STC1000 Temperature Controller (a beginner’s guide)

For value for money, you can’t beat an STC1000.

There might be better temperature controllers out there, but this is the one I’d recommend over all others.
You can buy them fairly cheap off ebay for about a tenner, but you need to wire them yourself (it’s easy).

Don’t worry about the manufacturer, an STC1000 is an STC1000, regardless of who made it.

Just be sure to check whether you got a 220v or a 12v unit. This guide will assume that you have a 220v unit.
If you get a 12v remember that you’ll also need a 12v power supply, 12v will die in a flash of blue light if you run 220v through the power.

I take no responsibility for anyone’s equipment. This is an informational guide and it’s up to you to make sure everything’s safe before plugging your STC in.

(Working with Electricity can be dangerous or fatal. Make sure you have a qualified, competent person to confirm all wiring is correct before use.)

What does it do?
It has a probe that sends temperature data back to the unit. The unit then powers either a heat source (eg brewbelt) or a cold source (eg fridge) based on what temperature you set it to maintain. The result is that you can keep your fermenting wort stable at the temperature that you want to ferment at.

How does it do that?
All the magic is hidden in the unit and you don’t really need to worry about it. But basically inside the box are two 10AMP 12Vdc SPST-NO sealed relays (spec sheet) that act like automatic light switches.
When the temperature probe says your wort is hotter than you set the unit it turns on the cooling switch, and when its too cold it turns on the heating switch.

For nerds: HERE are the internals (very simple stuff).
Some boards can be connected to an Arduino for programmable fermentation profiles etc, but getting one is random.
If want to see if yours is one of these versions, take it apart and check this thread.

Why would I bother?
If you don’t ferment at stable temperatures within the yeast’s range you will get off flavours, or maybe you won’t ferment at all!

Summer is warm – too warm for lager yeasts, and even too warm for most ale yeasts, so unless you want to brew crazy belgians and wheatbeer all summer you need to cool the wort.

Winter is cold – too cold for most yeasts, so unless you want to brew lagers all winter you’ll need to warm the wort.

Unstable temperatures are bad. You want to keep your wort fermenting at a stable temperature, without the warm/cold cycle of day/night.

Right, you’ve sold me. What comes in the box?

  • The unit – this has an LCD display to show the current temperature and help navigate the settings. It also has 8 wiring connectors on the back. Two orange clips are connected to the sides for securing the unit in your housing.
  • The temperature probe – Just a long wire (2 meters) with an electronic thermometer on the end.
  • Instructions – I’ll go into the usage later on. The instructions are pretty non-existent for the wiring and confusing for the menus.

What else do I need?
It really depends on how far you want to go. You can spend a lot of time getting parts to connect for different appearance and slight tweaks, but for this intro I’ll stick to the basics.

You’ll need a length of wire (1.5mm), 2 female sockets (power out), 1 male plug (power in), 1 connector strip (min 10amp), a box.

For this build I spent about a tenner (sockets €2.49 x 2, plug €2, wire €3, strip €1.79), project boxes vary from about €5-15 if you want to be fancy about it.

For tools, you’ll need a small flat-head screwdriver and a knife. (you can also use things like a hobby drill if you want)

Ok. I’m ready. Let’s do this! But how?
I’m not going to go into how to install the unit in to a fridge, bypass thermostats etc.
Instead I’m focusing on how to make a standalone unit.
The first thing you’ll need to do is decide on a case to house it. You can get project boxes in Maplin, use tupperware, a Chinese take-away container, whatever!
I chose this case that some hobby drill accessories came in, because I wanted to see inside.

Next make up a quick mock-up of how you want it.
This will ensure that you have all the bits you need, allow you to adjust distances, and give you a picture of what the end result will be.
Here’s a picture of my mock-up for this project. It helped me to see that such a short mains lead would be a problem and fix it early.
I also did the simple wiring of the plug/sockets at this point.

Once you have a layout and all the bits you need, make any alterations to the housing box to accommodate the unit and any wiring.
I put 1 hole for mains, 1 hole for probe, 2 holes for output.

Next is the bit that people back away from, the wiring. But don’t worry, if you managed to wire the plugs you’ve more than enough skill to wire the rest.
Here’s a wiring diagram to show what needs to be done. It can be done slightly differently if it suits you, like THIS way suggested by Tube.
A word of warning though, the connectors on the STC1000 are quite fragile, so treat them like a lady.
Be patient, hold them softly and screw them gently.

From this we can see that we need 3 short lengths of red/brown wire, and 1 short length of blue.
Here’s how they look in real life.
Live wires will go to 1, 5 and 7.
The neutral wire goes to 2.
Again this quick mock-up helps to get the wire lengths correct.

Now that we have the odd bits of wire sorted out, lets look at it together with the output wiring
You’ll see that both green (earth) outputs go to one block, both blue (neutral) go to another block and both brown(live) go to the outputs on the STC unit.

This final bit can be a bit fiddly if you chose a tight housing, but take our time and it’s easy.
You just need to get all of the wiring into the little connectors on the back of the unit.
Next attach the incoming power connectors to match, and attach the temperature probe (connectors 2&3)
Finally, secure the wires from pulling with a few tight zip-ties.

After a bit of tidying, you should now have a working STC1000. Get it all closed up and plug her in to see the temperature.
You’ll notice in this final picture that I marked the hot and cold sockets. This will save you grief later on, trust me…

What else do I need?
You’ll also need a heat source and a cold source.
For most people, the cold source is an old fridge.
I use a brew belt as a heat source, but other people also use tube heaters, or simply an old style 100W light bulb under a terracotta plant pot, etc
It’s best to strap the probe to your FV and cover it with insulation. Packing foam works great. The reason for this is so that you get the temperature of the fermenting wort instead of the ambient temperature of the air. This will keep the reading stable when for example you open the door and let all the cold air out.
When possible, have the wires exit your fridge through the top of the door near on the hinge side. This keeps the best seal.

What does all the stuff on the screen mean?
When you plug it in, it will come to life and show the temperature.

If the heating socket is live, you’ll see a little light on the bottom left.
if the cooling socket is live, you’ll see a little light on the top left.
If the cooling light is flashing, this means that the temperature has recently got too high and cooling will start after ‘compressor delay’
If neither are on, then you’re at the set temperature.
If the ‘set’ light is on (to the right of the cold light), you’re in the settings functions.
Some models have a °C symbol on the top right, others don’t.

It only has ‘ERR’ printed on the screen and it’s giving a high pitched tone! What’s going on?
This just means that the temperature probe it now connected properly.
Unplug the probe and plug it back in again.
If it continues, borrow someone else’s probe to see if that works.

What do the buttons do?
There are 4 buttons to the right of the screen:

  • On/Off – hold for 3 seconds to turn the unit on or off. It also acts as a ‘finalize’ button to confirm settings.
  • S – The ‘settings’ button. Hold for 3 seconds to get into the Functions menu.
  • up/ down – used for changing settings.

What are the functions?
The STC1000 has 4 functions.

How do I set them?
Hold down the ‘S‘ button for 3 seconds to get to the functions, once you see ‘F1‘ on the screen, release the button and use the up/down keys to scroll through F1/F2/F3/F4
Once you are on the function you want, press and hold the ‘S’ button and use up/down to change the value.
When the value is set, release the ‘S’ button and hit the on/off button to finalize it.

I lost my instruction leaflet :(
Never fear, I found you a new one :

I want something important added to this guide, or something incorrect changed.
Reply and let me know what it is.

I’m proud of my STC1000 and want to show it off!
I’ve shown you mine, now you show me yours.


Follow the thread on the forum

Author: LordEoin

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