$70 DIY Sous Vide Universal Controller

We love how our $50 dollar sous vide is precise and stable over a long period of time.

However, we thought it’d be awesome to create a brain that could control anything based on the thermocouple output. Something that would work with a rice cooker, bucket heater, or even a smoker.  We could’ve gone out and bought a $160 Sous Vide Magic, but we built our own controller for $70! And now we’ll show you how to DIY.

Warning: do not embark on this if you are not comfortable with electronics, including high voltages. AC power direct from the wall goes through some connections, which can lead to personal injury or death.

ALWAYS use this device with a GFCI outlet or adapter.

NB, we have both a MAKE guide and an Instructible!

UPDATE: We now have a kit to build your own sous vide controller for $80!  It requires soldering, but we think it produces an elegant and convenient result.


Hardware supply:

  • 2 foot air conditioner extension cord
  • 2 foot 12 gauge wire
  • 2 feet double stranded 18 gauge wire
  • Scissors
  • Electrical tape
  • Duct tape

Step 1: Power

Like the $50 DIY immersion heater, the most complicated step here will be providing power to the PID controller and output.  We will use both ends of the air conditioner extension cord separately: the male end will provide power to the PID and heater, and the female end will be our output socket.


Main power cord and output socket: Use scissors to cut six inches of extension cord from the female end (output socket). You should be left with 18 inches of wire on the male end (the main power cord).  For each end, carefully cut along the cord to separate the three wires: the two power lines and the ground (usually smaller, Fig 3). Now, strip the three wires on both ends by carefully squeezing the scissors at different angles on the cord until the insulator is detached (Fig 2), less than ½ inch should be bare (Fig 3).

PID Power cord



In order to pull out power for the PID controller we will cut our double-stranded wire in half ( the other half will be used for the relay control cord). Now split the wire in half (Fig 4) by a half inch. Strip the ends to expose the copper wire (Fig 4-5).  Choose ring terminals (Fig 6) that will fit on the screws on the back of the PID controller then use the crimper to attach the ring terminals to the ends of the wire. Separate and strip the wires on the other end of the cord just as in Fig 4 and 5— we later crimp this end and attach it to the main power cord.




Power relay wires: Cut the 12 gauge wire into three wires of equal length. Strip both ends of each wire so ½ inch of copper is exposed.

Splicing PID power cord and relay wires onto main power cord

Now we will attach two power relay wires and the PID power cord to the main power cord (the male end). Using the crimping tool, attach one end of a butt connector to a strand of the main power cord (not the ground; Fig 7).  Tug at the connector to make sure it will not come loose.  Combine one power relay wire and one strand of the PID power cord by flattening the copper fibers with your fingers and twisting them into each other (Fig 8-9).  Then put the combined bundle in the other end of the butt connector, and crimp tightly (Fig 10).




Again, make sure that the connection will not come loose by tugging on the wires. Then combine the other wire of the main power cord with the other strand of the PID power cord, and another power relay wire through the method used above.  If any wire comes loose, you may need to cut off the butt connector from the main power cord, strip the wire again and attach another connector.

Connecting output socket

Now connect the ground from the main power cord to the ground on the output socket using a butt connector.  Attach the third power relay wire to one of the two power wires of the output socket using a butt connector.  Then connect the remaining power wire of the output socket to the corresponding relay wire spliced off of the main power cord (to determine which is the corresponding wire, you can plug the main power cord into the output socket).


At this point, the only remaining free ends should be the two ring electrodes on the PID power cord and two power relay wires (one on the main power cord and one on the output socket; Fig 12).  Choose two ring terminals that will fit on the solid state relay contacts. Then connect those ring terminals to the free ends of the power relay wires. Be extra careful that these are crimped well.


Finally, pull on all your connections.  If anything comes free, reconnect with another terminal, and try to squeeze harder when crimping.  Safety is more important than saving time.

