Output to solenoid

I have an output that goes to an air solenoid and when the output fires... it fires twice in rapid succession. Not sure what would cause it to happen... any ideas?

Can you be sure that the PLC code isn't doing the double firing? Maybe throw a quick diagnostic rung in there with a counter on the output, see if it counts up in ones or twos.

If you can eliminate that, I would be checking on the rating of the solenoid and the rating of the output. The solenoid will have a large inrush current, and your PLC output may be current limited - perhaps the output is throwing everything it has at the solenoid to try and bring it in, then limiting and turning off for a split second, then coming back on and this time making it the rest of the way to saturating the coil so that the current drops back to a manageable level. I never ever drive a solenoid directly from an output, I always use an interface relay for this reason...

What PLC and output card are you using?

I have seen this with contact bounce if you are using a PLC with a Relay Output.

We are using Flex IO with an 8 bit Relay output card....

1794-OW8 series A Output relay module.

+1 For a quick troubleshooting rung, as well as adding a relay between the output and the solenoid. We have burnt up quite a few output cards wired directly to solenoids.

So could we use something as simple as like an Icecube relay?

Ice cube relays, or solenoid driver relays would work.
I use these here almost exclusively now, high density, low cost, and easy to replace the individual relays if they ever fail. Haven't had any fail though in several years.

http://accautomation.ca/get-rid-of-surges-that-are-destroying-your-plc-outputs/

The above post explains the danger of DC Solenoids on PLC outputs. I always use an interposing relay.

Regards,
Garry
http://www.accautomation.ca

These are another option.

http://www.mcmaster.com/#7356k22/=y93wnq

They also have one for switching AC with DC control

not enough power in supply.

Make sure that the coil is not double addressed. Ive seen this happen before when there were two coils on the same address. One was off the same time the other was on. On the program it was constantly flipping because of the scan cycles changing it over and over. But it was on a DC light. I'm thinking the inductance is keeping that coil on after the second fire. Just a thought.