Daylight Switch
Published in issue 391, July/August 2009
This project was originally designed for lighting up an illuminated sign for a wine-grower. The sign was originally controlled by a simple time-switch, which had to be reprogrammed every day to avoid the sign's lighting up while it was still daylight. This is time-consuming, and can lead to wastage of electricity and other resources. A better solution would be an automatic switch capable of detecting the transition between daylight and night-time.
Resistors R1 = 47Ohm 1W R2 = 470kOhm R3 = LDR R4, R5 = 100kOhm R6 =1kOhm P1 = 1MOhm multiturn preset, vertical Capacitors C1 = 1µF5 400V MKT C2 = 1000µF 25V axial C3 = 100nF LCC 63V C4 = 10µF 25V radial Semiconductors D1–D4, 6 = 1N4007 D5 = 15V 1.3W zener diode T1 = BC547 or equivalent IC1 = µA741 or equivalent IC2 = 7812, or low-drop equivalent Miscellaneous RE1 = relay, 12V coil, 1x 10A, 250V c/o contact K1,K2,K3 = 2-way PCB terminal block, 5mm (0.2") lead pitch Type IP55 electricity junction box, internal dimensions 80 x 80 mm (3.15" x 3.15") e.g. plexo LEGRAND # 922-06 20 mm length of electricity conduit, diam. 20 mm (0.8")
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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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