scot said:
I setup a lot of temperature control systems for various furnaces but I am getting into more complicated/custom installations that require more than what the manufacturer of my temp controllers can provide (i.e. Eurotherm). Is there any particular product that someone might recommend which has some of the features of a standard temp controller but provides the ability to develop some custom code and doesn't charge an arm and a leg for adding additional inputs? Are there any PLC's that allow you to write custom code?
Scot
All PLC's allow you to write custom code, that is the whole idea
behind it.
PLC's are expensive in nature but they offer lots of things you can
do.
You can use a cheap PLC or intelligent programmable rely module to
interact with the Heat controller or, you can go full out and use a
PLC to do it all.
Most venders of PLC's offer TC/RTD etc. modules to be added and a
variety of IO. Code is done in ladder format for most.. Some use
basic and others use a form of gate array logic.
Some of the low end PLC's do not have TC/RTD modules, but you can get
signal transmitters to convert a TC/RTD over to RS485/232 to send
data to these low end units.
What a lot of people do is use a heat control unit like you are now,
but they link to it via RS323/485 over to a PLC to control and monitor
set points.
For you, you maybe interested in things like this..
http://www.unitronics.com/Content.aspx?page=ProductOverview3
Also, look at
http://www.automationdirect.com
They have lots of signal conditioners and PLC's to work with at a low
price..
Jamie