D&T: Electronics and Control Systems

Unit A511: Introduction to designing and making

Name: Matthew Spicer

Candidate number:

Centre Number: 16527

Creativity (slide 2)

Theme Choice

SecurityFloodalarm

Burglar alarm

Baby

Personal protection Old

person alarm

Night light

Pet

BathPool alarm

Door lock

alarm

Rape alarm

Attack alarm

water

food

Water temp

Water level

key

Passcode

Water level alarm

Movement

Vibrational alarm

bathcrying

Heat

I am going to choose the theme security and personal security because I feel there is a need for my theme.

USERS NEEDS

It will be used when ever the user is

having a bath

It will be for all bath users who can

not read a thermometer and maybe for children

It could prevent fatal or

minor burns

It will be used in baths mainly in the

home

It will be able to sense the

temperature of the water and notify the user

Investigation of Users’ Needs

Designing (slide 3)

Creativity (slide 4)

Users Needs• The user needs a devise to worn them if the water is too hot or too cold

(WHAT):• From the sun newspaper: A MOTHER today told how her toddler daughter was fatally scalded in the bath when she turned

her back for just a couple of minutes. (Picture A) • A three-month-old girl from Surrey, B.C., has been airlifted to hospital after suffering severe burns while being bathed in a

kitchen sink.

• (WHO): • The main users are mothers.

• (WHERE):• At the average home with a bath

This proves there is a need for my product and it shows that my product could prevent deaths and burns from happening

QuestionnaireQuestionnaire

x 1 2 3 4 5 6 7 8 9 10

Do you have a child ? yes yes yes yes yes yes yes yes yes yes

Are you aware of the danger of an over heated bath ?

no no yes no yes yes no yes no no

What temperature do you think is safe for a baby bath ‘c ?

20 30 33 37 15 40 20 37 37 30

what do you think is the best warning system ?

LED LED Sound LED Sound LED LED Sound LED LED

How much do you want to pay for a warning system ?

£10 £12 £20 £10 £ 15 £15 £15 £20 £30 £10

do you know how to read a thermometer ?

NO NO YES NO YES NO NO YES NO NO

How often does your house hold have a bath per week?

2 7 2 5 6 2 4 4 5 6

Do you think there is a need for a devise ?

YES YES NO YES YES YES YES NO YES YES

Questionnaire1. Reason: It shows me if the consumers have a personal need for the product. The results

of this question show that lots of people have children and that my product will be very helpful to cautious parents.

2. Reason: I asked this question to see if people were aware that there is a concern. The results of this question show that half the people asked didn’t know there was an issue.

3. Reason: I wanted to find out if people were aware of the safe temperature for a bath. The results of this question show that the majority of people were not accurate. This shows that there is concern and a need for a product.

4. Reason: I asked this question to find out what potential users would like to see inputted in design.The results of this question show majority of people would prefer a led to a noise

5. Reason: I wanted to find out the quality of the materials I could use. The results of this question show people preferred a cheaper product.

6. Reason: I wanted to know if there was a real need for a temperature sensing devise that could be read easily. The results of this question show there is a need

7. Reason: I wanted to find out if there was frequent need for this product. The results of this question show there is a frequent usage.

8. Reason: I wanted to find out if people would buy one .The results of this question show that they would buy one.

Product Description – Personal Attack Alarm (£5.99) - From AmazonTiny 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 AmazonRequires 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: 85DB @ 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 AmazonKeep 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.

Examples of products for comparison (all alarms of some sort)Remember these are examples – you need to get your own

Product Comparison

All three products do the same operation (detect the temperature) but there is a range of styles and quality

Product CostTypical user

When / Where used?

FunctionTechnology

used(Input / Output)

Manufacturing process used

Digital Duck Bath Thermometer £12.99 A parent might use

it for their child.To tell the

temperature of a Childs/baby bath.

Output: LCD Screen

Input: heat

Case: Injection mouldingP.C.B.

Packaging: vacuum forming

Floating Bath Thermometer £14.94 This is for all users

adult and child

This little floating marvel will flash if your bath water is

to hot.

Output: flashing marvel

Input: heat

Case: Injection mouldingP.C.B.

