solenoid control

Discussion in 'The Projects Forum' started by samjesse, Jul 24, 2012.

  1. samjesse

    Thread Starter Senior Member

    Sep 14, 2008

    I have a 15w 12vdc solenoid, which I need to either turn on or off approx. 2 seconds cycle between off/on for some time.
    I am envisioning a 3 position switch I can hold in one hand with wires coming out of it. With my thump I can move the switch to either the Off, Cycle or On position, and then a pot. Lever next to the button to adjust the cycling time of a 555 chip when the switch is on the Cycle position.

    Can I find such a switch and would the 555 do it?

    Many thx
  2. mcasale


    Jul 18, 2011
    Switches like you describe are common. You can probably get it at Radio Shack or at an online distributor. The 555 can easily handle the timing. I suggest you google for sample circuits. However, you will need a driver to handle the current through the solenoid (over 1 amp) and be sure to add a flyback diode to protect against turn off voltage spikes.
  3. samjesse

    Thread Starter Senior Member

    Sep 14, 2008
    I was able to find SP3T single-pole, triple-throw switches but can not locate one with a built in pot. slider where all can be thump operated in one hand.
    Last edited: Jul 24, 2012
  4. cork_ie

    Active Member

    Oct 8, 2011
    You could use a potentiometer,with zener clipping circuits at either end , i.e. a minimum threshold voltage from the pot wiper below which nothing would happen and a maximum threshold voltage from the pot wiper beyond which a relay or power transistor would be driven full on. Between these two parameters you could allow the timer circuit to take control.
    By the way your solenoid is drawing 1.25A and while that is no problem for a power transistor you are going to have a fairly hefty voltage spike every time the solenoid is de-energised. I would suggest that you use a small slave relay to drive the solenoid with a 0.1μF 200V capacitor across the relay contacts.