Peltier devices set up with STC-1000 controller for both heating and cooling to achieve constant temperature +_0.5

Thread Starter

Steveshep

Joined Feb 6, 2017
4
I’m trying to set up a water heating and cooling system using 3 Peltier devices connected to a digital controller STC-1000 (heating and cooling). To keep water at a content temperature 18C +-0.5 so heating below 17.5C and cooling above18.5C

The point is to heat and cool using the same Peltier devices by reversing the polarity, the problem I have got is the controller switches the Pos only (the Neg is constant). So how can I make it reverse the polarity on the Peltier to change from heating to cooling.

I have the device working well manually using a 6 pole DPDT Toggle switch (on-off-on reverse polarity). My problem is I can’t get it to work of the timer because it uses the common neg. these controllers are designed to use different devices for heating an cooling switching them ion and off ndividually .. I want to reverse polarity of the same device to do the same job .. but its got me stumped.
 

Thread Starter

Steveshep

Joined Feb 6, 2017
4
I guess I really need it to control (switch) both the neg and the pos in the same way as i can manually with the 6 pole switch, but how? if not possible with the STC-1000 does anyone know of a constant temperature controller that can achieve this function?
 

Analog Ground

Joined Apr 24, 2019
390
The STC-1000 controller I find has separate output contacts for heating and cooling. Is this your controller?

https://images-na.ssl-images-amazon.com/images/I/B1kOAUuVDWS.pdf

If so, a circuit with two SPDT relay functions would do the trick or a suitable DC motor controller. Something which gives an "H Bridge" configuration.

https://en.wikipedia.org/wiki/H_bridge

Here is the concept. It could go with mechanical or solid state relays or an H bridge DC motor controller. The key is using the heat and cool contacts on the temperature controller. Just replacing your hand and your switches.

PeltierHBridgeConcept.jpg
 
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Thread Starter

Steveshep

Joined Feb 6, 2017
4
Yes that is my controller (with the seperate output for heating and cooling).... Fantastic thank you for your recommendation & diagram ... I’m going to order the parts now.
 

Thread Starter

Steveshep

Joined Feb 6, 2017
4
Thanks Mate I used a couple of automotive 5 Pole relays it worked perfectly and has the advantage of reducing the load on the controller which was in danger of being overloaded going directly.automotive relays.jpgautomotive relays.jpg
 
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