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.

Circuit diagram

Rain Detector-Circuit diagram


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


  • 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.
  • Make sure to use a loud buzzer.