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.
Schematic
Parts
Part
Total Qty.
Description
Substitutions
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)
Notes
The sensor is a small piece of PC board
etched to the pattern shown in the schematic. The traces
should be very close to each other, but never touching.
A large spiral pattern would also work.