Inheco Control 96 + CPAC Ultraflat Notes (TEC/Peltier)

I picked up this Peltier system on eBay a while back. I guess it’s for heating eppendorfs as part of some larger system.  The device is an example of the sub-contractors/assemblies all the way down mentality  you see in so much industrial equipment. The control unit uses a Watlow 96 PID controller, and a Watlow LSTW driver, which they’ve put in an INHECO branded chassis.

When I received it the controller seemed to be misconfigured. The TEC wouldn’t heat, and could not be set beyond 50C. Datasheets for the CPAC Ultraflat state that it should be able to go to 70C. So I needed to do some fiddling to figure out what exactly was going on.

The LSTW driver doesn’t seem to be documented anywhere on the web, I couldn’t find anything similar on the Watlow website either, so it’s possibly some kind of custom OEM module they have… However, as far as I can tell it’s just an H-bridge taking a 12v input.

It’s controlled by two pairs of inputs from the PID controller, one sets the output positive, the other negative. So from what I can tell it’s using purely digital control.

Looking at the PID controller itself, output 1 and 2 are wired up. As is the RTD temperature sensor:

The Watlow control interface is a bit of a pain, but it’s functional enough once you know what’s going on, and I configured inputs/outputs as follow:

Sensor: Wired for 2 wire RTD 100Ohm Platinium.

Outputs 1 and 2 on, switched DC open collector output.

Output 1 set to control heating.

Output 2 set to control cooling.

I also set the control limits to +/- 100C. I’ve pushed it to 90C and it seems to work, though it takes a while to get up to temperature. Not sure what effect running it out of spec will have. Quick thermal image with a FLIR one below. When I can find my temperature probes I’ll probably try and do some more tests… That’s it for the moment, more pics below.