Controlling 42VAC 250W heating resistance

[karkas44 0]

Hello everyone, I am dimensioning a project in which, among other things, I have to control a temperature through a 42VAC 250W resistance. The machine is already working but they want the control to be done again because it is currently working on a very old PC. Other machines have already been migrated to Allen Bradley 1756 controllers and they want a last machine to be migrated in the same way. Now, the other PLCs control these temperatures via Digital Outputs with a solid state relay, I assume they are implementing an ON-OFF control. I was considering using an analog output for this resistance but it would be necessary to amplify the voltage given that Allen Bradley analog modules offer only -10.5 ... 10.5 volts outputs. The Output Modules used are 1756-OB32 only, My question is, is it possible that there is another type of control used here? The use of the SSRs makes me think that there is the need to switch considerably fast, although these are not fast modules, so using PWM with them I think would be impossible, but I also think that a simple ON-OFF control for this temperature could be inefficient. Also, if I were to use an analog output, is there a pointing to an amplifier (Allen Bradley) that I could use for this application considering the heating element involved? Thanks in advance.

[chantecler 15]

Saludos paisano, Temperature regulation is usually a slow process. There is something called time-proportional control which is most probably what has been implemented on the other machines. RSLogix 5000 has an instruction you can utilize: SRPT The samples folder in your RSLogix installation contains a complete temperature control example. Take a look at it. Bye

[karkas44 0]

Saludos Chantecler, Thanks a lot for your reply.