Waterproof Bathroom Switch
(Summer Circuits 2010 article)
Published in issue 403, July/August 2010
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. Resistors (SMD 1206, 125 mW)
R1 = 470 kOhm
R2 = 4.7 kOhm
R3 = 1 kOhm
R4, R5 = 390 Ohm
Rx = see text
Capacitors
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)
Semiconductors
D1,D2 = 1N4148 (SMD MELF)
IC1 = LP3985IM5-3.3/NOPB (SMD SOT23)
IC2 = ATtiny13A-SH (SMD SOIC8)
IC3 = QT113A-ISG (SMD SOIC8)
IC4 = S2S4BY0F (SMD SOIC4)
T1 = BC848BLT1G (SMD SOT23)
TRI1 = T835-600G (SMD D2PAK)
Miscellaneous
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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Click below to download a PDF copy of this article from Elektor magazine. Please note. In view of the complexity of international markets, Elektor cannot guarantee the availability of components for this project.
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