Sous Vide temperature controller for $50-$100

Picture of Sous Vide temperature controller for $50-$100
Update June 6: Added step for using a bucket heater and cooler.
Update March 8: I added pictures for the fuse and switched to using a SSR.

This will show you how to build your own accurate temperature controller for cooking with sous vide.  How much you spend depends on what you use for a heating element.  This controller is accurate to 0.1° C and is able to keep a steady temperature within 0.2°C of the desired temperature.

First I need to give credit to Scott at Seattle Food Geek.  This instructable is inspired by his genius DIY sous vide.  Check it out for an alternative to mine at

My controller is a little more generic than Scott's in that it can use any electric heat source to keep the water bath at a constant temperature.  I use a cheap crock pot but plan on using a bucket heater in a cooler when cooking for large parties.

Let me know if there are any mistakes of missing steps and I'll try to fix them asap.
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Step 1: Parts list

Picture of Parts list
Here are the parts you need:

1) PID controller.  I got mine on Ebay for ~$35 (including shipping).  Most controllers will do but avoid ones that have a built-in relay--the relays usually aren't rated for the current your heater(s) will use and will blow out your PID controller.  The wiring for this instructable assumes your controller puts out 12v to control an external relay.

2) Aquarium pump for water circulation.  You don't have to get too fancy--it seems that most pumps can handle the heat for common sous vide cooking (< 70° C).

3) 10+ amp electric relay.  I originally used a mechanical relay (see pictures) but it eventually wore out.  I've updated the build with a 10 amp SSR that I got used on EBay for $4 (many people on Scott's page are using 25 amp SSRs).  If you don't know anything about SSRs make sure you get one with DC control voltage and AC output voltage.  This one will do:   Depending on what you're using for a heat source you may want to get a heat sink.  See my discussion in the step that installs the SSR.

4) 10+ amp switch.  I bought a light switch from Home Depot like the following (mine was cheaper): .  Get a rectangular one because it'll be easier to cut the holes in your enclosure.

5) 10+ amp dual socket like this one: .  Again, get a square one because it'll be easier to install.

6) A 3-prong power cable with bare leads.

7) A PT100 temperature probe (thermocouple).  Get a three-wire probe because it'll be a little more accurate (and because I don't know how to hook up a two-wire probe to the PID controller).

8) Some sort of plastic enclosure.  I went with a junction box because they're easy to cut with a Dremel and very sturdy but at $11 it's overkill.  You can get a plastic acrylic box for ~$4.  I'd advise against a metal box to avoid electric shorts.

9) 10 amp fuse and fuse holder.

10) Various wires and screws.  For doing the AC power wiring you want wire rated for 10 amps.

11) 8-screw terminal block.

12) Electric heat source.  A crock-pot works well.  Make sure you get one that turns on with a mechanical switch--the controller is going to continuously toggle the power to the heat source and you don't want a digital crock pot that has to be reset after every power cycle.  I got mine at a thrift store for $15.

Not required but handy:

1) An outlet wallplate to use as a template when cutting your enclosure.  (Like this: .)

2) LED for indicating when the heater is on.  Most PID controllers have a little light but I wanted mine to be obvious.  I got an LED assembly with a built-in resistor.

3) Male and female three-wire audio jack for hooking up the PT100 thermocouple.
ao'dell1 made it!11 months ago

Great add! $78 total.

Deeg (author)  ao'dell111 months ago

Good looking build! Thanks for the pictures.

pb4041 year ago
Wondering if you think this would work. It's a waterproof probe on a thermostatically controlled power outlet. Just add the aquarium pump...
Deeg (author)  pb40412 months ago

I would think that would work but it's relatively low power (6 amps) and it's for 220 vac. The other question would be how accurate it is.

SQWIB1 year ago

Awesome build, Working on one now with the JDL612 but not sure how to program it.

I have the set value set but the heaters never shut off If I hit autotune it works fine but I have to do this every time I set a new temperature and it takes an hour or so, any tips you can offer for settings, the manual is useless to me.

Deeg (author)  SQWIB1 year ago

Thanks SQWIB. Unfortunately I don't have much help for you since I've never used the JDL612. You could try posting a question on the original Seattle Food Geek article because some people there have used it. You might not get an answer, though, because it looks like the comments have been taken over by spammers. =/ Good looking build, btw!

