Rain Detector

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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 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.

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Comments

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anonymous Rain Detector Thursday, February 16, 2012 10:09:26 PM

change the scr with a bjt NPN transistor

anonymous Rain Detector Wednesday, December 21, 2011 10:16:39 AM

Why doesn't OFF when it drys?. Very simple: change The DC supply for an AC supply; the SCR turns OFF during the power supply's negative cycle . Additionally, you can change the SCR for a TRIAC.

anonymous Rain Detector Tuesday, December 13, 2011 9:37:09 PM

If it detects rain, and when it drys it still thinks there's rain probably you could put 1N4148 instead of 1N4001 because 1N4148 is a fast recovery diode... maybe...

Drikus Rain Detector Sunday, November 06, 2011 3:20:17 AM

hey. Is this parts also available in south africa? Lol.. sorry but I would like to know

anonymous Rain Detector Saturday, March 05, 2011 12:01:38 AM

SIR, can you explain the function of each part of the circuit, especially the diode and the resistor.

ubed ullah khan lohani Rain Detector (to stop the buzzer) Monday, August 16, 2010 10:02:46 PM

to stop the buzzer you have to replace the SCR with a BJT in darlington pair arrangement... and also use 10k resistance as R1 connected with gate.. and the collector of transistor with the buzzer's leg. and emitter =>ground.........BJT 547 will be sufficient for that.

anonymous Rain Detector Sunday, July 11, 2010 4:17:01 AM

i have maid one, its perfect! i just follow the schematic and it works.

anonymous Rain Detector Monday, June 21, 2010 6:19:44 AM

Is it really not switching off when the sensor is dry?

anonymous Rain Detector Tuesday, December 01, 2009 3:40:41 AM

i built this project, but the "buzzer" still On after sensor become wet, but after the sensor is dry, the buzzer still active, Why??, I want the sensor to stop the buzzer when dry. thanx

Questioner Rain Detector Saturday, September 05, 2009 2:38:01 PM

How to make the circuit can differentiate between light, moderate and heavy rain? The application is to control speed motor. For example, minimum speed for light rain and maximum speed for heavy rain.

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anonymous	Rain Detector	Thursday, February 16, 2012 10:09:26 PM
change the scr with a bjt NPN transistor
anonymous	Rain Detector	Wednesday, December 21, 2011 10:16:39 AM
Why doesn't OFF when it drys?. Very simple: change The DC supply for an AC supply; the SCR turns OFF during the power supply's negative cycle . Additionally, you can change the SCR for a TRIAC.
anonymous	Rain Detector	Tuesday, December 13, 2011 9:37:09 PM
If it detects rain, and when it drys it still thinks there's rain probably you could put 1N4148 instead of 1N4001 because 1N4148 is a fast recovery diode... maybe...
Drikus	Rain Detector	Sunday, November 06, 2011 3:20:17 AM
hey. Is this parts also available in south africa? Lol.. sorry but I would like to know
anonymous	Rain Detector	Saturday, March 05, 2011 12:01:38 AM
SIR, can you explain the function of each part of the circuit, especially the diode and the resistor.
ubed ullah khan lohani	Rain Detector (to stop the buzzer)	Monday, August 16, 2010 10:02:46 PM
to stop the buzzer you have to replace the SCR with a BJT in darlington pair arrangement... and also use 10k resistance as R1 connected with gate.. and the collector of transistor with the buzzer's leg. and emitter =>ground.........BJT 547 will be sufficient for that.
anonymous	Rain Detector	Sunday, July 11, 2010 4:17:01 AM
i have maid one, its perfect! i just follow the schematic and it works.
anonymous	Rain Detector	Monday, June 21, 2010 6:19:44 AM
Is it really not switching off when the sensor is dry?
anonymous	Rain Detector	Tuesday, December 01, 2009 3:40:41 AM
i built this project, but the "buzzer" still On after sensor become wet, but after the sensor is dry, the buzzer still active, Why??, I want the sensor to stop the buzzer when dry. thanx
Questioner	Rain Detector	Saturday, September 05, 2009 2:38:01 PM
How to make the circuit can differentiate between light, moderate and heavy rain? The application is to control speed motor. For example, minimum speed for light rain and maximum speed for heavy rain.