DIY STC-1000 2-Stage Temperature Controller Wiring Diagram with Indicator Lights

Time to go autonomous.

Growing tired of swamp cooling for fermentation “temperature control” I’ve decided it’s time to invest in the widely popular 2-stage STC-1000 “ebay” temperature controller.   And with a spare mini-fridge from college simply sitting in the detached garage-  why not, right?   This project in it’s entirety was inspired by the HomeBrewTalk.com community and countless user write-ups with similar projects (hey- credit where credit is due).   So let’s build this damn thing!  Here’s what you’ll need:

Parts List:

• QTY 1 – STC-1000 Digital Temperature Controller ($19.99 Ebay)
• QTY 1 – 120V Alpinetech 22mm Blue LED Indicator Light ($4.95 Ebay)
• QTY 1 – 120V Alpinetech 22mm Red LED Indicator Light ($4.95 Ebay)
• QTY 1 – 7″ x 5″ x 3″ Project Box ($7.49 RadioShack)
• QTY 1 – 10′-0″ 14 gauge replacement power cord ($13.97 Lowe’s)
• QTY 1 – 115V-1Phase-15A Black Receptacle ($1.99 Lowe’s)
• QTY 1 – Bag of 6/32 Nuts ($1.18 Lowe’s)
• QTY 1 – Bag of SAE No. 6 flat washers ($1.18 Lowe’s)
• QTY 1 – Black Outlet cover ($0.39 Lowe’s)

Tools List:

• Wire strippers/cutters
• Screw driver
• Dremel (or other cutting tool)
• Power Drill
• Step Bit
• Needle nose pliers
• Voltmeter

Total Cost $56.09

Depending what you have in your garage-  you may need to purchase additional incidentals such as wire-nuts ($2.58/bag), Dremel cutting tools ($6.18/cylinder), etc., etc.  however I’ve excluded these items from the above parts list as most DIY-ers will already have these items on hand. 

The LED indicator lights are completely optional.  The reason I (and many others) choose to include indicator lights is to have a clear visual display communicating whether the controller is calling for either cooling (blue) or heating (red).  These 120V LED lights from Alpinetech are truly a perfect fit-  small enough to fit into a project box yet big/bright enough to see from across the room, affordable (at $4.95/each), and most importantly.. the correct voltage (120V/1Phase) for this application. But it is a place to shave off $9.90 +S/H from your bottom line-  just sayin’.

Step #1  Time to get into the weeds;  the wiring diagram.

So… If you are now lost…  STOP! And- to be fair… I’m also not an electrician and electricity is extremely dangerous. Consult a certified and-or licensed electrician to check your work if in doubt.   This write up is a guide (and not the gospel). Do not risk your life to save money as there are several commercially available pre-assembled  temperature controllers in today’s marketplace.

Step #2  Break the bridge.

A very important step in the above wiring diagram is to break the bridge (-or tab) connecting the two hot terminals on the receptacle.  By doing so- it allows each outlet to be positively charged independently from one another.  -Or for this project-  it allows you to have one outlet for cooling and one outlet for heating.  I was able to remove the bridge with neelde nose plyers and a little “persuasion” as shown in the above images.  No need to remove the bridge on the neutral side as the receptacles can still share a common neutral connection thus reducing the number of wires needed.  (See- saving both time & money already!)

Step #3 Templates are amazing. 

Once you’ve figured out how you want the finished controller assembly to look create a template(s) (and make copies).  A simple template will save time and limit ones frustration while cutting out the openings in the project box.  Hey -it’s not brain surgery-  but a little precision never hurt anybody.

Step #5 Let er’ rip!

Begin cutting out the required openings.  Remember- a hole can always get larger… however making a hole smaller requires a magician.  Cut conservatively.

Use Step Bit for indicator lights.

The receptacle openings aren’t “totally” round. Use Dremel for receptacle openings.

Step #6 Confirm opening sizes.  Repeat Step #5 as necessary.

Step #7  Drill a hole for the power cable & temperature probe.  Time to begin the wiring process.

Now that you’re an expert cutting openings in the project box using either a large drill bit or a step-bit cut a hole(s) for both the power cable & temperature probe.  No need for a template here as you are now an expert project box surgeon- remember?

Step #8 Moment of truth…

Well it looks the part… now it’s time to test out your wiring skills…  This is also a great time to confirm both outlets are truly operating independently.  When “cooling” is activated-  the receptacle wired for “cooling” should read ~120V and the “heating” receptacle should read 0V.  The reverse is true while in heating.  The below screenshots should help illustrate this test.

In “Cooling” Mode.

In “Heating” Mode.

~120V for active charged receptacle.

0V for inactive receptacle. Success!

Step #9 Close the project box and have a victory brew.

It also helps to have a Celsius to Fahrenheit conversion table.  I found mine via our friends at homebrewtalk.com:

http://www.homebrewtalk.com/f51/fully-temperature-controlled-fermentation-chamber-about-200-a-175456/index2.html

Lessons learned?   -Of course.

1)  The screws to secure the receptacle to the exterior wall of the project box simply weren’t holding under the pressure of plugging/unplugging power cords.  A quick fix was to use #6 flat washers & #6-32 hex nuts to keep the receptacle mounted in it’s proper place.

2)  Was cooling the left -or the right receptacle?  Label them to save yourself the headache of tracing your bird nest of wires.

Now time to build the fermentation chamber 🙂

-Cheers