1. D&T: Electronics and Control Systems
Unit A511: Introduction to designing and making
Name: Jake Robinson
Candidate number:
Centre Number: 16527

2. Creativity
A bath level alarm is handy as it can save you wasting your time waiting for the bath to fill up.
I picked safety because it is protecting you from any harm which is most important. I picked the bath level alarm because it can be put with a temperature sensor to protect both you and your home.

3. If you leave it it might overflow.
WHAT
Problems can be faced at any time when running a bath.
These problems can happen any where
WHEN
WHERE
USERS NEEDS
WHO
WHY
People who want a easy bath experience
You always have
to be there and
wait for it to fill up.

4. Questionnaire
1.Do you have any baths? Reason: Can help make the decision if I should modify the product for a different use. 2.Do you run baths for others? Reason: The user may have kids and there fore it has to be a good temperature. 3.Do you need to be able to leave the room while running a bath? Reason: There is a possibility that the user has to go and attend something else, children etc. 4.Has your bath ever over flown? Reason: The product may be of use if their problem is re-occurring. 5. Do you like to having a perfect but you cant do it right? Reason: I want not only the user to be safe but to be comfortable. 6. Have you ever burnt yourself if your bath was too hot? Reason: Could be an extra feature of my product. 7. Has a child that you know run a bath and injured themselves in the process? Reason: To get a good idea at what age group this product is aimed at. 8.How often do you have baths when you have them? Reason: To find out how often my product could be used. 9. Which would you use more and prefer? Reason: To know what alarm is more predominate. 10.How much are you willing to pay for an item that will solve these things? Reason: To know what people are willing to pay.

5. Manufacturing process used
Product
Cost
Typical user
When / Where used?
Function
Technology used
(Input / Output)
Manufacturing process used
Motion Sensor Alarm + 2 Remote controls
£6. 65 Sold by Galaxy’s
People that need to protect items in their homes when they are away.
It detects
movement and
when it does it
sounds an alarm
Alert people
nearby and to
scare the burglar
Infrared alarm that sound a 110dB siren when triggered. The motion sensor picks up anything in a 6m radius.
Injection moulding was used to make the case and machines to make the circuit board.
Bath Temperature & Water Level Alert Alarm
It detects if the
Water gets too
Hot and to deep
and sounds a
alarm
The Alarm also
includes a water
overflow alarm
system. Digital
temperature
display. Alarms if
water temperature
outside pre-set
level.
It was probably
Made by pour in
moulds as it is water
proof and most
likely rubber.
People who have
baths at any time
In their homes.
£20.99
Wireless Care Alarm
Kit with Large Bed
Leaving Sensor Mat
Ideal for monitoring an
elderly patient who
requires assistance
when getting out of bed.
This system alerts the
carer immediately via
the wireless portable
pager that the person
has left their bed.
Elderly people that
live alone or need
care all the time in
their houses or
elderly homes.
Made by machines
for the circuitry
but maybe
manually
Assembled.
£69.99
Includes a sensor
mat, transmitter
and pager
(receiver).

6. The Trend
I have identified that all of these products are designed to protects something. Whether it be from burglars, water damage from baths or even protecting the elderly from falling out of bed. Generally as the price goes up the value of what the product is trying to protect goes up. The least expensive, the burglar alarm, is protecting the home from people even though a standard home is protected enough. The bath level alarm is protecting the property from long-lasting damage from a bath overflowing. But the wireless care alarm kit is protecting lives which is the most important thing.

7. Examples of products for comparison (all alarms of some sort)
Remember these are examples – you need to get your own
Product Description – Personal Attack Alarm (£5.99) - From Amazon
Tiny matchbox sized attack alarm with a useful key ring attachment. Simply pull pin out to activate alarm. Emits 130 decibel siren Supplied with alkaline battery 5 year no-quibble guarantee. Size: 4.4 x 3.8 x 1.6cm Weight: 20gms .
From Amazon
Product Description – Carbon Monoxide Alarm (£16.66) - From Amazon
Requires 3 X AA Batteries, LCD Display, Approved Test and hush button Alarm memory function, Audio and visual Alarm, Self test function, Highly accurate carbon monoxide detection, Audibility: 1 metre distance Sound and LED indication Standby: Green LED flashes once every 30 seconds Alarm: Red LED flashes quickly with alarms sounding every 5 seconds and repeat Low battery indicator: Sounds every 30 seconds when batteries are lower than 3.3v with green LED, Malfunction indicator
Product Description – Cold Alarm for Old People (£27.50) - From Amazon
Keep warm and stay safe with this affordable and effective alert to the dangers of falling temperatures. Particularly useful for the elderly and less mobile, who are often especially vulnerable and cannot always detect or respond to getting cold, this Cold Alarm provides early warning of colder conditions in the home, so you can take simple steps to prevent ill health. The Cold Alarm delivers early warning of falling temperatures in the form of an easy-to-understand traffic light style LED display, which is backed up by an audible alarm at the lowest temperatures. Green light flashing every 10 seconds shows that the temperature is above 18°C : considered normal safe environment;
Amber light flashing indicates that the temperature is between 12°C and 18°C :take action to increase warmth;
Red light flashing warns of a dangerously low temperature of between 7°C and 12°C : there could be a risk of hypothermia, need to take action;
Red light flashing and beeping alarm alerts to immediate danger of a temperature below 7°C : dangerously cold.

