Intelligent Presence Simulator
Published in issue 379, July/August 2008
The circuit is very simple, as we have employed a microcontroller – a ‘little’ 12C508 from Microchip, which is more than adequate for such an application. It is mains powered and uses rudimentary voltage regulation by a zener diode. A relay is used to control the light(s); though this is less elegant than a triac solution, it does avoid any interference from the mains reaching the microcontroller, for example, during thunderstorms. We mustn’t forget this project needs to work very reliably during our absence, whatever happens.
Resistors R1 = 1kOhm 500mW R2 = 4kOhm7 R3 = 560Ohm R4,R6 = 10kOhm R5 = 7kOhm5 R 7 = LDR R8 = 470kOhm to 1 MOhm P1 = 470 kOhm potentiometer Capacitors C1 = 470µF 25V C2 = 10µF 25V C3 = 1nF5 C4 = 10nF Semiconductors D1,D2 = 1N4004 D3 = diode zener 4V7 400 mW LED1 = LED, red D4 = 1N4148 T1 = BC547 IC1 = PIC12C508, programmed, see Downloads Miscellaneous RE1 = relay, 10A contact S1 = 1-pole 3-way rotary switch F1 = fuse 100 mA TR1 = Mains transformer 2x9 V, 1.2 -3 VA 4 PCB terminal blocks, 5 mm lead pitch 5 solder pins PCB, ref. 080231-I from www.thepcbshop.com
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Please note. In view of the complexity of international markets, Elektor cannot guarantee the availability of components for this project.
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