Jacob 02 (Customer) asked a question.
Will A 24 VDC Air Solenoid Coil blow up a PLC Card?
Hello,
I am having trouble with a PLC card point blowing up. Certains discrete output points on my output card will stop working after a couple days of use. The points that are blowing up are all turning on air solenoid coils. The solenoid coils do not have a diode to prevent voltage spikes. I'm thinking this could be the issue. The PLC car does look like it has an internal diode in it, but it's a Zenor diode. The PLC card is P3-32TD2 and the air solenoid coil is AVS-523C2-24D.
Does anybody have any ideas?
Thanks
my advice is to use the plc output to drive a external mechanical relay that will then drive the solenoid to prevent shorts and volt spikes that may ruin your plc, relays are much cheaper than plcs as well if one goes out, they are not as susceptible to voltage spikes and over current as the triacs they use internally on plc
Put a good meter in Max (Peak) record mode and cycle the coil voltage. What do you get?
Surge protection at the coil and interposing relays are the solution.
Yes, I'm going to put surge protection at the coil. Thanks
Or switch to the P3-16TR if you have room to place another card. Put 2 of these in the rack as these are relay outputs capable of 1.25 A per point (verses 0.2 A per point current card). Put diodes on the solenoids to protect the relay contacts from arcing and issue resolved. You could fuse each point, or fuse the common to protect from shorts.
The cost of two cards verses a single 32 point card is about $90 more.
I personally never use a relay card in a PLC anymore. An external relay is far easier to replace than one internal on the PLC card.