D&T: Electronics and Control Systems Unit A511: Introduction to designing and making

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

2. The theme for my project isSECURITY “the state of being free from danger, damage, or worry.” Definition from Collins English dictionary

3. Why I chose security With more and more household technologies being available to the market there has been a sharp increase in what the value of goods being contained in households are and this creates an ever increasing danger of those goods being stolen and many burglars know how to get past a simple mechanical lock whereas if the lock was electronical and hooked up to an alarm it would still do the job of the lock and more. But security isn't just about keeping goods safe its also about keeping people free from worry and electronics can easily do that whether its alerting someone that their bath is about to overflow or if their child's food is too hot. Electronics can enhance security massively because in some aspects its smarter than the human mind. So I have chosen electronics because I feel it has a wide range of electronic products I can make.

4. What Could I Make? To begin to create a reliable security circuit I must first address a security problem to help me in deciding this I have created a mind map listing different problems and listing possible circuits to address the problem The problem I have decided to solve the problem of household safety, specifically child safety around the bath by creating a bath temperature alarm.

5. Brainstorm and investigate your users, your place and other products like your intended product. Usersneeds What is the problem? My user will want my device to alert them when their child’s bath water has become dangerously hot. When will my user need it to work? My user will need it to work when the bath water for their child has become too hot. Where will my user use this product? My user will use my product in their bath. USERS NEEDS Who is my products intended user? My products intended user is a parent that has a child who is old enough to use a regular bath but still need supervision when around a bath Why does my user need this product? My user needs this product to ensure their child's safety while in the bath

6. Evidence Newspaper article taken from the “empire gazette”. An 8-month-old baby has been taken to Children’s Mercy Hospital in Kansas City for treatment of burns received while receiving a bath. According to the Lyon County Sheriff’s log, the baby’s 11-year-old sister was preparing to bathe the boy and forgot to add cold water to the bath. He was taken to Newman Regional Health and transferred to Children’s Mercy with second-degree burns. He was in fair condition this morning. This evidence leads me to believe that my intended user would be the person in charge of supervising a young child around the bath. Taken from the BBC news website This evidence proves that babies and young children are all at risk around a hot bath. This also proves that my product should be intended to keep children under three safe from harm Every day 10 children receive serious burns from hot bath water, a total of 3,500 each year. Two children die each year as a result of injuries caused by very hot bath-water. Many children under three suffer 20 to 50% body burns. Extensive plastic surgery is common. If this household did own a bath temperature alarm then the 11-year old sister would have known the water was too hot and it would have stopped this child from receiving burns. this cartoon illustrates that my temperature alarm would be used in the bath. This is a picture of my intended user. a parent that has a child who is old enough to use a regular bath but still needs supervision when around a bath

7. This is the questioner I got people from my local area to fill out. Before I got them to fill it out I explained what my intended product was. Each question helps me to understand who, what, when and where. Before asking them these questions I made sure they had a child between the age of 8-22 months. Questions 1,5,6 and 9 help me to understand what problem my device should address and what specifications it must have. Questions 3,4,5,7 and 8 help me to understand who my intended users are and whether they would use it. Question 1 and10 help me to understand where my product will be used. Question 4 helps me to understand when my product will be used.

8. Questionnaireresults The results from my questionnaire have told me that: • There is a need for my product because there are a number of parents are aware of the dangers of the bath and are worried about it. • Most parents don’t currently have a way of judging the temperature of the bath water other than their own judgement. • Those parents that are worried about their child's bath would be willing to buy my supposed product and use it every time their child is in the bath and that most parents would feel confident using it. • The parents would want an alarm feature to alert them when it is too dangerous for the baby to enter the bath. • My product would have to stand out as it would be competing with other devices that parents are familiar with on the market. • It would be bought by many parents as it would have been mentioned to them by other parents proving there could be a market with such a product.

9. Comparison of products related to my theme Texecom AEC-0001 Impaq Glass Break Detector König Wireless Alarm with Motion Detector Friedland Response SL1 Home and Away Wirefree Burglar Alarm System

10. Comparison review The trend identified by the table on the previous slide shows that the higher the price the more complicated the system, for example, the “Texecom AEC-0001 Impaq Glass Break Detector” is the cheapest and is a simple device which only requires the user to install and turn it on, and is made from cheap materials. Whereas the “Friedland Response SL1 Home and Away Wirefree Burglar Alarm System” is the most expensive and complex and not only requires the user to install and turn it on but also to arm it and set preset codes to reset the alarm, it is also more versatile as it can adapt to use more inputs, it is also made to last by using more expensive materials ensuring the customers gets their monies worth.

