Wednesday, July 13, 2011

Rain Detector

This circuit uses a sensor made of a small piece of etched PC board and a simple SCR circuit to detect rain and sound a buzzer. The SCR could also be used to activate a relay, turn on a lamp, or send a signal to a security system.


R1(1)1K 1/4 W Resistor
R2(1)680 Ohm 1/4 W Resistor
D1(1)1N4001 Silicon Diode
BZ1(1)12V Buzzer
S1(1)SPST Switch
SCR1(1)C106B1 SCR 106CY
SENSOR(1)See Notes
MISC(1)Board, Wire, Case, PC Board (For Sensor)


  1. The sensor is a small piece of PC board etched to the pattern showen in the schematic. The traces should be very close to each other, but never touching. A large spiral pattern would also work.

  2. Make sure to use a loud buzzer.

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