is easy to use and has all the components
I need.
This will be done by checking the quality of the product as I
build the circuit, this is to ensure their are no errors in the
wiring and placing of the components so the product will
work for its intended purpose.
Manufacturing Specification
1.
2.
It will be designed using Circuit wizard 2.
I will ensure that the circuit will be well built and work.
2.
1.
2.
N/A
N/A
System Diagram
Delay before
input
Input
Combine Inputs
Delay after
Inputs
Process
Delay before
Output
Output
30 Seconds
After a switch is
turned on
PIR Motion
Detector
AND
30 second delay
Transistor
0 Seconds
Relay
0 seconds
Heat Sensor
OR
1 minute delay
MOSFET
30 Seconds
Power Indicator
15 seconds
Dark Sensor
NAND
0 seconds
Darlington Pair
1 Minute
Siren
2 minutes
Infrared Laser
beam break
NOR
10 Seconds
Thyristor
2 minutes
Lamp
EX-OR
2 minutes
555 Monostable
The Highlighted boxes indicate the
building blocks I plan to use
Ideas for Circuit
When the switch is closed and is dark and
motion is detected (the 3-pin terminal block)
the NAND gate triggers the negative trigger
pin on the 555 and then stays in for a certain
amount of time. It closes the relay pins.
Inputs
Outputs
Dark sensor
Relay
Advantages
Disadvantages
•Very Simple
•AND gate does not work with
the 555 timer
Motion sensor
When it is dark and motion is detected (the 3-pin terminal
block) the AND and NOT gate triggers the negative trigger pin
on the 555. The two inputs turn on the AND gate and the NOT
gate inverts it . This triggers the negative trigger pin and then
stays in for a certain amount of time. It closes the relay pins.
This also has a power indicator.
Inputs
Outputs
Advantages
Disadvantages
Dark sensor
Relay
•The 555 will now
•Too many Integrated circuits
Motion sensor
LED
Indicator
Ideas for Circuit
When it is dark and motion detected the
AND gate triggers the OP amp and then the
short negative pulse to trigger the 555
timer chip which then has a delay to the
relay. It also has a power indicator.
Inputs
Outputs
Advantages
Disadvantages
Dark sensor
Relay
•Works very well
•Very complicated
Motion sensor
LED Indicator
When the dark sensor and motion is
detected it triggers the AND gate which is
amplified by the transistor to create a
short negative spike which triggers a 555
timer. This is then connected to the relay.
It also has a power indicator.
Inputs
Outputs
Dark sensor
Relay
Motion sensor
LED Indicator
Advantages
Disadvantages
•Works very well
•Very complicated and has too
many components.
Development of the chosen circuit
This is the first circuit
This detects motion and
triggers a lamp.
I added an AND gate because
the circuit description is that
it needs to be dark and motion
detected.
I added a power indicator
so the user knows it is on.
Development of the chosen circuit
I also added a monostable because it
needed to be on for a certain amount of
time.
I finally added a delay because it
needed a delay before the output
was on.
The Testing of the circuit
The four PCBs below
are the development
while the PCB to the
right is one that does
not work because it
tracks overlapped.
1.
The PCB
2.
Here I have expanded the
circuit and got rid of the rat
nest. But their was still a lot
of blue wires so I moved the
components further.
The NAND inputs have all been
grounded so that a static charge
built up will not affect the input
used.
Their was a ‘rats nest’ here
so I expanded the
components.
3.
4.
Here I continued to
move the
components and was
able to remove all but
two blue wires.
Here is my final
circuit.