11. More detailed comparison The Texecom Impaq Glass Break provides protection from an intruder coming through the window. The Impaq Glass Break is an acoustic glass break detector designed to provide warning of a potential intruder by detecting the sound of breaking glass. An advanced microprocessor processes information about the frequency, amplitude and timing of every sound. The Impaq Glass Break can be set to either Plate and Tempered or Laminated and Wired glass types. Dual green and red LEDs indicate pre-alarm signals. The Impaq Glass Break can be mounted on walls, in corners or on the ceiling. Wireless alarm with motion detection and remote alarm. Also suitable as door chime. Easy to operate and a quick installation without any wiring. Pre-programmed exit and entry delay. Perfect for securing any room or area. When it detects infrared-movement it sounds a 90db alarm . An alarm system that has individual control access. Ideal for small homes or for use by the elderly and children as there are no access codes to remember. Solar siren uses daylight to maintain battery charge – reduces the need to buy expensive non-chargeable batteries. Once it detects an intruder through a door or window it sounds a 95db alarm

12. Design brief Judging by the evidence I have collected I have come to the conclusion that there is a need for my product idea of a bath temperature alarm. The evidence I have collected tells me that there is a definite risk of a child being burned in a dangerously hot bath. The majority of the people who worry about this health risk are parents who have children who use a regular bath but need constant supervision around a bath. Using this conclusion my design will have to be a reliable way of alerting the user that their child’s bath water is dangerously hot or cold. Its input will have to be a thermal sensor that will be set to a specific temperature. The output could be some sort of visual indication of the temperature of the bath, propably LED based. my next step should be to find suitable circuits that match this design brief. I already know that the circuit I chose shouldn’t include a 555 latch switch as it is not suitable to a bath temperature alarm. To build my circuit I am using a block method where I amusing pre built component blocks to aid design and building my circuit. The resources I have: • Circuit wizard • Websites that specialize in circuit ideas • School recourses

13. Product analysis Baby bath water Thermometer Bath Temperature & Water Level Alert Alarm The baby bath water temperature alarm feature a wireless thermometer connected to central hub which give more detailed data. Feature a temperature sensor with a high/low alarm feature. Sets off alarm if water is outside pre-set temperature. The Bath Level and Temperature thermometer can be used in the bathroom where care is required. It shows the water temperature with high/low alert feature. The Bath Level and Temperature Alert Alarm also includes a water overflow alarm system. Digital temperature display. Alarms if water temperature outside pre-set level.

15. specification The purpose of my proposed product will be to alarm parents when their babies bath has become dangerously hot or cold, this to allow parents to feel that their babies bath is safe. My proposed product will need to sense the temperature of the bath water this is to determine whether the bath water is safe for a baby as many people agree the bath can be a dangerous place My proposed product will need to have a system of informing parents about the temperature of the bath, possibly and LED system as parents agreed that was a good idea. The power supply for my proposed product will need to be a 9v pp3 battery because that is the safest power source I can use for my proposed product also my product will need to be portable because using the mains around the bath would be dangerous and unpractical. My proposed product will run on 9v as that is what the power source will give out. My proposed circuit will not have an on/off switch this is to avoid the safety risk of forgetting to turn it on. My product will be designed using current products on the market to create a reliable product similar to those on the market. My proposed product will be manufactured by using computer aided design software to create the right size PCB board and then I will individually place and solder each component to the board this is to manufacture my product accurately and efficiently.

16. I know that I am designing a Bath Temperature alarm designed for small children. I know the input will have to be a temperature sensor however I need to consider what other features I could use within my circuit, I know the output must be obvious to alert the parents as to whether there babies bath is dangerous.

17. 4 circuit ideas Here are 4 circuit ideas I have found on the internet to base ideas for my circuits final production. Each one contains a description and a box diagram. When the resistance from the thermistor is low enough it forces the current through the transistor to the buzzer, this circuit is a very basic representation of what my interpretation of what my intended circuit is to be so I will not be considering this circuit for final production

18. In this circuit instead of a resistor there is a Darlington pair connected so when the resistance from the thermistor is low enough it forces the current through the Darlington pair towards the buzzer. Again this circuit is a very basic representation of what my intended circuit is to be and again I will not consider this for final production

19. In this circuit when the resistance form the thermistor is low enough it forces current to the thyristor towards the buzzer but then it recycles the current towards the buzzer until the circuit is reset using the switch. This circuit, like the ones before, is again a very basic representation including to much from my design brief so I will not consider it for final production.