Deeg (author)  Deeg1 year ago

The SFG link might be helpful, no? Here it is:

As an electrician I must tell you that it is against code to switch the neutral sid of the plug. Split the brass side/ labeled black or hot. Tie the white directly thru and do all the switching on the black side
rkinch2 years ago
Why does everybody call the PT100 device a thermocouple? Isn't it a resistance temperature detector? The circuitry and troubleshooting are quite different for one versus the other.
mrkrog2 years ago
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.
fkan2 years ago
Great article. Thanks for sharing. I am a newby to electronics and wiring and have a dumb question. How do you connect a 3 wire PT100 to an audio jack? I thought the audio jack only has two wires. Thanks for a great article.
Deeg (author)  fkan2 years ago
hey fkan, I used a stereo audio jack which has three wires.
Mindmapper13 years ago
Another good starting point which has given me loads of ideas. I am thinking of adding a countdown timer to switch the whole lot off at the end of the preset cooking period, has anyone else tried this?
Deeg (author)  Mindmapper13 years ago
You could try using an outlet timer like this one:

Not necessarily elegant but easy and cheap. Just be sure it can handle the wattage of your heating element.
Hi Have built mine with a countdown timer which is excellent. I will be posting my design later.
freeworking4 years ago
Correct me if I'm wrong, but it looks like you have the switch connected to a neutral wire. I believe that, as a matter of safety, the switch should be connected to the live wire instead. The device will be functional as pictured, but in most every case it is a better practice to have the switch on the live or "hot" wire.
Deeg (author)  freeworking4 years ago
You may be right; I didn't pay much attention to the hot/neutral wires. I need to do a bit of rewiring so I'll check on that. Thanks for the tip. :)
FYI, It is a violation of the National Electrical Code to switch the neutral. The reason being that even with the switch off, power is still supplied to all of the components. If a short were to occur between the switch and the components they will come on, even when you don't want them too.
In addition, never cut or shorten/lengthen the leads on a thermocouple. They are calibrated at the factory. Changing the length of the lead wires changes the resistance which changes the output of the thermocouple causing an error (probably what caused yours to be off by 2.3 C).
devineDIY3 years ago
I would guess that one could plug many of the same model crock pots into a power strip that which plugs into the controller. Have to have the about the same amount of water and food in each, but it would be fully scalable.
devineDIY3 years ago
The outlet looks lice, but mounting it is a bit of a pain.

Another option:
Buy a 6 foot extension cord;
cut the female end off with about 1 foot of cord;
drill a hole for the cord;
add a simple gromet for strain relief and your done.

You already need the male end to plug into the wall.
jchen103 years ago
I've been looking online for a JT100 and i couldnt really find anything. Where did you get yours?
Deeg (author)  jchen103 years ago
That would be because I have a typo in my text--you want a PT100 thermocouple, not a JT100 (I'll fix this shortly). Here's one similar to the one I've been using:

Sorry about the confusion.
mpap894 years ago
i bought a relay but i'm having trouble hooking it up. I think i bought the same blue 10 amp one from radioshack. do the signals from the pid go to the "coil" pins then 120vac going to the normally open and the incoming 120vac to the "com" pin? thanks
Deeg (author)  mpap894 years ago
Yup, that's correct. If you have a multimeter you can verify that you're getting positive voltage from the PID that controls the relay..
mpap894 years ago
i'm trying to find the proper pid controller on ebay but it seems that almost all of them have 3A relays. should i get one with a solid state relay like this one:
I'm excited about this build. Thanks
Deeg (author)  mpap894 years ago
It looks like that PID will work. If I understand it correctly it has both an internal relay and output for controlling a relay (you can probably confirm that by requesting a link to the spec sheet.

You might want to look into getting a different thermocouple.  The 'K' type thermocouple packaged with the PID isn't as accurate as the PT100 (Wiki has an article on thermocouples here: and it's a little short, which will make it harder position in the water bath.  I've had good luck using this PT100:  (Note: It'll take at least a week to ship if you're in the US.)
aeray4 years ago
Excellent, and a hell of a lot cheaper than a commercial unit. Favorite'ed.