SLC and temperature control

I am wanting to control some heaters with my SLC 5/03 but instead of using regular temperature controls I am going to use a 1746-NT8 (termocouple card) and a 1746-NI4 (analog out put card) I am also using Watlow SCR's with a 4-20ma input. the question is I want to be able to control these SCR's like you would in a standard temp control, but just using the SLC does any one have examples of the PID loop I would need to use and also does any one have any Idea on how to Auto tune?
Thanks
Shocker

shocker1898,

Do a search on the forum for smc or hot rod. You will get plenty of info.

Bob O.

You could take a look at the 1746-BTM card

see

http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1746-um010_-en-p.pdf

It has an autotune feature

Unregistered said:

You could take a look at the 1746-BTM card

see

http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1746-um010_-en-p.pdf

It has an autotune feature

Click to expand...

I remember using these when they first came out about 5-6 years ago in a blow mold (milk jugs) application and that they worked quite well. $.02

Temperature is typically a slow variable to control. IMO it would be simpler to use solid state switches and pulse width modulate them from the PLC. You can even get away with a simple band control (maybe 3-4 error ranges) that result in differenct duty cycles to the heaters. In other words, high duty cycle with large error and smaller, but adaquate duty cycle when close to setpoint.

Yes, but...

shocker1898 said:

but just using the SLC does any one have examples of the PID loop I would need to use and also does any one have any Idea on how to Auto tune?
Thanks
Shocker

Click to expand...

First checkout the hotrod.zip in the download area.
It took years for me to learn how to do an auto tune. Your question is like Grass Hopper asking master Po on Friday if he could learn kung fu in time for the Saturday night bar fights.
Unless you really want to know how to autotune something you should consider a heater controller with auto tuning built in.