8. Creativity (slide 7) The Design Brief
Summarise what you have found out so far in terms of there being a definite situation, a recognised problem and people who have a need for what you could design to help them.
Write a clear Design Brief that describes clearly what you are going to design and make.
Write down what you need to do next or find out next e.g.
Decide in detail what your circuit is going to need to do to solve the problem.
What circuits and components might be available for you to use.
What software you have available to you, to help you solve the problem and design a solution.

9. The Design Brief
So far I have discovered that there is a need for water level alarms with a temperature sensor to keep the user and the property of the user safe. This is because people can burn themselves in hot water and this can be fatal to bath users such as children.
I am going to design a product that can detect water getting too hot or too high especially to alarm the users if they are in a different room.
My circuit is going to have to detect heat and the height of water.
I could use probes to detect the water height and a thermistor to detect heat.
I will be able to use Circuit Wizard to aid me in making my product by helping me plan how my circuit will work.

10. Creativity (slide 8) Product Analysis
Analyse in detail 2 products related to your project (probably 2 different types of burglar alarms, one fairly simple and one a little more complex.)
Use the table on the next slide to help you organise the information.
A simple system for the hotel room on holiday.
A more complex system for the home.

11. Name and picture of product 1 Name and picture of product 2
Creativity (slide 9)
Use 10 or 12 point text in this table
Name and picture of product 1
Name and picture of product 2
Function
User need fulfilled
Materials used in construction
Durability of product
Sustainability (6Rs)
Life cycle
Energy use

12. Bath Temperature and Water Level Alert Alarm
Magiplug Bath Overflow Plug and Temperature Plug
Function
Detects the water level and temperature of a bath and alerts the user.
Detects the water level doesn’t let I overflow by empting it slowly and it detects temperature of a bath and alerts the user with the use of a led changing colour.
User need fulfilled
Protects their home from water damage and injury from burns.
Materials used in construction
Rubber, Digital temperature display
Plastic, rubber
Durability of product
Rubber absorbs damage and makes it water tight.
Rubber makes it water tight and the plastic makes it better under pressure of the water.
Sustainability (6Rs)
The rubber an be easily recycled but the display not be able to. Reusable in any bath. There is some aesthetic excess rubber that could be reduced. It is small and uses small batteries so it doesn’t waste power. Hard to repair as you would have to remove the waterproof seal.
The plastic an be easily recycled along with the rubber.
Reusable in any bath or sink. It could be made so the water intake takes up less material. It is small and uses small batteries so it doesn’t waste power. Hard to repair as you would have to remove the waterproof seal.
Life cycle
* Not clear on what this means
Energy use
Uses 2x AAA batteries.
Uses 2x AA batteries.

13. Design (slide 10) The Specification
Summarise the information to produce a list of points that describe what your “product” will need to be like to solve the problem.
Remember that you are only describing what the circuit will need to do to solve the problem.
This list of points is the “specification”
Function:
What it needs to sense – inputs
What it needs to do when whatever is sensed – output
Include any timings if appropriate – delays etc.
Include indicators etc.
Power supply.
Safety features.
Manufacture / construction.

14. Specification My product will have to be: Watertight Small/ compact
Accurate
It will have to detect heat
It will have to detect water levels.
Inputs: Water level (probes) and heat(thermistor).
Outputs: Siren (for if the bath will over flow) and Bi-colour LED (to show you I its to hot or cold)
Indicators: LED to show that the product is on
Power supply: 9V battery that can easily power the circuit.
Safety features: Water tight so the circuit doesn’t break in the water
Manufacture/ construction: To be done by hand and the circuit will be design on Circuit Wizard to decide the best way to make the circuit.

