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Unit A511: Introduction to designing and making. D&T: Electronics and Control Systems. Name: Alexander Lloyd Candidate Number: 9177 Centre Number: 16527. The Theme.
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Unit A511: Introduction to designing and making D&T: Electronics and Control Systems 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 A rap alarm is made and when the button is pressed, a large siren is sounded for five minutes A rap alarm is made and when the button is pressed, a latched large siren is sounded The Theme Two pressure plates are triggered and then a large sounding siren Burglar gets in because their is no security in the home Sexual Assault An alarm is sounded when the room gets below a set temperature House Burglary A woman is attacked and not have a way of deterring the criminal A keypad lock is fitted to the door and if an incorrect combination is inputted, then an alarm goes off Burglary An elderly person falls asleep and then gets too cold and dies of Hypothermia. Security Easy to break in because their is no security and lots of valuable items in it. Shed Burglary Elderly person A set of LEDs indicate the temperature and if below a buzzer is sounded Temper-ature of a bath A CO2 detector detects that the burglar is present and a large siren is sounded A thermistor probe is placed in the water and if too hot a red led is lit A baby is placed in a bath that is too hot and then causes bad burns on the baby The highlighted boxes shows the choice I decided to made for my product
This is me conducting a questionnaire about this project User Needs The newspaper clipping shows that their are burglaries in the local area. In the clipping, their was luckily nothing stolen. It happened during the nightConclusionThe 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 where most burglariesoccur. 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. Statistics showing Burglaries on the rise This is an article of a burglary in the local area A burglar in the act of Burglary
The Questionnaire The results of my questionnaire: 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 Light Sensor Light Motion Sensor Reed Switch Alarm Key Pad
Trend of product ComparisonThe 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 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.
System Diagram 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. 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.
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. 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.
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.
Development of the chosen circuit I added a power indicator so the user knows it is on. 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 four PCBs below are the developmentwhile the PCB to the right is one that does not work because it tracks overlapped. The PCB 2. 1. 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 is my final circuit. Here I continued to move the components and was able to remove all but two blue wires.
Wire Cutters Tools 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 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. 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. Soldering Iron Small Nosed Pliers are used to bend resistor or capacitor wires so that it is easier to solder to the board. They also allow you to hold the components while soldering so you don't burn yourself. Small Nosed Pliers Wire Strippers 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. Multi Meter The multi-meter allows the user 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. Heat Gun The heat gun is used to heat the heat-shrink rubber to the wire and off board components. This makes the components and wire less likely to break.
Manufacturing the circuit, the PCB First the PCB has to be printed on glossy flexible transparent plastic. A laser printer will need to be used because laser ink does not dissolve in the etching fluid. The Ink protect the copper to make the tracks. 4. 1. Place the treated board into the etching tank, this is a very difficult part because if over developed, then the board may be unusable. Stick the PCB to a pre-cut to size the Copper clad. The copper must be the same size as the print out border of the PCB. It may have a protective plastic over the photo-resistant, if so then take it off and go on to the next step 5. Drill the holes for the PCB. This is done by using a 1mm drill bit in a small pillar drill. Align the drill with the where you want to drill the hole. Then with the board held tightly push the pillar drill into where you want the hole. Note that some components such as variable resistors will need bigger holes. The PCB is now ready for soldering components on. 2. 3. Place the Copper clad and Printed out PCB in the ultraviolet light where this will cause a chemical change to the unprotected copper 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. 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 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. 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. 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. 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
Manufacturing the Circuit, the soldering Now I soldered the off board components to the board. I started with the PIR, then the Light dependant resistor, bulb wires, LED, switch and lastly battery. I looked at a picture of the circuit printed off circuit wizard so that I knew the right way to place polarised components such as the PIR and battery. Then the NAND gate and 555 timer chips were placed in the appropriate chip socket. This had to be placed carefully because the chip pins could bend and the chip may be unusable. Also your static may damage your chip. The chip socket was soldered next. I soldered the notch in the same way as the chip notch. This is because the chip will not fit in if the sockets not in the right way. The MOSFET was then soldered in with no problems. It has too be placed in the right way because it is polarised. If placed in the wrong way, then the MOSFET would get damaged and the circuit will not work. When testing the circuit, I noticed that the bulb was alit a little. I then realised that the battery was wired the wrong way round. This occurred because the red and black 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
Manufacturing and Functional Evaluation Manufacturing Functional • 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. • 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. • 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. • 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.
