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Project: YATC 2 - General Applaince Temperature Controller
Date:January 2011


This temperature controller is available fully assembled with all accessories or as a complete kit that requires soldering. It is ideal for the following:

  • converting a chest freezer into a refrigerator
  • converting a dorm fridge into a cheese and wine refrigerator
  • converting a hot plate into a temperature controlled cooker
  • converting a camping cooler into fermenter
  • converting a crock pot into a sous vide

On our homestead we use multiple temperature controllers each day which saves us hundreds of dollars a year in time, food and electricity.

  • sous vide ( 132F - 185F )
  • chest freezer to refrigerator ( 35F )
  • bread rising ( 78F )
  • cheese making ( 72F - 108F )
  • wine making ( 75F )
  • yogurt fermentation ( 110F )
  • kimchi fermentation ( 72F )
  • kombucha fermentation ( 74F - 84F )
  • tempeh fermentation ( 85F )
  • cheese fridge ( 50F - 54F )
  • wine fridge ( 50F - 57F )
  • waste vegetable oil ( 90F - 120F )
  • soup stock ( 180F )



Choose Kit or Assembled unit from drop down menu below.

All shipping is Priority Mail based on the country you are located in, as follows:

Please choose the correct item and country to avoid additional fees and delays.


The design is completely open with source code, schematics, circuit layout and bill of materials all made available.




  • 3-digit 7 segment LED digital display
  • Heating versus cooling is set to 65F (over 65 is heating under 65 is cooling)
  • Tolerance: +/- 1 degrees (when temperature is set over 65F)
  • Tolerance: +/- 3 degrees (when temperature is set below 65F)
  • Temp Range: 0F - 255F
  • Temperature output fahrenheit
  • Max Swiching Amps: 15A @ 120VAC
  • Circuit Power Supply (included): 5V / 1A
  • IEC 120VAC Wall plug (included)
  • Water Proof food grade temperature probe

Question:When I go to connect the power harness to the YATC does it matter which pink spade connector connects to the different metal spade connectors on the circuit board?
Answer:No, it does not matter which pink spade connector connects to the metal circuit board connectors. Either way will work.

Question:Is the food grade temperature probe water proof?
Answer:The metal portion of the probe is water proof. Do not completely submerge the probe in liquid past the metal to where the silicon begins or it will no longer be functional.

Question:How does YATC know hot or cold?
Answer:When the temperature is set to 65F or higher the controller assumes a heating device is plugged in. When the temperature is set below 65F it assumes a cooling application.

Question:What kind of power does this work with?
Answer:This temperature controller supports the following power configurations:

  • 120VAC, 50-60Hz, 15A
  • 220VAC, 50-60Hz, 10A
  • 12VDC, 10A

Question:How does this temperature controller connect to a chest freezer?
Answer:The controller connects to the freezers power cord using a plug-in outlet. No soldering or crimping required. There is a additional cable included with the device that plugs into the wall and a temperature sensor which is placed in the freezer. The temperature controller acts much as a thermostat and makes no connection to the chest freezers internal controls. This means that YATC can be used in combination with any existing refrigerator or chest freezers.

Question:Does this device use a PID algorithm?
Answer:No. The firmware gathers 64 samples and checks the temperature set point and enables a relay (turning on the heating or cooling device) when necessary. There is limited space on the microcontroller being used preventing the use of fancy math libraries and floating point operations.

Question:Do you ship outside of the US?
Answer:Yes! I use USPS first class for all international shipping. International shipping ranges in price. Generally $6 for Canada and up to $13 for Europe. Please e-mail with any international shipping questions.


  • plug pink spade connectors into circuit boards metal spade connectors (either one to either one, no orientation)
  • plug black DC adapter plug into wall and controller
  • use up/down buttons to set the desired temperature on the controller (35F is default)
  • press both buttons simultaniously to save temperature, hold for three seconds, (creating a new default)
  • unplug then replug black DC adapter and confirm that your temperature setting has been saved
  • place temperature sensor into chest freezer, camping cooler or liquid (do not submerge probe past the metal to where the silicon begins)
  • plug freezer or heating device into controller
  • plug black AC cable into wall outlet

Step by Step Kit Assembly:
These instructions are for the 2nd generation yatc controller which features a green circuit board and was starting in 2011. If you have a kit puchased in 2010 with a yellow circuit board see these instructions

Note: This kit makes use of mains power - 120VAC. Do not plug 3 prong IEC cable into wall socket until assembly is complete and circuit is verified to work.

Step 1: Blank PCB
Step 2: Place and solder 7-segement Display (D1)
Step 3: Place and solder Capacitors (C1) and (C2)

Note: These capacitors are polarized. The negative stripe must be over the round circuit board pad. The positive side goes over the square pad.

Step 4: Place and solder IC Socket (U1) with Processor (28 pin) (U2)

Note: There is a dimple on both devices that needs to be oriented on the right side of the circuit board.

Step 5: Place and solder 10 pin ISP header (J1)
Step 6: Place and solder a 470 ohm resistor (yellow/purple/brown/gold) (R1)

Note:On YATC2 and earlier boards a 1k ohm resistor was being used (brown/black/red/gold) (R1)

Step 7: Place and solder Diode (D2)

Note: The black line must be on towards right side of the circuit board.

Step 8: Place and solder transistor 2N3904 (Q1)

Note:The transistors flat side is facing the IC socket.

Step 9: Place and solder both tall push buttons (S1,S2)
Step 10: Place and solder sensor connector - 2.5mm jack (J2)
Step 11: Place and solder 100k resistor brown/black/yellow/gold (R2)
Step 12: Place and solder spade connectors (CONN2, CONN3)

Note1:The spade connectors are to be soldered on the top side.

Note2:On the YATC2 and ealier the silkscreen is printed on the bottom, but the component soldered on the top.

Note3:YATC3 has the silkscreen on the correct side (top).

Step 13: Flip circuit board, place and solder 5V regulator (U1)
Step 14: Place and Solder barrel jack (CONN1)
Step 15: Place and solder relay (U3)
Step 16: Peel off blue cover sheet on plexiglass case
Step 17: clear acrylic case
Step 18: Place 4 screws through longer acrylic sheet leaving two upper most holes empty
Step 19: Place long .8" standoffs over screws
Step 20: Place circuit board and short .4" standoffs over screws
Step 21: Place cover acrylic cover and nuts over screws. Leave finger tight.

Bill of Materials:



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