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# How to control a solenoid? Answered

Hi,
I have a tiny solenoid from an automatic air freshener that I want to control manually.
The solenoid acts as a valve that opens when fed 5v, and closed when no voltage is present.
On the factory board, there's a timer that triggers the solenoid every few minutes for a fraction of a second (opens and closes so fast it just sounds like a click).

What is the simplest way (No Arduino, Raspberry, etc.) to make a 5 volt pulse to make it go "click" on the push of a button?  Further more, how would I control the length of the 5v pulse?  I want to be able to control the amount of gas it passes (Pun intended) when activated.

Any information would be helpful, and a circuit diagram would be greatly appreciated (I can read diagrams but can't design a circuit).
Thanks!!!

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## 7 Replies

Try this one

Morgantao (author)2013-11-22

Perfect.
Thanks for the help guys!

steveastrouk (author)2013-11-21

Look for circuits like this

Morgantao (author)2013-11-22

Perfect!
You're amazing dude. :)

Morgantao (author)2013-11-21

That is ALMOST what I need....
Alas, the circuit in the link has adjustable frequency AND adjustable pulse width. I need just a variable pulse width with no frequency at all (One pulse per push of a button).

I'm sure it's a simple conversion from the linked circuit to what I need, but I wouldn't know where to start :(

I'll google some more, see if I can find something along these lines.

steveastrouk (author)2013-11-21

In that case this is all you need. A 555 "one-shot" or "monostable"
http://www.technologystudent.com/elec1/5554.htm

Morgantao (author)2013-11-21

Ah, that's more like it :)
Just a couple of questions:
1) What happens if the activation button is held for longer than the timer cycle? In the linked example, the buzzer sounds for 8 seconds, but in my application we're talking about fractions of a second. Will the circuit "rapid fire" like a machine gun, or will it act like a pistol (One pull of the trigger equals one shot, no matter how long you keep the trigger pulled)?
2) On the last sentence of the last paragraph they talk about VR1. I don't see it in the diagram. Do they mean I replace R1 with a VR?