The Final PCB and Bill of Materials
Name
1000μF Electrolytic Capacitor
200μF Electrolytic Capacitor
100KΩ Potentiometer
1MΩ Potentiometer
330Ω Fixed Resistor (1/4 Watt)
4011 Quad 2-Inout NAND Gate
NE555 Bipolar Timer
Green LED (0.2in , 5mm)
Light Dependant Resistor (OPR12)
ZVN3306A N Channel MOSFET
PIR Sensor
Signal Lamp
PP3 Battery Snap
3.2 (W) x 2.3 (H) Printed Circuit
Board
Cost
£
0.19
£
0.19
£
0.79
£
0.79
£
0.01
£
0.14
£
0.15
£
0.05
£
0.93
£
0.22
£
7.15
£
1.99
£
0.25
£
2.88
Quantity Total
£
1
0.19
£
1
0.19
£
2
1.58
£
1
0.79
£
1
0.01
£
1
0.14
£
1
0.15
£
1
0.05
£
1
0.93
£
1
0.22
£
1
7.15
£
1
1.99
£
1
0.25
£
1
2.88
Total:
£ 16.52
The Testing of the PCB
Planning for Manufacture
Description of process
Equipment required
Safety issues
Tips for success
Design PCB and Mask.
Circuit wizard 2 program
None
Remove as many blue wires. No rats nests
(green wires) Test circuit at each stage of
development
Cut board to size
Band Saw
Don't touch saw, its Sharp. Blade will also
be hot after cutting. When blade is
running, keep hands away
Measure Board accurately. Cut carefully.
Do this process quickly because the
copper clad starts to oxidise.
Expose mask, and PhotoPCB to UV light for
4 minutes.
UV light
PhotoPCB
Mask of my circuit
Make sure the UV light is covered up
because UV light will damage eyes
Expose board for around 10 minutes
Develop exposed PCB
Development Fluid
Wear Goggles and safety equipment.
Development fluid is an Acid. It is
corrosive.
Wear correct safety clothing
Etch PCB
Bubble etch tank
Etchant
Etchant Corrosive. Avoid getting on skin. If
you do, wash off quickly.
Wear goggles and gloves. Leave in etchant
for 1 – 2 minutes.
Drill holes
Drill
Drill Press
Don’t put hands on near drill bit. Wear
goggles because fragments of material
may go into your eyes.
Make sure drill is centred over pad.
Solder chip sockets
Solder
Soldering Iron
14 pin chip socket
8 pin chip socket
Soldering iron is hot. Don’t melt the plastic
socket. Solder is from lead. Handle with
care.
Make sure all pins of the socket are
correctly placed before and during
soldering.
Solder Resistors
Solder
Soldering Iron
Fixed Resistors
Variable Resistors
Soldering iron is hot. Avoid overheating all
resistors.
Use the correct value resistors. It does
not matter what way the fixed resistor is
fitted and soldered but the variable
resistors have three pins that have to go
in the right way
Planning for Manufacture Continued
Description of process
Equipment required
Safety issues
Tips for success
Solder Capacitors
Solder
Soldering Iron
Capacitor
Soldering iron is hot.
The electrolytic capacitors need to placed
in the hole the right way. Electrolytic
capacitors have a negative line along the
side so you know what way to place the
component.
Solder LED
Solder
Soldering Iron
LED
Soldering iron is hot.
Solder the LED the right way,. The Cathode
is the negative side and is marked by a
longer wire and also the led has a sector
of the led removed which also means the
negative side
Solder MOSFET
Solder
Soldering Iron
MOSFET
Soldering iron is hot.
Solder the MOSFET the same way as the
picture printed off of the circuit. IF the
MOSFET is the wrong way, then the
MOSFET and the circuit may be damaged.
Solder off board components
Solder
Soldering Iron
Wire
SPST Switch
Bulb
Light Dependant Resistor
PIR passive infrared sensor
PP3 Battery clip
Soldering iron is hot.
The Battery, and PIR must be put in the
way that is on the picture. The others can
be placed any way round but must be in
the allocated holes on the PCB.
Shrink wrap connections between off
board components and wires
Solder
Soldering Iron
Heat Gun
Heat-sink
Soldering iron is hot.
Shrink Wrap is a very quick process heat
carefully and accurately.
Add chips to chip sockets
555 timer chip
4011 Quad Dual input NAND
Soldering iron is hot.
Add the chips carefully and make sure the
terminals are not overlapping.
Tools
Wire Cutters
These are wire cutters. They are
used to cut wire either to shorten
their length or to cut away from the
rest of the reel of wire.
