ON/OFF temperature control

markg

Member
Join Date
Dec 2005
Location
Long Beach
Posts
3
I want to replace our current, old temperature controllers with something new. These controllers are ON/OFF, have fixed hysteresis, and drive SSRs. I thought of trying a PLC. I need some info before I buy.

I have experience driving SSRs using transistor outputs, so that part is fine.

Can a basic 8-input/8-sinking output PLC with an analog input module (thermocouple) be configured to do ON/OFF control with hysteresis? Would I have to devise ladder logic to do hysteresis, or is there often a hysteresis function?

The PLC I am looking at is low cost and does not have PID loop functionality, so that is out.
 
Do you need to control anything else?

If not, then a PLC is a bit of overkill. A loop controller will do a very fine job with PID - and without any programming or need to purchase programming software for a PLC.

I personally prefer Yokogawa loop controllers:

http://www.yokogawa.com/ns/cis/utup/ut100/ns-index_ut100.htm

But there are many companies that make these with PID control and they are very inexpensive.

http://www.omega.com/ppt/pptsc.asp?ref=CN9000A&Nav=temp03
http://www.omega.com/ppt/pptsc.asp?ref=CN132&Nav=temp03


http://www.eurotherm.com/products/controllers/lde-lme.htm
http://www.eurotherm.com/products/controllers/series_3000/3216.htm

http://www.ab.com/industrialcontrols/products/relays_timers_and_temp_controllers/single_loop_temp-heater_controllers/900tc.html
 
Last edited:
Nice links. This will help alot.
4 controllers x $250 ea = $1000
I figured I could try a PLC for this much. But I realize now that I won't get the displays with the PLC, among other things.

Thanks for setting me straight.
 
Last edited:
Mark,

You can get a controller with thermocouple inputs and a display for under $1000.

We are currently working on an application with our vendor (who will also be our customer) whereby the solder machine we use in our manufacturing process, currently uses temperature controllers for preheat and solder pot tempterature. The new design will use one of our PLCs and a color touch screen. The cost for this configuration is over $1000 (PLC + touchscreen), however, if you don't require a touch screen, there are inexpensive text displays available. In addition to the temperature control, an analog output is being used to interface to an AC drive for conveyor speed control. So it isn't just temperature control.

The point that I am trying to make is that you will obtain far more capabilities with a PLC/operator interface combination than you will with just temperaturer controllers.

This application I mentioned above, will allow the operator to now store specific board profiles. The advantage to the manufacturer of the machine is far less wiring and many more features and capabilities.

So, don't abandon your original thought of using a PLC...because they are out there...and in the price range you are looking for.

Please note that I work for Entertron...an embedded PLC manufacturer. I don't know if this will assist, but we recently did a comparison of various micro plcs and their analog capabilities.

Hope this helps.

God Bless,
 
Last edited:
Thanks Stephen

I appreciate your feedback and the info.

One of the reasons I was interested in the PLC direction was the possibility of using PLCs to replace/enhance other control mechanisms in the lab (mostly logic circuits with relay outputs designed by yours truly years ago.) I entertained the idea that I might as well jump into it now even though mfgrs make temp controllers that do everything I could want for the immediate application. I'll look at your PLC solutions first.
 
If you are wanting to integrate other controls and/or tackle the learning curve, then the PLC is the way to go. If you go this route, by all means, bookmark this site and lurk around here. We'll be happy to help and would be interested in hearing of your progress.

If you had been looking for a quick and easy way to solve a temperature control problem then the loop controller is the fastest, easiest, and (usually) the cheapest.
 

Similar Topics

I have PID temperature control which will connect to Beckhoff EL4004(0v-10v). How I can program it to let EL4004 to control the temperature?
Replies
7
Views
2,607
Hi, Anyone have experience with Beckhoff temperaturer PID controller software library? BR Hans Pettersson
Replies
0
Views
2,143
Hi, Anyone have experience programming the beckhoff temperature PID controller block? BR Hans
Replies
0
Views
1,903
Hi, I have a 1500 that controls a station with diferents warehouses, but i also have a 1200 that controls one of those warehouses, i have been...
Replies
9
Views
226
A couple days ago I accidentally toggled an alwasyoff bit. The issue is it was set up as a single OTU on a rung, nothing else, and used as XICs...
Replies
3
Views
194
Back
Top Bottom