Packaging: vacuum forming

Philips AVENT SCH550/20 Bath and Thermometer

£20.00 This is for all users adult and child

This floats on the bath and still

works out of water

Output: LCD Screen

Input: heat

Case: Injection mouldingP.C.B.

Packaging: vacuum forming

The Design Brief• I have found that there is in fact a gap in the market for bath temperature alarms so

I will make a devise which will solve this problem. Also there is reports of fatal injuries from burns of the water in the bath.

• I will make a heat detecting devise which will alarm the user by a red LED when the bath is too hot and when it is too cold it will use a blue LED. When the temperature is safe it will use a green LED which will be constant.

• What I need.– My circuit will need a heat detecting diode and an LED’s to warn the user if it is too hot, too cold or just

right.– .– What software you have available to you, to help you solve the problem and design a solution.

Bath Alarm for Level & Temperature£12.50 by Byreteck from Amazon

Bath Temperature & Water Level Alert Alarm£21.99 by health and care from Amazon

Function To notify the user if the water is too cold, too hot and the level too high.

To notify the user if the water is too cold, too hot and the level too high.

User need fulfilled

yes yes

Materials used in construction

Acrylic, P.C.B. and components. Acrylic, P.C.B. and components.

Durability of product

Lasts a long time but users complain its not hand held.

Very durable and a long last product.

Sustainability (6Rs)

It cant be recycled but the rest of the 6’rs apply.

This can be recycled unlike the cheaper product.

Life cycle It is good for a few month but the battery doesn’t last long enough

It is a good long lasting product

Energy use It only uses a small amount of energy

It also only uses a small amount of energy

Specification

The purpose of my product is to detect the temperature of the water and notify the user this could help if the user cant use a thermometer.My product needs to sense the water temperature and notify the user if it is too cold, too hot or just right.My product will use a thermistor to sense the heat of the water.I will use 3 different coloured L.E.D.s to notify the user if it is the right temperature.My power supply will be a pp3 battery this means it is portable. The voltage will be 9v so there is no safety hazards.My product will have an on off switch so it saves battery life.It will also have a power indicator so the user can tell if its on.The circuit will be designed in circuit wizard and will use a p.c.b.It will be manufactured using a c.a.d. program.I will ensure the circuit will work by testing it under curtain conditions.

System Diagram

Delay before INPUT

INPUTCombine inputs?

Delay after

INPUT PROCESSDelay before OUTPU

TOUTPUT

30 Water Level

Thermistor 30 s Darlington pair

30 LED

10 Thermistor Water level 10s Transistor 10 Buzzer

0 Switch none MOSFET 0 Speaker

ldr 2 comparators

0

pir Genie chip 0

0

Circuit Ideas

I like the idea of this circuit because it has all my requirements however it has a genie chip. I do not want to use this type of chip because I will have to program it and it will be more expensive.

Design (slides 12 and 13)

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.

This is my very first idea why I changed it was because I needed to adapt my circuit to the users wants ad needs. It has no manual power switch or an led to tell the user the circuit is working. Also there is only one led instead of the needed 3. however this one is a lot cheaper because of little materials used .

I used a Goldie locks circuit because it will give me the ability to have three outputs unlike an and or an or logic gate circuit. It also meets all the users needs and fits in with my questionnaire. I will not use a genie programmable chip because it is more expensive and more likely to have human error.

Circuit development

In each circuit I changed mainly the input. By adding a led to show the power is on and adding a switch so the user can turn off the power permanently. I added this because most of my questionnaire where I found out that most people wanted one.

Design (slide 14)

In my stages of development for my circuit I have managed to make my circuit smaller. I have done this to save materials and make it more sustainable. I did this because the more p.c.b. bored I save the cheaper it will be. I know the user is looking for this because I found out in my questionnaire.

Circuit ProofThis is my led to notify the user that the circuit is working and my power switch added to save power and making my circuit more sustainable.

This is showing my thermister sensing that the temperature is low and telling the user that the water is too cold by a blue L.E.D.

This is showing my thermister sensing that the temperature is average and telling the user that the water is just right by a green L.E.D.

This is showing my thermister sensing that the temperature is too hot and telling the user that the water is too hot by a red L.E.D.

I used a pp3 9V battery in order to power my circuit it is light, mobile and cheap to replace.

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 successDesign 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

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.

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.

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.

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