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Dear /diy/nosaurs,
I am planning to convert an old fridge into a fermentation chamber so that I can brew beer at home. Most people in the homebrewing community seem to use something called STC-1000, an inexpensive temperature control unit, which is basically just a temperature sensor hooked up with an MCU and two relays, that switch the fridge and an (optional) heat source
I have some experience with low-voltage circuits, but I have never really built anything that runs on the mains and I am not sure how reliable these cheap Chinese electronics are. Most people seem to do fine with just wiring up the control unit with the fridge, but they are mostly homebrewers with little to no knowledge of electronics. So I was thinking about some extra precautionary measures:
1. install a simple fuse so a current surge does not destroy the thermo control unit
2. use extra, higher-rated relays to switch the fridge on/off so that the relays in the STC-1000 only have to switch a few milliamps.
The built-in relays are rated for 10A, so I think they should be enough to switch a smallish refrigerator, even after accounting for the current surge upon powering up the compressor, but I really want to be on the safe side here.
What would you say, /diy?
tl;dr: I want to use an inexpensive temperature control unit to control a fridge and I don't want to burn my house down.
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>>1009570
Those controllers are designed to handle compressors and heaters. There is even a "compressor delay" on them so you dont burn out your compressor.
The built in relays are beefy enough for fridges dont replace or supplement them. You can add fuses if you want, but I never saw a need.
I used mine to make a sous vide setup with a crock pot. It handled the load of the crockpot on "high" just fine.
For your heat source, a ceramic lamp base mounted inside a quart sized paint can will work. Put 60W incandescent in there and plug it into into your "HEAT" side of the PIC.
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> OP wears a belt and suspenders...
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>>1009570
There may be a better way of doing this. Depending on how household refrigerators work, cutting power to them may be noisy and hard on the system. I suspect that there is a fairly simple method of interfacing with the temperature controller inside the fridge to give it a false reading, enabling you to turn the compressor on and off.
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STC1000 will works well for many applications. Ive used them extensively for controlling steam valves for heating projects and other direct and indirect heating/cooling applications. The thing that sucks about them is the piece of shit NTC probe.
Get an SL9696 instead with a good RTD. Its got serious control functions. Plus, you can get a sweet RTD and control your shit to winthin like .1 degree F as well as 4-20ma output for temperature logging. You can hook it up easily to a computer as well and control your process like a boss.
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>>1009572
Get a cartridge heater. Dont be a fucking gypse and try to use a lightbulb. Shit will fail. Build it right the first time. Size the cartridge heater correctly.
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I used the STC1000 to buil a warm room for when I hand-feed new born parrots, worked fine so far.
It's cheap and does the job.
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