Current Loop To AB PLC


Thread Starter


Currently send 20mA current loop to RS232 converter to serial ports on a PC which runs a C program and writes the data to the Allen Bradley PLC 5 using RsLinx SDK

Is there a way to send the 20mA current loop directly to the PLC. I.E.... An input cars or something
Im not sure whether your are talking about process signals or a CL comm link so I hope this helps.

Premise 1: You are talking about a communications link and NOT an analog process signal.
I installed a system about 15 years ago that used a RS232 current loop at 20mA connected to a PC and six controllers. Try "": . That is where I bought the RS-232 to CL converters. As far as a communication network goes, its a very troublesome and
crude method, there is no way to direct broadcasts to one machine. It was what the customer wanted, but I'll never do another again. Every device hears all communication and has to interrupt its tasks to determine independently with software whether its relevant or not. No tokens, hardware handshaking, collison detection, etc. You can use the PLC5 RS232 port but you'll have to modify your program to read/write from/to it yourself, it won't do it a transparently as RSLinx does. The PLC ASCII instructions are not as elegant as C for handling strings, but it can be done. If it is a communication system your talking about, why not just upgrade your PLC processor to say a 5/20E with ethernet and save the headaches.

Premise 2: You are actually talking about getting an analog process signal into the PLC so just install some analog input cards.