A double acting solenoid and a PLC

I'm going to connect a double acting solenoid valve to a plc ... In one of the forums I read that the double acting SV does not have an initial position and when deactivated it stays at the position it was in .... but I want it to return ... Can I do this with the PLC ???

Yes.

[soapbox]
Of course, the simpler solution would to use the correct tool for the task. In this case, that might be a single-solenoid valve. All too often, the person responsible for the controls is asked to perform some "magic" in the PLC to compensate for poor choices made during the design process. Sometimes, when you are able to do the magic, you're a hero. More often, you become the enabler for the people who are too lazy to put in enough time to make an informed choice form among the options available.
[/soapbox]

Using a single-solenoid valve like Steve mentioned would be the easist. Logically you could simple put it the logic if you are not energizing output 1 then energize output 2.

when deactivated it stays at the position it was in .... but I want it to return ... Can I do this with the PLC ???

Click to expand...

besides asking "can it be done?" you should also consider the safety aspects of "should it be done?" ...



point: the system might be programmed to work perfectly during normal day-to-day operations - but what will happen if (actually WHEN) the power fails? ... in SOME (but not all) systems, this could have serious consequences since the PLC will lose control of the machinery ... what will the hydraulics or pneumatics do in your particular case if the valve isn’t “returned” as intended? ...



you need to think this through in terms of ideas like that ...

Why not just use a slave relay with changeover contacts on a single PLC output.
Andybr

In a way Steve is right but you have to ask more questions.

Is it a double solenoid valve in that the spool remains in place after it is shifted? Or is it a double solenoid valve that is spring centered? This means that the valve will return to neutral when the solenoid is deenergised.
In either case you should use interlocking logic like a reversing motor starter.
If you are starting from scratch go get the right valve...a single solenoid spring return.

I believe Gas is right. It is possible (but not common) to have 3 position spring centered air valves. Also to have two position (two coil) detented hydraulic valves.

Not enough detail from the original poster.

You can use a 2 position "maintained" solenoid(the last position energized is maintained), or you can use a 3 position solenoid valve that will default to a "center position" (via spring) upon removal of either signal. The default center position can be of various port configurations, depending opn the system requirements. Sound like you need to identify the system requirements before you make a selection. If you make the wrong choice now, you may have to try to overcome the result with programming, which is not preferable.