Soldering
Iron
Wire
Strippers
Heat Gun
The soldering iron is used for
soldering components to the board
using solder. It uses a compound of
lead and copper to melt when heated
and then solidify to the board. This
then makes it a good conductor and
stays on the board. It also causes the
joint to be secure so that a short
circuit not take place.
The wire Strippers are used to remove
the outer sleeve of the wire. This means
that they can be tinned and soldered to
the PCB or components.
The heat gun is used to heat the heatshrink rubber to the wire and off board
components. This makes the
components and wire less likely to
break.
Soldering
Iron Holder
The soldering iron stand is used to hold
the soldering iron. It is a safety
precaution so that you don’t burn the
table or yourself. Also it carries a
sponge which you wet to clean the
soldering iron.
Small Nosed Pliers are used to Small
bend resistor or capacitor wires
so that it is easier to solder to the Pliers
board. They also allow you to hold
the components while soldering so
you don't burn yourself.
The multi-meter allows the user Multi
to test many measurements
including amps, volts, resistance
or even whether a components
works when it is meant to. This
then allows the user to pin point
if a components or part of the
board is working.
Nosed
Meter
Manufacturing the circuit, the PCB
1.
2.
3.
4.
First the PCB has to be printed on
Place the treated board into the
glossy flexible transparent plastic. A
etching tank, this is a very
laser printer will need to be used
difficult part because if over
because laser ink does not dissolve in
developed, then the board may be
the etching fluid. The Ink protect the
unusable.
copper to make the tracks.
Stick the PCB to a pre-cut to size the 5. Drill the holes for the PCB. This is
Copper clad. The copper must be the
done by using a 1mm drill bit in a
same size as the print out border of
small pillar drill. Align the drill
the PCB. It may have a protective
with the where you want to drill
plastic over the photo-resistant, if so
the hole. Then with the board held
then take it off and go on to the next
tightly push the pillar drill into
step
where you want the hole.
Note that some components such
Place the Copper clad and Printed
as variable resistors will need
out PCB in the ultraviolet light
bigger holes. The PCB is now
where this will cause a chemical
ready for soldering components
change to the unprotected copper
on.
and it becomes easier to etch later
on.
Manufacturing the Circuit, the soldering
To start off, I soldered wires to the
off board components to wires so
that they are off the board. To do
this I got a piece of heat shrink and
covered a tinned wire and the
component so that they are
connected. Then I tinned the other
side of the wire so that it had a
little solder on. I did this for all the
switch, LED, bulb wires, LDR and
PIR sensor.
Next, I used the heat gun to add
heat shrink to the wire so that the
joint between the wire and the
component was more secure and it
meant that the wires could not
short circuit. It also meant that
the wires had a small degree of
water proofing so that it could be
used outside.
This is the PCB without any
components on the board. I
started the soldering by
soldering the variable
resistors on to the board.
Here I soldered the
variable resistors. This
soldering went well
and the joints looked
good.
This is me soldering
the potentiometers
to the board by
placing a little solder
on the soldering iron
and then placing on the resistor with the solder
to create a even joint.
Manufacturing the Circuit, the soldering
Next was the resistor. I
first made sure it was the
right one. It should be
330Ω resistor. This
should be orange orange
brown. In the picture you
can see that this is the
right resistance.
I was going to put in the large
1000μF capacitor but I
encountered the problem that
the capacitor went over the
wire so I soldered the wire in.
The picture below shows the
capacitor on top of the wire.
The wire has insulation so that
the metallic base of the
capacitor does not cause a
short circuit
Then I realised that I had
soldered the capacitor pads
together. This would cause
the charge of the capacitor
not to happen and a low
resistance route to the
negative terminal and the
MOSFET would not trigger.
This was resolved by using a
solder sucker. The picture
below is the capacitor fixed.
Then I soldered the 200μF
capacitor in with no
problems. I made sure to
check if they were the right
way because these
capacitors are electrolytic
which means that they are
polarised so they need to be
placed in the right way.
