These are the tasks and dates of my project; Introduction to project (1) 18th December Introduction to project (2) and issue of planning form 8th January. Plan project between 10th January & 7th February. Hand in planning form and order components 7th February. Practical work 18th February to 21st March Project photographed 21st March Report by 9th April Timescale; Design and research layout: 1 hour lesson. Assembling & testing first sub-system: 2 hour lesson. Assembling & testing subsequent sub-systems: 2 hours per sub-system. Dates;
> Completion and evaluation of complete circuit: 19th March > Completed report: 8th April Specification: Aim; My aim is to design and build a doorbell for the deaf. When the circuit detects movement, it switches on a light, which stays on for a certain amount of time. Complete description; The first part of the circuit, before the sub-system, is a simple switching device using a transistor. The sub-system compares the voltage from the next part of the circuit, to the first part of the circuit. The last part of the circuit monitors the output from the LDR.
And the final part is the LDR and potentiometer (Light Dependent Resistor) whose resistance increase with light. Testing the circuit; I tested the resistance that I would receive from the LDR when it was totally dark (810? ), and when it was light (50k? ). I tested the potentiometer so that I knew what voltage that was flowing through it. It ranged from 1. 65volts to 5. 5 volts. I tested the sub-system to make sure its truth table, was what this particular chip was acting like. I also tested capacitors to see if what the best time for the LED to stay on was.
Building: Diary; 1. In the first week I started to build the first part of the circuit, trying to colour code the wires coming from the positive power rail (red wire), the negative power rail (black wire), and linking components (yellow wire). 2. In the second week I concentrated on the building the sub-system, and testing to make sure its truth table, was what this particular chip was acting like. 3. In the third and final week I finished building the last part of the circuit and making sure it worked. Tests; LDR; Light Intensity Resistance 1 (? ) Resistance 2 (?) Average Resistance (? ).
Dark 800 820 810 Dusk 22. 7k 26. 7k 24. 2k Light 49. 6k 50. 4k 50k Capacitor Attached, as appendix 1, is the graph of the discharge of a capacitor. Evaluation; My final circuit meets the specification because the LED stays on for 13 seconds when the LDR detects some one is at the door. It is reliable. Show preview only The above preview is unformatted text This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section. Download this essay Print Save Not the one?