Step 2: Solid State Relay

Relay control cord: We are almost done stripping and crimping, but we first need to make a wire to allow the PID controller to activate the relay. Take the remaining length of double stranded cord, pull apart the wires at the ends, and strip them so that ¼ to ½ inch of copper is bare.  Choose spade electrodes that fit on the connectors at the back of the PID controller and attach four of those spade electrodes to the four wire ends (Fig 13).



From here on everything is easy peasy, screwdriver only work.  Connect one end of the relay control cord to the SSR terminals 3 and 4 by screwing down the spade connectors (Fig 14).  Connect the two ring terminals attached to power relay wires to SSR terminals 1 and 2 by removing the screws on the terminals, insert the ring terminals and tighten the screws firmly (Fig 14).



Finally, we must connect the SSR to the heat sink (Fig 15-16). The SSR is rated to 25A only if connected to a heatsink–otherwise the rating drops to around 7A, and decreases further at higher temperatures.

Step 3: PID controller

Now connect the two ring terminals on the PID power cord to PID controller connectors 1 and 2 (Fig 17).  Again, to do this: unscrew the connector, insert the ring terminal, and putthe screw back in.


Attach the free end of the SSR control cord to PID terminals 6 and 7, loosen the screws, insert the spade terminal, and tighten the screw again.  The wire from SSR terminal 3 should go to PID terminal 6, and the wire from SSR terminal 4 to PID terminal 7 (Fig 17-18).

Finally, attach the Pt100 wires to PID terminals 8, 9, and 10.  If the Pt-100 has three wires, connect the red, blue, and yellow to terminals 8, 9, and 10 respectively (Note Fig 17 is incorrect).  If your Pt100 has only two wires, connect the red and blue to 8 and 9, and then connect 9 and 10 together with a short wire.

One thing we noticed is that the Pt100 probe gives some wonky results if the back end gets even a little wet, we wrapped it up in duct tape and electrical tape to avert this.  Perhaps a better idea is to put the entire probe inside a finger of a latex glove, as we did in the DIY cheese vat.

You should also update your PID settings to save time heating up your water bath.

Step 4: Play!

The simple version setup can be seen in Fig 18. Plug in whatever heating element (immersion heater, crock pot, etc) to the output socket, and put the Pt100 probe in the water bath (the environment being heated).  Plug in the main power cord, and voila!  The PID controller will start to adjust the heat to reach the Set Value (SV) temperature.  Adjust the SV by using the up and down arrows on the PID controller.

We use our universal controller to sous vide with a cooler!  Here are the parts we use:

  • 1000W bucket water heater (Amazon). 
  • 16-quart (or larger) cooler (Local store or Amazon)
  • Ziploc vacuum (sous vide) pump and bags (Amazon)
  • Elite A800 aquarium air pump (Amazon)
  • Aquarium air tubing
  • 3-prong extension cord or surge protector

Note: The bucket heater may leech small amounts of lead into the water, but we think your food will be safe in a plastic bag (thanks to commenter salvarsan).  Be careful when disposing of the water.


The setup is very simple. We tied the end of the air tubing in a knot, and threaded it through the bottom holes in the bucket heater.  Then, we taped the air pump to the top of the cooler, and plugged it into the surge protector.

We placed the bucket heater inside the cooler, and plugged it into the output socket.  The controller’s thermocouple is left to dangle in the water.  The controller is plugged into the GFCI adapter, which goes into surge protector.

That’s it! We fill the cooler with water, flip the switch, and enjoy some tasty, juicy sous vide cooking! We hope you’ll have as much fun with it as we’re having.

Edit 3/23/2011: Added GFCI and clarified a little, thanks tward

Edit 4/2/2011: Removed bucket heater for food safety reasons.

Edit 4/4/2011: Fig 17 displays incorrect Pt100 lead order, thanks tward

Edit 4/6/2011: Bucket heater comment modified, thanks to salvarsan!

$70 DIY Sous Vide Universal Controller2011-02-22 01:17:00 GMT

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