Manufacturing the Circuit, the soldering
Now I soldered the off board components to the board. I
The chip socket was soldered started with the PIR, then the Light dependant resistor, bulb
next. I soldered the notch in wires, LED, switch and lastly battery. I looked at a picture of
the circuit printed off circuit wizard so that I knew the right
the same way as the chip
way to place polarised components such as the PIR and
notch. This is because the
battery. Then the NAND gate and 555 timer chips were
chip will not fit in if the
sockets not in the right way. placed in the appropriate chip socket. This had to be placed
carefully because the chip pins could bend and the chip may
The MOSFET was then
be unusable. Also your static may damage your chip.
soldered in with no
problems. It has too be
When testing the circuit, I
placed in the right way
noticed that the bulb was alit
because it is polarised. If
a little. I then realised that the
placed in the wrong way,
battery was wired the wrong
then the MOSFET would get way round. This occurred
damaged and the circuit
because the red and black
will not work.
looked similar on a black and
white printout. This was
corrected and the circuit
tested again. I then went on to
the test plan.
•
•
•
•
•
Problems when manufacturing the circuit
When putting in the potentiometers, the holes were too
small, so I used a small drill to increase the size of the
holes. Then they fitted in.
The 1000μF capacitor was very big and overlapped a
wire. So I soldered the wire in first with insulation on
so it would not short circuit. Then the capacitor went
on top.
Then while checking the pads after soldering, I noticed
that I had used too much solder and they had caused a
large joint. This would mean that the circuit would not
work so I used a solder sucker and removed the solder
and then soldered the joint again.
The PIR was faulty so that the circuit would operated
differently to the expected result. This was changed and
a tested working PIR sensor was soldered in.
The battery snap was not soldered in the right way
because the red positive and black negative looked
similar on the black and white circuit diagram. This was
corrected and the problem was resolved.
The finished circuit
This is the component side
of the circuit.
This is the solder
side of the circuit
This is the complete circuit
with off board components
Testing Plan
Testing Plan
Test
Expected Result
Actual Result
Result (✓or X)
Turn on the circuit using the switch.
A green LED should turn on.
The LED did not turn on but the bulb was on a
little. I quickly realised that the battery snap
was in the wrong way. The bulb went on
because it is no polarised. I then re-soldered
the battery snap the right way.
X
Take outside during the day. Trigger the PIR.
This should not have any response because the
NAND does not trigger the 555 timer. Using a
voltmeter, pin 3 of the 555 should be 0 Volts
and pin 10 should be around 9 volts.
Their is no response. This meant the product
was working the way it should of.
✓
Place in a dark place. Then trigger the PIR
again.
A little wait but will go on for 2 minutes. This is
because the inputs trigger the NAND and the
rest of the circuit. Then if the middle 100K
Potentiometer is at 0Ω, then the time constant
will be 0 Seconds but at full resistance 100K it
should stay on for
It went on but not for 2 minutes. This meant I
had to adjust the middle variable resistor . This
would mean the timing would work to the
specification.
X
Wait until the light goes on and then off. Trigger
PIR again.
This should turn on the bulb same as the last
test in staying on for 2 minutes.
Because the variable resistor was adjusted in
the last step in the test plan, then circuit
worked to the way the specification states.
✓
Turn off the switch. Now trigger the PIR once
again
The LED should not be on and the bulb should
not be on.
The switch is wired in correctly so this worked.
The LED and bulb did not go on.
✓
Evaluation
Description of process
What went well
(What did you do to avoid errors)
Problems encountered or changes made
Action taken to deal with problem
Design PCB and Mask.
Using Circuit Wizard to design the PCB to remove rats
nests and shrink the board in order to reduce amount
of copper clad used.
When attempting to shrink the board by moving the
components and tracks, the software would join tracks
together which would mean the circuit would not work
to the specification.
Going back to an old copy of the PCB and then taking
great care in moving tracks would mean that the PCB
would work to how i wanted it to. Also testing the
circuit regularly will show I problem if it worked
differently to how i wanted it to then i would know that
their is a problem with the PCB and it could pin point an
error.
