How to build and wire an STC

I'm putting a full write up on my website later today but thought I'd post a short version here too.

The shopping list:
•220V STC-1000
•3 20mm IP68 Weatherproof Cable Gland
•Plastic Electronics Project Box (216 x 130 x 85mm)
•2 Trailing Mains Extension Sockets
•15 AMP Block Connector Strip
•13 AMP Fused 3 Pin Plug
•1.5mm 3core Flex Cable
•1ft Electric Tube (Greenhouse) Heater
•Under-counter fridge
Total cost c. £70 (including £20 fridge off ebay)
The bits!

Drill the holes. (Buy. A. Dremel.)

Wiring Diagram

My wiring!

All done! Simples!

Once the build is complete the probe itself needs to be calibrated against a known temperature such as boiling water or in my case I used a thermometer that I had already verified as accurate.
The STC has 4 settings:
•F1 – Temperature Setting
•F2 – Temperature Variance Setting
•F3 – Compressor Delay
•F4 – Probe Calibration Value
F1 is set to the temperature you require (19C in my case for fermenting an IPA).
F2 allows you to define how accurately you want the STC to get to that temperature. For example a setting here of 0.5 degrees will send power the cooler when the temperature reaches 19.6C, a setting of 0.2 will turn the cooler on at 19.2C.
F3 controls the delay in turning the fridge compressor on and off. Rapid switching the compressor on and off can reduce its working life, a setting of 3 minutes is pretty standard here it seems.
F4 allows you to calibrate the probe. I found that the default probe was reporting 3.5C lower than my trusty thermometer so if I set my STC to 19C with no corrections I was actually only holding a temperature of 15.5C inside the fridge! Not ideal for fermenting beer! This was corrected by setting F4 to -3.5 and now 19C is actually 19C!
And that’s all there is to it!
DA

Here you go.
http://demonvalleybrewing.co.uk/2015/08/31/diy-stc-fridge-controller/
It's supposed to be on my profile but that's not working as intended it seems! :P

Just copy that wiring diagram perfectly and it is easy enough. That's the bit I was most bothered by but it turned out a lot easier than I thought!

DA

I've wired a couple of stc's now, the first using the same diagram as the one you've posted. Second time, I used this one. No need for all those extra choc block connectors, and is easier to wire (I found, anyway). Diagram is a bit scrappy, but only two choc block connectors required - the other wires fit in fine, I just twisted them together. If I had a soldering iron I would have soldered them. The only change I made is the live wire to connector 5 (heater) comes from the top of the choc block, not the bottom, so there are 2 lives in each side.

Yep, that'll work too (and makes it marginally cheaper!) :P

DA

Made 1 yesterday using your guide and pictures.Turned out perfect,many thanks.
My missus came into the kitchen as I was sat at the table making it.She said I looked very suss,with the lunchbox and wires sticking out of it.

I made a temp controlller recently and is working perfectly- just trying to set it correctly as the freezer seems to be too good at cooling and even though turned off it cools a few degrees below target temp!

What temp do you guys set your keezer to?

AstroBrew said:

I made a temp controlller recently and is working perfectly- just trying to set it correctly as the freezer seems to be too good at cooling and even though turned off it cools a few degrees below target temp!

What temp do you guys set your keezer to?

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Depends really. What type of beer, using it to ferment, condition or serve......

ManseMasher said:

Depends really. What type of beer, using it to ferment, condition or serve......

Click to expand...

Serve and carbonate another keg (most the time)... so is there a middle ground?