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Proximity Switch


Proximity Switch
This circuit is for an unusually sensitive and stable proximity alarm which may be built at very low cost. If the negative terminal is grounded, it will detect the presence of a hand at more than 200mm. If it is not grounded, this range is reduced to about one-third. The Proximity Switch emits a loud, falling siren when a body is detected within its range.
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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 = 10k
R2 = 4k7
R3 = 1k
R4 = 47k
R5 = 47k
P1,P2 = 100k multiturn cermet, horizontal
C1,C2 = 22pF
C3 = 22µF 40V radial
C4 = 10nF
C5 = 100µF 25V radial
D1 = 1N4148
D2 = LED, red
IC1 = 4093
BZ1 = AC buzzer
PCB, ref. 040219-1
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