Micrologics 1500 PID

Hi, I am new to the forum, but I am using the info constantly. I have a question that I hope some people can help me on. I am new to programing PLC PID loops, I just took a course in using the PID function for RSlogix 5 and I think the function is very close to the RSlogix 500. I am in the process of ordering a 1769-IT6 for the thermocouples. What output module for the Micrologix 1500 do you use to control SSR for heating? The SSR have 120V input, but I can change this if needed. Your input would be a great help.

Luke

Any solid state output will work.
You'll set up a timer that free runs & resets itself every second, then proportion your PID output to that 1 second, & turn on & off the output for the SSR. What outputs does the 1500 you have have onboard? If it's not relay, but solid state, you shouldn't need anything else.

Sorry I have relay outputs on the 1500, but I can purchase a solid sate output card, what do you recommend. I am still quite new to PID control, I don't understand the timer, do you have any ladder logix for this application, so I can see what you mean.Thank you.

If the process you are controlling is slow, for example, a heating application, you can still use the relay outputs but perform your time proportioning over a ten second period instead.

Well I hope I can explain this. Yes the application is slow, but the heating process is complicated I think. The heating elements heat up the metal to 900F but the element heat at 1500F when they turn on. The company recommends that the heating be done by PID that pulses the heater element so that the element never exceed 1100F, because then the metal in which the element is surounded in begins to aneal and shorten the life of the metal. I don't quite understand the this type of heating, but I hope it sheds some light on the application I am trying to use. Any sugestion and parts that I need would be a great help.

http://www.plcs.net/downloads/index.php?action=downloadfile&filename=MAIN_VAC V1-0-2.RSS&directory=Allen_Bradley&

This program has MLGX 1500 with PID loops controlling a valve by pulsing open/close and will work for a SSR too. A relay output will be fine for this.