Cut board to size
Using the band saw by sticking the image to the copper
clad and following the lines of the PCB from the paper.
This meant the sides were very accurate.
No problems were uncounted during this step
No action required.
Expose mask, and PhotoPCB to UV light for 4
minutes.
It was exposed for the right amount of time so that the
tracks were not exposed to little or too much.
No problems were uncounted during this step
No action required.
Develop exposed PCB
The development of the circuit went really well because
it was exposed for right amount of time.
No problems encountered
No Action Required
Etch PCB
It was placed in the etching tank for the right amount of
time so that it looked like a very good PCB.
No Problems were uncounted
No problems were encountered.
Drill holes
I used a picture of the finished circuit printed from
circuit wizard.
The variable resistor holes needed to be a drill size
bigger.
I used a drill bit a millimetre bigger than the last. They
then fitted in with problem.
Solder chip sockets
The solder joints were soldered well.
I changed the order of the plan so that the chip sockets
was soldered before the MOSFET and after the
capacitors.
This was changed because I felt that they would get in
the way of other components
Solder Resistors
The variable resistors now fitted in the holes. The fixed
resistor was soldered very well.
The holes were slightly misaligned but they still were in
the solder pad.
No action was required.
Evaluation continued
Description of process
What went well
(What did you do to avoid errors)
Problems encountered or changes made
Action taken to deal with problem
Solder Capacitors
The finished capacitor looked really good and fitted my
specification of wanting the finished product to look
good.
The 1000μF capacitor was very big and overlapped a
wire.
Then while checking the pads after soldering, I noticed
that I had used too much solder and they had caused a
large joint.
So I soldered the wire in first with insulation on so it
would not short circuit. Then the capacitor went on top.
I used a solder sucker to remove the solder and then
soldered the joint again with less solder and the joint was
good.
Solder MOSFET
To avoid errors, I checked the circuit diagram and that
the drain of the imaged was the same as the MOSFET. I
did this for the source and drain.
No problems were encountered when soldering the
MOSFET.
None
Solder LED (off board component)
I used the PCB picture so that PIR wires were in the
right holes and that the LED, switch, bulb wires, LDR and
battery snap were also in the right place.
The bulb wires were not soldered in properly and fell out
soon after soldering. The PIR was faulty so first test did
not work.
The wires were soldered again and they didn't fall out. The
PIR was replaced with a new one that had been tested to
work.
Shrink wrap connections between off board
components and wires
I advance the heat gun slowly towards the held
component so that the component would not burn.
When I thought the heat gun was close enough (about
40cm), the Heat shrink rubber has shrunk enough.
The switch wires were not quite straight to the heat
shrink so the heat shrink looks like it has a small lump
to the side.
Because the lump was small, no action was required.
Add chips to chip sockets
Two chips needed to be added, the NAND gate and 555
timer. They were placed in by earthing yourselves so
that you have no static charge.
No problems were encountered.
Because no problems were encountered. No Action
needed to be taken.
Test the circuit
I followed the test plan when the LED indicator went on
with no problems.
This was because when it was first turned on, I realised
the battery was the wrong way. This cause the chips to
get hot but i turned the circuit off before any damage
was caused.
I soldered the battery clip in the right way and this meant
the circuit worked.
Manufacturing and Functional Evaluation
Manufacturing
•I think I could have made the Printed Circuit Board
smaller because their are areas in the Board where their
is not a track or a component. This would mean that less
materials are used during the making of the product such
as copper clad and ferric chloride.
•Another option is to solder the LED to the printed circuit
instead of being an off board component. This would mean
less wire is used and would reduce the price of the final
product.
Functional
•If a used this NAND gate delay instead, it would of taken
advantage of the rest of the NAND gates that were not
used and not to have to use the MOSFET. Also it would of
seemed as if the light was switched on instead of what the
final circuit does where it amplifies and goes on gradually.
The specification says that it needed to be turned on as if
it was a switch.
•Adding a test button would mean
the user can test if the bulb is
working. This would be done by
adding a push button between the
drain of the MOSFET and 0 Volts. It
would not cost much to add this to
the PCB.