plc wiring basics


Thread Starter

Mike Piotrowski

for example, I am going to use a PLC to monitor a convection oven. I will use an output from the oven (wired in sink, not N-Synq) with a 12 V power supply from the oven as an input to the PLC. Other inputs will be proximity sensors and fault signals, the outputs will be buzzers, pneumatic valves, led's etc. Is there a website that can show me some of the fundamentals such as sink vs. source wiring etc??

Rajesh Kenge

Try, I think this website will be useful to you. Also you check the catalogues of PLC manufacturers where wiring of the i/p and o/p
channels is clearing given.

Regards rajesh. 12/6
Hi Mike,

I don't know a website which could help you.
I'm ready to send you some of our documentations as an example (just one way among 100,000 others) if you drop me an e-mail.
[email protected]

Guy H. Looney

All you really need to remember is that you're completing a circuit. The terms sinking and sourcing are seldom reliable because manufacturers, vendors, distributors, etc. aren't consistent with how they use the term. I seldom rely on what people tell me a device is. I ALWAYS qualify what they mean. If they tell me it's sourcing, my response is " you're providing a voltage/current when it's turned on, right?" If they tell me it's sinking, my response is, " you're providing a ground when it's turned on, right?". I think it's imperative that you do that. Once you know for
sure what the device is, the only thing you have to do is complete the circuit. If an input device is sinking (providing a ground when it's on), the input module needs to be "pulled up" to the appropriate voltage (5VDC, 24VDC, 110VAC, etc.) to complete the circuit. The opposite is true if the device is sourcing (providing voltage); the module needs to be "pulled down"
to 0VDC or neutral if it's AC voltage. Outputs are normally just two pole devices. They're really easy to work with. If you have a buzzer that requires 110VAC across it's coil connect one side to the output module and the other side to the appropriate voltage level. If you have a sourcing (providing voltage/current) output module, the other side of the coil should
be tied to 0VDC or neutral if it's AC. The opposite is true if you have a sinking output module.

Remember, keep it simple. All you're doing is completing a circuit. The most important thing to remember is that you want to verify what somebody means by sourcing or sinking.

Let me know if I can help any other way.


Guy H. Looney
Motion Control Engineer

A.C.E. Systems, LLC
work: (615) 754-2378
fax: (615) 754-0098
cell: (615) 330-0044
[email protected] <mailto:[email protected]> <>

Sam Robinson

One good source for info on how to hook up PLC I/O cards can be found in Automation Direct's catalog. They have examples of how to hook up each of their cards and show sinking/sourcing configurations. Go to and request a copy of their free catalog. It is loaded with a lot of good info.

Sam Robinson
[email protected]
Industry Products Co.
500 Statler Rd.
Piqua, Oh 45356

Darwin Frerking

Look in the PLC manual. Most manuals have examples on how to wire to the various I/O modules.