Cheap thermostats for fermentation chiller?

[BetterSense]

I made one fermentation cooler out of foam, using a house thermostat that I had lying around. I want to make another one but I don't want to spend $15-25 on another house thermostat. I have microcontroller hardware to implement a thermostat but that will add up to $15 or so too. Has anyone found an ultra-cheap ebay or dealextreme thermostat? It literally just needs to switch a switch. I have some of those snap-switches they use for thermoelectric coolers but you can't adjust them.

 

[ehedge20]

$15 for a thermostat is dirt cheap..... Maybe you could call MacGyver, get an egg timer, a paper clip, and a band-aid?

 

[camiller]

If you are really trying to get cheaper than that you might need to look to less conventional sources. You might try a habitat for humanity "Re-Store" that sells used construction materials for a used thermostat. Think outside the box(store).

 

[BetterSense]

I actually designed one with two thermistors in a wheatstone bridge, and an LM311 comparator and a small power transistor. Total cost: free cause I had the stuff.

 

[mredge73]

There is a thread on here somewhere (I cannot find it at the moment) that shows how to adjust the cold control thermostat built into a Fridge/Freezer with an adjustment screw. If you are using a fridge with an adjustable cold control then this is a $0 investment.

 

[camiller]

There is a thread on here somewhere (I cannot find it at the moment) that shows how to adjust the cold control thermostat built into a Fridge/Freezer with an adjustment screw. If you are using a fridge with an adjustable cold control then this is a $0 investment.

Sounds like he is building a styrofoam box not using a fridge.

 

[BetterSense]

Actually I ruined my mini-freezer by drilling into the freon tubes. I soldered the tubes, but it's probably not worth trying to get it re-charged, so I'll probably repurpose it as an icebox/fermentation chiller.

 

[jawe]

maybe this can help you.
Thermostat Controller with Relay using LM35 and TL431

it cost only $5 to build.

 

[mredge73]

Well, then you can remove the cold control from it. It is nothing more than a mechanical thermostat switch that can be adjusted with a set screw.

Found it:
https://www.homebrewtalk.com/f51/gu...mostat-32f-eliminate-external-control-249612/