Slc Temperature Control

CHRISTIANTECH

Member
Join Date
Aug 2004
Posts
3
I have been asked to upgrade a packaging machine using a SLC 5/04 and was wondering which is easiest to use, 1746-NT4 or 1746-BTM. The BTM is about double the cost but I need this to be tightly controlled and thought the autotune might be best. I will be using 2 ssr's to fire the heaters. I haven't designed a system like this from scratch before so any sample code would be most appreciated.
 
greetings, Christiantech,

I'd like to help but I'm sorry that I've never worked with the BTM module ... but since you seem very eager to get some type of response, I'll post this until someone more knowledgeable comes along ...

1746-BTM User Manual

this has some example program rungs near the back ... also just reading through the user manual should give you a pretty good idea of what you're getting into with this animal ...

and while you're reading, here's the:

1746-NT4 User Manual

for comparison ...

and have you already searched the forum for "BTM"? ... I got a couple of hits that you might find interesting ...

finally ... most of the "big dogs" seem to visit the forum at night ... maybe you'll get some better answers in the morning ... what's your deadline on this project? ...
 
Last edited:
The BTM (Barrel Temperature Module) is designed for a specific type of application - barrel temperature control on plastic extruders and injection moulding machines.
These have several heaters along the length of the barrel (zones) and in some cases the zones also have cooling provisions.
The module's algorithm takes account of heat transfer between zones that it determines during auto-tune. Each zone has its own setpoint and must be configured as either an internal or end zone. Outputs for each zone are percentage on-time bits for heating and cooling.

I've used the larger version (1771-TCM) on an injection moulder with excellent results. A colleague installed a BTM on an extruder, also with excellent results. The auto-tune works. The example code in the manual works. Just one recommendation - keep the cycle time for the percentage timers as low as practical. About 5 sec. for SSR's.
 
CHRISTIANTECH,

I did a project last year with a SLC-5/04 and the 1746-NT4. The NT4 works well to input temperatures from thermocouples. You tell the module which types of thermocouples that you are using by writing a word to the "output" address of the slot where you install the NT4 Input Module! It sounds crazy, but this is now common for many of the Allen-Bradley modules, and it works great. I had no problems with reading about 20 type J & K thermocouples, and the temperatures were very accurate.
 
I've been able to replace my BTMs with NT8s (the NT4's bigger brother) with good results. When you say tightly controlled, how tight are you talking? The NT4 should do you within a couple of degrees with not much effort.
 
The BTM module will be the easiest to set up and tune. To acheive tight control would require the use of the plc's PID function which isn't rocket science but the BTM module does all the controlling on board with the minimum of programming. For example using a standard t/couple card the output of the pid function would have to be converted to a time proportioned output in the ladder program, this needs to be done for every loop.The BTM also isn't just designed for extruder barrel temp. control, the controller can be used in barrel or non barrel mode.
Pauly
 
Thanks all for the feedback. I will be under a very tight startup schedule so for ease of setup and tuning I think I'll use the BTM.
Again, thanks.
 

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