Hi

I have a 12v DC solidnoid ball valve to disconnect water flow, with two wires.
You have to reverse the polarity to open or close it.

I have a pair of 12v wires that when live, trigger it to open.
But what components do I need to close it ?
As when the power goes off the trigger wires the valve is still open.

Any help would be great.

Ken

 

I would use a relay with a set of double pole change over contacts, when the relay is on it opens the valve , when its de-energised it reverses the power,

if it doesn't need the power on to maintain open or closed, use a 555 timer to operate the relay.

 

A DPDT switch.

 

What signal do you want to use to operate the valve? Do you want to use a toggle switch or push-button? Can you apply continuous power to the valve?

 

The 12v DC ball valve can have continuous power.
It gets 12v trigger from a differential controller.
Which opens the valve. But when the trigger voltage stops I need the valve to shut, and therefore the valve wires have to be switched.

 

How often does the valve open and close? If not frequently, you could use a DPDT relay to perform the function. If it's frequent, you could use a transistor H-bridge.

 

Here's another idea: A double pole relay that relaxes to the "closed" condition. It would only open the valve when it gets a signal from the controller.

Wait...Dodgy Dave already said this in slightly different words,
but I did a drawing...

 

If you are manually switching it, you could just use a DPDT "centre off" switch.

 

The 12v DC ball valve can have continuous power.
It gets 12v trigger from a differential controller.
Which opens the valve. But when the trigger voltage stops I need the valve to shut, and therefore the valve wires have to be switched.

Can you give us the model number of the valve so we can see how it's used, it maybe a motorised valve?

 

This is the valve
http://www.amazon.co.uk/gp/product/B009ZCP2SE/ref=oh_details_o00_s00_i00?ie=UTF8&psc=1
I have a thermal solar pannels that heat my copper storage tank with a solar syhpon that I copied from Willis solar syphones, standing next to it which is the heat exchanger from the pannels.
I wired a differental temp controller so the pump only starts when the temp is hotter in the exchanger. The problem is at night the heat disapates back through the system. So this machanical ball valve will stop the heat loss.
I think Dodgy dave idea is good, I found this and think it will be ok.
http://www.ebay.co.uk/itm/INTERFACE...al_Components_Supplies_ET&hash=item1e70a3e64c
Do you agree and how to wire it.

 

That advertisement has no mention of the current carrying abilities of the relay contacts. However, the valve needs 1/10th of an amp, easily within the abilities of that relay.
How to wire it was given to you in post #7

One excellent feature of the valve is that it turns off its own current draw when it has completed its movement. It then waits for a reversing voltage. Very efficient to do it that way.

 

I got it all working now.
Thank you for all the help.
Ken