About the article

Waterproof Bathroom Switch

(Summer Circuits 2010 article)

Waterproof Bathroom Switch

The object of this circuit is turn the domestic lighting on and off in complete safety in a room with very high humidity. A detector, flush-mounted into the wall, detects the magnetic field variations caused by the proximity of a hand and controls an AC power switching system. Hence lighting control is achieved through the wall covering, with no exposed electrical equipment.

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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.

Resistors (SMD 1206, 125 mW)
R1 = 470 kOhm
R2 = 4.7 kOhm
R3 = 1 kOhm
R4, R5 = 390 Ohm
Rx = see text

C1 = 47 µF / 16 V (diam. 6.3 mm)
C2, C4 = 100 nF (SMD 1206)
C3 = 2.2 µF / 10 V (SMD-A)
C5 = 3.3 nF (SMD 1206)
Cx = see text (SMD 1206)

D1,D2 = 1N4148 (SMD MELF)
IC1 = LP3985IM5-3.3/NOPB (SMD SOT23)
IC2 = ATtiny13A-SH (SMD SOIC8)
T1 = BC848BLT1G (SMD SOT23)
TRI1 = T835-600G (SMD D2PAK)

TR1 = power transformer 2 x 6 V / 0.175 VA VB0.35/3/6
F1 = fuse 250V (115V) / 1A slow blow, with holder
K1 = 3-way PCB terminal block, lead pitch 0.3 in. (7.5mm)
K2 = 6-pin (2x3) pinheader, lead pitch 0.1 in. (2.54mm)
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