15. Design (slide 11) System Diagram
Show a systems chart to show possible inputs, outputs and processes.
Show pictures of the components required for each input or output mentioned.
Do not include combining inputs and delays if not appropriate to what you are designing – although you could use the columns to show that the response is immediate. (i.e. 0 seconds.)
Delay before INPUT
INPUT
Combine inputs?
Delay after INPUT
PROCESS
Delay before OUTPUT
OUTPUT
Time delay between power on and input sensed?
List of possible things that could be sensed + images of possible components.
More than one input that needs combining? – e.g. AND or OR?
Time delay after input sensed?
List of possible ways that the output can be controlled.
Time delay before the output is turned on.
List of possible outputs ( include power indicators etc.) + images of possible components
Delete these instructions from your table.

16. System Diagram INPUT PROCESS OUTPUT Transistor Buzzer Monostable Siren
Delay before INPUT
INPUT
Combine inputs?
Delay after INPUT
PROCESS
Delay before OUTPUT
OUTPUT
No delay instant activation
Thermistor (heat)
No combination
No delay
Transistor
Buzzer
Probes (water level)
And Gate
Monostable
Siren
Or Gate
Astable
LED

17. Design (slides 12 and 13) Slide 10 – Ideas for the circuit
Include 3/4 circuits that could solve the problem:
Picture of each circuit – from internet, hand drawn and scanned in or from circuit wizard.
Brief description of the circuit saying what does in terms of what it senses and how it controls its outputs.
How well it could it solve the problem?
Slide 11 – Development of the chosen circuit
Choose one circuit and give your reasons for choosing it.
Build it in circuit wizard
Show screen shots of the circuit being developed – component values being changed to fine tune the way it works (especially in terms of timing delays etc.)
Show annotated screen shots of the circuit being tested to show that it will work and that it will solve the problem.
It is important that at least three annotated stages are shown of the circuit being developed, that the screen shots show it working so that it is clear that it solves the problem.

18. Ideas For Circuit
This circuit detects when the water level is too high and if the bath is at risk of overflowing. It uses a float sensor to detect the depth and has a astable to make it clearer to the user that there is a problem by making the circuit buzz on and off.
I think this circuit is good because of the astable, this allows the circuit to be more noticeable by the user. But the buzzer could be quiet so it would be hard to hear.
This circuit detects water level also but to make this more noticeable there is a siren which is much louder and can alarm the user anywhere. It also uses a operational amplifier which can make the circuit very sensitive.
This is a good circuit I believe because of the siren which is loud enough to be heard anywhere in the house potentially.
This circuit uses a thermistor to detect a high temperature that could potentially burn someone or could be fatal if quite young.
I think this circuit could be good as it focuses on the safety of the user rather than the property which is more important.

19. Design (slide 14) Development of the PCB
Show the stages of the development of the finished circuit into the final PCB
You must show at least 3 stages of development.
Each stage must be annotated to describe the changes and the reasons for them.
The final PCB must be shown including the off board components and the connecting wires – it would be a good idea to label this final stage.
The list of components must be included – images of the components to be used could get extra marks. (from earlier in the project?)

20. Circuit
This is where I decided to add a combination of three separate levels of water probes. The push-button switches represent the probes in the water.
This shows the temperature sensor that I implemented into my circuit. This was going to be my original circuit
This is my final circuit, it has a combination of both a heat sensor with a buzzer and LED. It also has water level probes, on the first and second level they have two separate LEDs to show how high the water is and on the third and highest level it has another LED and a buzzer to alert the user.

21. Circuit working This is the circuit when it only has been switched on.
The first level has been switched on, the LED has switched on.
The second level has been switched on, another separate LED has switched on.
The third level has been switched on, another separate LED has switched on as well as a buzzer.
On the left is the part of my circuit where it is at 30˚ and the LED and buzzer is off, but as soon as it goes above 40˚ both the LED and buzzer turn on until the temperature is lowered.

22. Circuit Working Video

23. PCB This is my original circuit that has not been changed at all.
This is the part of my circuit were I made an error. I made all the pads round and larger. This was a problem with my the oval pads on the LEDs and thermistor. This made the circuit pointless, I noticed this and quickly rectified it.
This is my circuit that has been finished but the pads have not been modified.
This is my circuit with the proper pad sizes and has been made compact. Unfortunately I was not able to remove the last blue wire as it would make the circuit much larger.

24. PCB working The circuit has been turned on.
The second level has been switched on, another separate LED has switched on.
The first level has been switched on, the LED has switched on.
The third level has been switched on, another separate LED has switched on as well as a buzzer.

