Simple rain sensing circuit

[danrogers]

Hi all, I'm quite keen to have a go and make a rain sensing cicuit.

I have found this schematic online..

**broken link removed**

rather than have an irritating buzzer sounding I would like it to just switch on an led. What would be the best method of modifying the circuit for this purpose?

Thanks

 

[hantto]

Hi!

Just replace the buzzer with a led and one about 60ohm series resistor.

 

[magnatro]

a simpler one:

if you are a beginner.. this will help..

 

[Boncuk]

Hi Dan,

here is a circuit with less parts count and the option to decide about moist and wet.

The battery (9V) is mounted on the bottom of the PCB.

Boncuk

 

[danrogers]

Hi all, some interesting ideas there!

Bonuk, what is the function of the pot in your circuit? I guess to adjust sensitivity?

 

[magnatro]

hey bonuk, pin 7 of ICB is floating, or is this for any circuit stabilization?

 

[Boncuk]

hey bonuk, pin 7 of ICB is floating, or is this for any circuit stabilization?

Where would you connect an unused output pin?

 

[magnatro]

i will just leave it there..

 

[Reloadron]

Where would you connect an unused output pin?

To an unused input pin of course.

Ron

 

[4pyros]

Ya just use a single op amp chip. Andy

 

[Boncuk]

Hi all, some interesting ideas there!

Bonuk, what is the function of the pot in your circuit? I guess to adjust sensitivity?

Yes, it decides about the resistance of the sensor plate - completely wet or just a few drops of water on it.

Rain water doesn't have the same resistance all over the world. It has less resistance in high density industrial areas (sour rain) as is has in the jungle - hundreds of miles away from any industrial facility

Also water from a well has a different resistance from rain water.

Example: My well water has a resistance of 50KΩ/cm while rain water here has double the resistance.

Boncuk

 

[Boncuk]

Ya just use a single op amp chip. Andy

In this particular case no OpAmp, but a comparator was used. Glad if you find a single comparator with a VCC higher than 5V.

Boncuk

 

[danrogers]

thanks Boncuk!

that sounds good being able to adjust sensitivity. I think I will give that circuit a whirl. Just wondering on the best method of making the sensor without using copper as I cant see copper lasting to long out in the elements

 

[Boncuk]

thanks Boncuk!

that sounds good being able to adjust sensitivity. I think I will give that circuit a whirl. Just wondering on the best method of making the sensor without using copper as I cant see copper lasting to long out in the elements

If you tin the copper it will last pretty long. Do not use chemical tinning. It will disappear pretty soon leaving the copper which then will get a coat of "patina". Patina won't be destroyed by meteorological influence, but might increase the resistance even when wet.

You can also make a sensor of stainless steel. Just cut small stripes and connect them as shown in the picture I posted. Stainless steel can be soft soldered if you use flux for soldering.

Boncuk