Introduction: Universal Controller for Sous Vide Cooking

A while ago we built a $50 dollar sous vide machine to start messing around with sous vide cooking.  We loved it, and it has been 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.

Again we've avoided soldering anything, which simplifies the construction considerably.

You can check out some recipes and more DIY sous vide advice at our blog. The details in this instructible are posted there as well.

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.

Parts: Hardware supply:
  • 2 foot air conditioner extension cord
  • 2 foot 12 gauge wire
  • 1 foot 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. Now, strip the three wires on both ends by carefully squeezing the scissors at different angles on the cord until the insulator is detached, less than ½ inch should be bare.

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 by a half inch. Strip the ends to expose the copper wire. Choose ring terminals 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 before--- 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.

Step 2: More Power

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). 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. Then put the combined bundle in the other end of the butt connector, and crimp tightly.

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). 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.

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 3: 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.

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. 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 again.

Finally, we must connect the SSR to the heat sink. 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 4: PID Controller

Now connect the two ring terminals on the PID power cord to PID controller connectors 1 and 2. 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.

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. 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 5: Play!

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). It has been suggested that this heater is not safe for food use.  For now, we recommend a cheap rice cooker.
  • 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
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 controller. The controller's thermocouple is left to dangle in the water. The controller is plugged into the 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.


djsnowman06 made it!(author)2014-02-28

come on man... a large pvc box is like 8 bucks . im an electrician. if this is in canada i know its a CEC nightmare. if isnt im still quite sure its against code ... this is not how to do this.

mrkrog made it!(author)2013-01-10

Here’s a hint for anyone shopping for parts. Lowe’s sells a cheap 6 outlet power strip. My local store sells it for a bit under $3.50. If you take it apart, you get a 3 foot grounded power cord with 14 gauge wire that can easily handle 15 amps. As a bonus, it also includes a lighted switch that also functions as a circuit breaker.

For a little more money, you can get a 5 or 8 foot version. If you cut off some of the cord and strip off the outer insulation, you get some very good wire you can use for connecting your components. (I bought the 5 foot version and didn’t have quite enough wire for my rig. You may want the 8 foot version if you take this route.)

mrkrog made it!(author)2013-01-10

I just finished building a sous vide controller using a JLD612, a PT100, and a rice cooker. As soon as the probe went into the water, the temperature reading started jumping all over the place. I soon figured out that it would go crazy any time the probe contacted a grounded appliance. (My non-grounded crock pot, for example, didn’t cause any trouble.)

Some PT100s have a metal braid around the cable. If you have one like this, you should add a wire that connects the braid to one of the non-red (usually blue, yellow, or black) wires coming from the PT100. (All 3 PT100 wires still need to be connected to the temperature controller.)

My PT100 is a cheap unshielded version. (No metal braid around the cable.) So, I solved the problem by connecting a non-red PT100 wire both to ground (the green wire in the power cord) and the temperature controller. Now the temperature reading is perfectly stable.

I hope this information helps somebody.

devineDIY made it!(author)2011-06-20

That is a wee bit dangerous leaving the AC exposed like that, no?

Ouch!? :c}

abefetterman made it!(author)2011-07-24

We have insulating tape over everything, so nothing is exposed per se. But my roommate was not happy with the prospect of running this contraption without supervision.

Garadin made it!(author)2012-06-09

In my experience, I found that rubber hose, sealed with rubber cement or hot glue, makes an excellent insulator for wiring. I used some from an auto parts store that is used to replace broken fuel lines. 1: It keeps everything neat and tidy, and 2: as long as the spots where wires are coming out of the hose are sealed properly, it is extremely water-resistant (and durable). This tip should reduce the possibility of accidents involving exposed wire.

Belana made it!(author)2012-06-08

No way!! , great!! Do you think I could use it in my small table top glass fusing kiln?

mosman made it!(author)2012-06-08

Hi Guys,

Thanks for this great instructable. We made this a couple of weeks ago and have been having a great time sous vide'in ever since.

However, we have run into one issue. We purchased the bucket heater you recommended above. We needed it as we are practising for a 150-200 steak dinner. When we plug the heater into our controller we get a 3-4 degree temperature swing on the PID. The heat maintains (even over 48 hours) but the display bounces 2 degrees up, 3 degrees down, 1 degree up, 2 degrees down, etc.

We also bought the coffee urn you recommend on your site and have no problems with PID reading there. It is directly related to the heater. Have you experienced this? Any ideas on how to remedy the situation?


Mindmapper1 made it!(author)2012-01-06

I like your idea and for me it is a good starting point. However as with other comments the construction shown is electrically very dangerous. Water and electricity do not make for a good combination. I agree with your room mate about not running this without supervision and then the other part of me says don't be anywhere near it while it is on. Electrical connections twisted and taped are NOT SAFE on mains voltages. All connections should be secured with solder or better still through terminal blocks. Might be sensible to fit an RCD trip on the plug.

Bucket heaters are not designed for food use so personally I would not use one.

dgingrass made it!(author)2011-12-04

Any suggestions if the pt100 thermocouple has one red and two blue connectors??

abefetterman made it!(author)2011-12-05

I would try the two blue on 8 and 9, with the red on 10. You may need to switch around the 8 and 9 blue wires for higher accuracy.

rszabo1 made it!(author)2011-10-17

I'm basically making my own PID controller from scratch. I'm still not sure exactly how to tune it but I'm thinking that I can this with a very similar SSR and a different thermocouple. Any advice?

MikeQueenCreek made it!(author)2011-04-10

Great instructable, I have been working on getting one of these going this weekend. I bought the same SSR you used - bought two of them actually - and can't get either of them to work with the controller. I even tried plugging the DC into an old laptop charger I have that outputs 19v DC... Still nothing. Does the LED on your SSR turn green when it is functioning?

abefetterman made it!(author)2011-04-12

On mine the LED turns red when the power is switched. Try switching the polarity (the wires going to 3 and 4), and check that the voltage you apply is within the range marked near "input" (mine is 3-32 V). You may check that you are really getting a voltage across the terminals using a multimeter.

If your multimeter results are ambiguous, I would get a fresh 9 V battery and a 9V battery header, and attach the two outputs to 3 and 4 (black to 4, red to 3). If that doesn't light up the LED, the SSR is broken.

Good luck!

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