Article
Proximity Switch
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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.
Materials
Gerber file
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PCB
Component list
Resistors:
R1 = 10k
R2 = 4k7
R3 = 1k
R4 = 47k
R5 = 47k
P1,P2 = 100k multiturn cermet, horizontal
Capacitors:
C1,C2 = 22pF
C3 = 22µF 40V radial
C4 = 10nF
C5 = 100µF 25V radial
Semiconductors:
D1 = 1N4148
D2 = LED, red
IC1 = 4093
Miscellaneous:
BZ1 = AC buzzer
PCB, ref. 040219-1
R1 = 10k
R2 = 4k7
R3 = 1k
R4 = 47k
R5 = 47k
P1,P2 = 100k multiturn cermet, horizontal
Capacitors:
C1,C2 = 22pF
C3 = 22µF 40V radial
C4 = 10nF
C5 = 100µF 25V radial
Semiconductors:
D1 = 1N4148
D2 = LED, red
IC1 = 4093
Miscellaneous:
BZ1 = AC buzzer
PCB, ref. 040219-1
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