How to use the energy stored in a solenoid to trigger a 2nd action at de-enegize.

Here's my problem. In my system I have a 2 wire slip ring, which feeds power to a solenoid that when activated produces movement to grab an object. This is controlled by 24 VDC and fed from a relay, controlled by Yaskawa MP2300 motion controller. This object gripped is now occasionally sticking to the grip surface, I was asked to integrate a small ejector, without adding additional control wires to the slip ring. A small push tubular Ledex solenoid has been selected.

My analog circuit design are not good. Can anyone explain to me a circuit that will detect the solenoid discharge of energy and then direct that towards the 2nd small "pusher" solenoid? A mechanical engineer threw around some terms like clamping and/or zener diodes, but I'm not sure where to start. Lets assume there is enough power/current remaining to activate solenoid #2.

I would much rather implement this in ladder logic and add a 3rd conductor to the slip ring, but that is not an option right now.

// Mike

I doubt there is enough energy left! the only way I can think of is to have the solenoids work opposite each other from a common supply, so that when the grabber is "On" the ejector is "Off".

Maybe use polarity and diode isolation to control the two solenoids?

No Action:
SR-A = 0V
SR-B = 0V

Action 1:
SR-A = +24V
SR-B = 0V

Action 2:
SR-A = 0V
SR=B = 24V

Then use diodes to the solenoids on the moving side of the slip rings.

Can you use an alternating relay? You would have to change the logic that controls the existing solenoid. Presumably it is currently true when you want to grip and false when you want to release. You would have to change so that it is true all the time except that it briefly turns off and back on when you want to go from one state to the other.

I like rdrast's suggestion. That provides good, solid control very simply and fits in two wires.

Keith

I will give rdrast's solution a try and see how it works out. Thanks again!

// Mike

I've put rdrast's solution into work using diodes on the cable assembly found on the slip ring-side. This has been running in house for a bit and recently retrofited on a few machines in the field.

Thanks for the help. Sorry for the delay in replying.

// Mike