20. In this circuit there are comparators to drive the large amount of outputs happening. When the resistance from the thermistor is low enough it forces current to the right comparator and then it sends the current towards the right LED. This is a very good representation of what I intend for my final circuit to be as it contains everything included in my design brief, because of this, this design will be considered for final production.

21. Development of circuit The 1st design: This as my original design of a simple heat detection. The led would turn on when it was too hot. When the resistance from the thermistor is low enough it forces the current through transistor towards the LED.

22. The 2nd design: This design was a little more complex as it incorporated 2 LED’s to indicate what the temperature was, either hot or not. When the resistance form the thermistor is low enough it forces current through the comparator and towards the positive LED. However when this is not happening current is forced through the negative LED.

23. The 3rd design: This design was almost identical to the previous one but this design incorporated a power indicator. When the resistance form the thermistor is high enough it forces current through the comparator and towards the positive LED. However when this is not happening current is forced through the negative LED.

24. The final design: This was my final design. I had gotten rid of the power indicator as I realised that the LED’s already told the user whether or not it was on. It has three LED’s to tell whether its too hot, just right or too cold. It is two of the above circuits combined. The variable resistors can be used to adjust the temperature at which LED will turn on. When the resistance form the thermistor is low enough it forces current through the comparator and towards the red LED(too hot). However when this is not happening current is forced through the blue LED(too cold). How ever also in this circuit is a set “in the middle temperature” at which a green LED will be switched on(just right).

25. Test table

26. PCB design: I had to go through over 4 different designs before arranging my components in a practical way that still allows the circuit to function. I have tested each step to ensure the circuit works all the way through. I first had to ensure all routes were connected by ensuring there was no blue and green wires. I had to also adjust the tracks and certain pad sizes to ensure that my circuit did not produce as much waste and have an environmental impact and also for neatness.

28. Final PCB design Battery (9v) Comparator resistors Thermistor LED’s Variable Resistors

30. Testing Plan

32. Here is my PCB board ready for the components to be soldered on too. After designing my PCB mask on circuit wizard I used a band saw to size my board, after doing this I then exposed it to UV light after being exposed it was then developed using development fluid which was then etch using etchant once this was finished the holes were then drilled into the PCB after having tiny holes to centre the drill. Here is my PCB board and the printout of my circuit to ensure I solder the correct components in the right place. By doing this I ensured that there could be no error in the production of my PCB, as you can see the printout is orientated in the same way as my board to ensure I understand where each component should go. Here is my PCB board and my resistors, the first of my components to be soldered onto the board. As you can see to solder something correctly you must first place the solder around the joint you wish to secure then apply the hot tip of the soldering iron to the solder ensuring a small blob is around the joint with no gaps, by doing this you ensure the joint is secured correctly.

33. Here is a mistake a made, I have soldered two chip pins together if left uncorrected this could cause serious problems for my circuit and could potentially blow the chip which could be a serious health hazard, there are several tools that could correct this mistake, the first would be a solder sucker which sucks melted solder off the PCB, the next is a copper wire which when heated will remove the solder as it sticks to it when melted. Here is the correction of the mistake I made, by separating those two pins that were connected, I used a combination of the solder sucker to get most of it out I then used a copper wire to get the rest, I then had to re-solder the joint correctly. Here is my complete circuit, as you can see all my off board components are soldered on, 3 LEDs, thermistor, slider switch and a battery clip, each off board component is soldered and then a small section of plastic tube is place around exposed wire, when heat is applied to this plastic it shrinks, forming a seal on these expose wires.

34. For the purposes of this demonstration, although my test says the thermistor should be placed in water to simulate temperature change, I have used a can of deodorant to simulate temperature change.

35. Testing Plan

37. Improvements • What could I have done differently: • One improvement could be to decrease the amount wasted by bringing my components closer together. • I could have designed the circuit differently and instead of using an LED system I could have used an alarm to indicate when the bath was dangerously cold or dangerously hot although this circuit would not be as user friendly as my current design.