Hello all. I've had a bit of a weird one today and would like opinions.

We have a 110v ac solenoid. It's on a packing machine. It's happy to.sit at 110v waiting for a bag to.hit the switch to trim a thread that's being used to stich a bag or product up. Once the switch is hot the 110 drops and cylinder activated to cut. After about 1 second the 110 is reapplied. However when reapplied it's only 30v so the cylinder does not return. I have to physically remove the solenoid from the valve for the 110 to return. If I take.the coil on and off the valve stem it works.just fine. I don't get it. I'm.thinking of adding a 110 realy to open and close the signal.

Many thanks

 

must be a bad connection somewhere causing volt drop

 

So you have described a coil circuit with the contact on the common wire. Sketch your circuit.

 

@yankeedave,

In addition to looking at the wiring to the solenoid for loose connections and/or crimp connectors, have you investigated the "source" of the 110 VAC for issues?

You didn't say it but it appears this problem has just recently started? Or is this a new piece of equipment that has had this problem since installation/commissioning? Has this piece of equipment been in service for a long time?

You mention there is a cylinder involved. I have seen when solenoid-operated devices are mechanically binding or sticking the voltage measured at the solenoid coil can appear to be very low at one end of travel because whatever is being "operated" hasn't fully moved back to it's original position. Is this a pneumatic cylinder? Does it have some kind of spring return to the ready-to-operate position? If it's pneumatic are you sure the air source is clean, dry instrument air?

By the way, usually when the scenario I mentioned happens the coil draws excess current and eventually fails--or the excess current exceeds the contact rating of the switch and the switch/relay fails.

A photo--as well as a sketch of the circuit--would be very helpful (both can be attached to posts and responses on Control.com).