Automatic Direct

I had a problem with an Automation Direct input module…I’m not sure exactly what was happening. I have two proximity switches plug into two different junction box receptacles. When I would activate any of the two switches the other one would also go high. Each junction box receptacle terminated to different input modules, but they shared the same 24VDC supply. When I check input voltage on the switch that I would activate it showed 24VDC and on the other switch I measured approximately 10VDC at the input module. It did not matter which switch I would activate the results were the same just opposite of each other.

Accidentally, I bumped one of the input module and the switches started working normally. I notice a loose neutral wire that link the two module together. I tighten the loose wire and the system is working just fine now…exactly what was going on I’m not sure, can someone help me understand this phenomenon.

Thanks

rmonroe

rmonroe,

You said that you found a "loose neutral wire". Because you were talking about 24 vdc inputs, I ASSUME that you mean a loose 24 vdc Common wire. A loose common could cause the second prox switch to act as a "common" sink for the first switch. In other words, if you have a loose connection to your input module, all bets are off, and you can get some very strange effects.

The first thing I check are the LED indicators on the PLC modules. The second thing is to start grabbing and pulling on each wire to see if it is loose. It is amazing to the inexperienced how a wire that was tight at installation can become loose after a few weeks operation. This is known as "wire creep" and is the rule rather than the exception, so I am not surprised at all that you found a loose wire. I will not bore you with the reasons why this happens, but you should go back and check all the other wires also. You will probably find 2 or 3 more loose ones.

Lancie1,

You must be a patient person.

thanks for the infor.

Thanks for information and support...Your right It was a loose common.

rmonroe