Automated Water Mister (closed circuit soleniod switched off)

[Richardegrant]

Hi everyone this is my first time here, I know what I want to make but cant get my head around the reverse operational action I require.Yes my electronic knowledge is poor I'm more of a mechanical and engineering person. If someone could give me some guidance I would really be grateful.

I want to create a propagating misting system for the greenhouse but I want the soleniod to be turned of when the moisture sensor senses moisture. So when the plants leaf surface ( Moisture sensor) dries out the mister is switch on to cover the leaf with moisture. So I want the system to continuously keep the leaf surfaces moist. Please see my crude diagram attached

Cheers

Richard

 

[Minder]

How is your electronic ability?
What is the nature of the signal out of the Moisture sensor?
A couple of ways, one is with a LM311 comparitor and a SSR to operate the solenoid if it is a AC solenoid.
More info on the sensor and solenoid would be useful.
M.

 

[Braeden Hamson]

I found a soil moisture sensor.
https://www.sparkfun.com/products/13322
It could be wrapped in cotton or something to act like a leaf. It outputs a varying voltage based on moisture. Minder mentioned a voltage comparitor, it think theyd pair well.

 

[Alec_t]

What is the voltage/current rating of the solenoid valve?

Edit: If using that particular soil sensor, this document says it needs a 3.3V-5V supply but it shouldn't be continuously powered.

 

[Braeden Hamson]

What is the voltage/current rating of the solenoid valve?

Edit: If using that particular soil sensor, this document says it needs a 3.3V-5V supply but it shouldn't be continuously powered.

Excellent catch, I imagine that's because of electrically accelerated corrosion?

 

[AnalogKid]

What is the manufacturer/part number/web page for the sensor?
What power is available for the monitor circuit?
What is the manufacturer/part number/web page for the solenoid?
Can you post datasheets for the sensor and solenoid?

ak

 

[Richardegrant]

Hi thanks for your replies, the soleniod uses 9v and is 0.6mA, sensor is going to be a simple piece of circuit board cut into like the pattern in my diagram to create 2 separate areas connected to by the 2 wires to be shorted ie closed circuit to trigger the switching off of the soleniod. Im thinking I need a NOT gate transistor circuit?

 

[AnalogKid]

Hi thanks for your replies, the soleniod uses 9v and is 0.6mA,

???

ak

 

[AnalogKid]

sensor is going to be a simple piece of circuit board cut into like the pattern in my diagram to create 2 separate areas connected to by the 2 wires to be shorted ie closed circuit to trigger the switching off of the soleniod.

That is a *very* high impedance sensor. Also, it will continue to conduct until the water on it has evaporated. And, the salts and other goop left behind by many evaporation cycles will form a permanent conductive path.

ak

 

[Richardegrant]

okay thanks for the advice what do you recommend as an alternative?

 

[Alec_t]

the soleniod uses 9v and is 0.6mA

Do you mean 0.6 AMPS?