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Same relay contact wiring to PLC in parallel to solenoid

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NoviceInstrum

Petroleum
Nov 28, 2010
3
Hi
I have a solenoid wired to a trip relay contact which is programmed to trip on high temperature. The trip relay is having only single contact. Now I would like to wire this trip relay contact to a Allen Bradley MicroLogix PLC so that I know when the solenoid is tripped via the relay contact. I am planning to connect the contact to PLC's digital input as per the attachement. I think it should work. Your comments please.
 
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No attachment..

Probably NOT a good idea because the solenoid will be generating occasional LARGE spikes when de-energized. The PLC will have built-in snubbers to accommodate that but they're typically not designed to handle solenoids only smaller relay coils. You should consider using a second relay or much much better a two pole relay and just use one set of contacts for the PLC.

Keith Cress
kcress -
 
switch_oja8ya.png


Hi Novice.

That will work just fine. For some reason I thought you where talking 120/240VAC not DC where a freewheeling diode directly across the coil does a great job of dumping off the spike.

Is that really -24V??? or 0V?

Keith Cress
kcress -
 
Was wondering the same. I bet a nickel on 0 V. Maybe even a grand.

Gunnar Englund
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
 
With a boring life like mine - I can't help seeking excitement whenever possible.

Gunnar Englund
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
 
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