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Twilight Switch

Twilight Switch
Nowadays, you do not actually need to build twilight switches yourself, since they can be purchased quite inexpensively. However, if you enjoy doing so and you perhaps already have the parts on hand (cannibalised from a readymade unit?), then who’s to stop you? In addition, if you do it yourself you have the unique opportunity to make something that exactly matches your own taste and wishes.Building a twilight switch is certainly not difficult, as is illustrated by the design presented here. It uses the well-known 555 IC (here in the economical CMOS version), which has a trigger input with hysteresis (‘on’ at 2/3 of the supply voltage, ‘off’ at 1/3) and an internal flip-flop as a memory element.
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor Members can exclusively download these files for free as part of their Membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service. Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

R1 = LDR
R2 = S10K250 varistor
R3,R4 = 470Ohm
R5 = 10Ohm 1W
P1 = 100 k preset H
C1 = 100nF
C2 = 100µF 16 V radial
C3 = 470nF 250VAC, class X2
C4 = 470µF 16V radial
D1,D3 = zener diode 12V 1W
D2,D4 = 1N4004
D5 = 1N4001
IC1 = 555C
Re1 = 12-V-relay, e.g., Siemens V23057-A2-A101
K1,K2 = 2-way PCB terminal block, lead pitch 7.5 mm
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