25. PCB Working Video

26. Description of Process Tools/Materials required
Making (slide 15)
Planning for manufacture
Use the table below to describe how you plan to make your circuit.
Use the information and pictures of equipment on my website to help you.
Description of Process
Tools/Materials required
Tips for success
Design PCB and create mask
Cut board to size
Expose Mask and photoPCB to UV
Develop exposed PCB
Etch PCB
Drill holes in solder pads
Add resistors
Add capacitors
Add transistors/thyristors
Add Chip socket
Add off board components
Add chip to socket
Delete any of the processes that don’t apply
You need to add detail to this column for each process

27. Description of Process Tools/Materials required
Safety Issues
Tips for success
Design PCB and create mask
Circuit Wizard 2 program
Make sure the circuit is completely working before manufacture.
Cut board to size
Band saw
When the saw is turned on keep your hands away from the sharp blade. Wear eye protection as the saw could potentially produce dangerous shards. It will also be hot after use.
Confirm that you have the correct measurements to ensure you cut yourself a piece that is too small.
Expose Mask and photoPCB to UV
UV light
PhotoPCB
Mask
Do not look at the UV light, or cover it up. It can damage you eyes and others
Expose for 10 minutes
Develop exposed PCB
Development liquid
Avoid skin contact with the liquid. Wash off any that splashes onto your skin immediately.
Try not to over develop the board, as it will make the circuit fade and not work.
Etch PCB
Bubble etch tank
Etchant
Take care to avoid splashing as it will stain anything it touches.
If you are warming up the Etchant, have it done under a fume hood and be careful how hot you get it.
Drill holes in solder pads
Drill
Wear protective eye wear so that there is no risk of damage to your eyes.
Be certain that you have the drill in the center of the pad and that you have the same size.
Solder resistors
Soldering equipment
Resistors
Be careful not to burn yourself, the iron will be hot during and after use.
Do not solder off the pads or the tracks.
Solder transistors
Transistors
Solder off board components
9V Battery

28. Making (slide 16 to 18 - approx)
Manufacture of the circuit
Include photographs to show the stages of the making of your circuit
Annotate each picture to show what is happening.
Highlight any problems that were encountered and what you did to solve the problem or anything that you changed as the circuit was constructed (i.e. what is different to what you planned. This is an important part of the mark scheme.
In addition:
You must include a clear photo of the whole circuit including the off board components and the connecting wires.
You must include a clear photo of the top side of the PCB showing the components.
You must include a clear photo of the underside of the PCB showing the soldered joints.
To ensure the marks for problem solving are gained it might be best if the changes mad and the problems encountered are summarised at the end of this section.

29. Making the circuit
This is my fresh PCB before I have soldered anything onto it.
Then I added my flying wire and my variable resistor. The holes that were made were too small for the variable resistor so I had to use a small drill piece to enlarge them.
Firstly I soldered the resistors, while doing so I encountered no problems. After that I added the transistors and I had to bend the wires a lot to fit it in as close to the board as I could.
This is a picture of the water level probes that I had to make. In order to do this I had to put two sets of terminal blocks on a piece of wood. The wires used as the probes had to be different sizes except for two as the first is the positive wire.

30. Making the circuit
This is my circuit with all components soldered in. This includes my LEDs, thermistor, battery snap, water level probes, transistors, variable resistors and the resistors.
I encountered a problem where I had joined two pads together with solder, if I had not noticed this my circuit could have short circuited.
Note: I will be putting in a photo of all my components on the top side of the board here, but I forgot to do so last time.
Immediately I rectified this problem by using the de-soldering tool and then I resoldered the joints correctly.
As my circuit is associated with water I needed some of the components to be waterproofed, so I put a shrinking plastic over my switches, LEDs and my thermistor’s joints that were joined to a wire.

31. Evaluation (slide 19) Testing your circuit
Show a step by step plan that can be used to test your finished circuit. Write it as if it were for a person who does not know how it is supposed to work.
Tick of each step to show that the circuit works.
Evaluation
Describe what went well and what did not go so well in the manufacture of your circuit
Consider the development of the circuit and the development of the PCB
Consider the actual building of the circuit
Could it have been made differently? – alternatives?
Could it have been made better? – how?
Compare what you did to the steps of your plan
See table on next slide as a suggestion.

32. Evaluation (slide 20) Evaluation (continued) Description of Process
What went well
Problems encountered/changes made
Action taken to deal with problem
Design PCB and create mask
Cut board to size
Expose Mask and photoPCB to UV
Develop exposed PCB
Etch PCB
Drill holes in solder pads
Add resistors
Add capacitors
Add transistors/thyristors
Add Chip socket
Add off board components
Add chip to socket
Copy the planning table and edit as required.
Comments only need to be brief.

33. Evaluation (slide 21) Improvements
In addition to describing how the circuit could have been manufactured better;
Describe how the circuit could be improved to function better to solve the problem more effectively.
Different inputs
More inputs
Different control of the outputs
Different outputs