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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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.

Julian Rain Detector Saturday, May 09, 2009 4:19:17 AM

I've built this but it activates even when i complete the circuit with two people touching hands in series with the detector. Its WAY too sensitive. Is there a resistor change that would make the detector less sensitive? It also doesn't turn off when the contact across the sensor (water or finger) is removed. HELP

anonymous Rain Detector Sunday, March 15, 2009 7:21:58 PM

fantastic i have my own idea for this and let you know when i sort it ;) thanks

M. ASlani Rain Detector Sunday, March 08, 2009 2:24:57 PM

There is a problem with this rain sensor. the rain drops remain on the surface of sensor even when the PCB is installed in 45 degree position. Does somebody suggest any method to solve this problem?
(Editor's notes: Coat with RainX.)

conductivitysensor Rain Detector Wednesday, February 18, 2009 9:30:54 AM

does this pc board works if u plant it in the soil and can detect conductivity if you will water the soil??

siddeswaran Rain Detector Monday, February 16, 2009 2:42:28 AM

when the water falls on the sensor it sense , transfer the information to scr1 and to activity the buzzer

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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.
Julian	Rain Detector	Saturday, May 09, 2009 4:19:17 AM
I've built this but it activates even when i complete the circuit with two people touching hands in series with the detector. Its WAY too sensitive. Is there a resistor change that would make the detector less sensitive? It also doesn't turn off when the contact across the sensor (water or finger) is removed. HELP
anonymous	Rain Detector	Sunday, March 15, 2009 7:21:58 PM
fantastic i have my own idea for this and let you know when i sort it ;) thanks
M. ASlani	Rain Detector	Sunday, March 08, 2009 2:24:57 PM
There is a problem with this rain sensor. the rain drops remain on the surface of sensor even when the PCB is installed in 45 degree position. Does somebody suggest any method to solve this problem? (Editor's notes: Coat with RainX.)
conductivitysensor	Rain Detector	Wednesday, February 18, 2009 9:30:54 AM
does this pc board works if u plant it in the soil and can detect conductivity if you will water the soil??
siddeswaran	Rain Detector	Monday, February 16, 2009 2:42:28 AM
when the water falls on the sensor it sense , transfer the information to scr1 and to activity the buzzer