Introduction: Stay Warm This Winter: CPU Hand Warmer

Picture of Stay Warm This Winter: CPU Hand Warmer

In this small project I will show you how I repurposed an old AMD CPU to create a small, light and easy to use electric hand warmer. With the help of a small portable power bank this gadget can warm you up for around 2 and a half hours and can easily reach temperatures up to 60 degrees celcius.

Step 1: Watch the Video!

The video gives you all the info you need to build this thing. But I will also give you a few advises during the next steps.

Step 2: Get Your Parts!

Picture of Get Your Parts!

Here you can find all the parts I used during this build except the CPU. But you can find an old one very easily and cheap on Ebay.


1x Arduino Nano:

1x DS18B20 Thermal Probe:

1x 10k Resistor:

1x 5V Power Bank:

1x USB Cable:

1x Arduino Nano:

1x DS18B20 Thermal Probe:

1x 10k Resistor:

1x 5V Power Bank:

1x USB Cable:

1x Arduino Nano:

1x DS18B20 Thermal Probe:

1x 10k Resistor:

1x 5V Power Bank:

1x USB Cable:

Step 3: Download the Code for the Thermometer!

Here you can find the sketch for the thermometer that I used during the video.

Don't forget to download the necessary libraries:

How to connect the DS18B20 to the Arduino Nano?:

RED --> 5V


WHITE --> D3 (digital Pin 3)

Don't forget to put a 10k pull up resistor between D3 and 5V.

Step 4: Success!

Picture of Success!

Now you know how to build a small CPU hand warmer. But don't try to use it to keep your beverages warm. That will not work!

Feel free to check out my Youtube channel for more awesome projects:

You can also follow me on Facebook, Twitter and Google+ for news about upcoming projects and behind the scenes information:


SCStm (author)2017-01-15

what is this? how can ı find? can you send me this object's link?

SCStm (author)SCStm2017-01-15

I found it. its name its name is breadboard

Macinyash (author)2016-12-22

I have the same CPU as the video. Would you be willing to tell me which pins to connect the wires to. Thanks

종훈이 (author)2016-12-13

So neat.! This guy has innovative thinking on his brain!

Yonatan24 (author)2015-11-04

Why did you secure the wires with hot glue? This heats up...

Why didn't you use a resistor instead of the CPU, Resistors are 100% efficiency...

AndrewS435 (author)Yonatan242016-11-06

I used epoxy on mine and it worked great, plus it looks more smooth

devwatts5 (author)2016-01-04

thank you for making this project,i really love it,But i Am a begginer can you please tell me which pins i have to connect wires to i Really cant understand-My Cpu Is Intel pentium 4 3.86ghz 519k please help anyone...

AndrewS435 made it! (author)devwatts52016-11-06

These pins usually associate with old pentium 4's.

AndrewS435 (author)2016-11-06

Great project scott, only one issue i seem to find is that my cpu handwarmer sometimes dosent work, sometimes does! I've tried it in plugs and portable chargers and only sometimes it just dosent heat up at all, any ideas why?

Green gadgets (author)2016-10-20

This way better than the other one I saw where yu get a wire and solder if to a 9volt battery.

ahmedsidd (author)2016-01-01

what if I do not have an variable bench power supply? How should I measure the current draw

AhmedA352 (author)ahmedsidd2016-05-19

Use a 5v power supply and measure the current with a multi-meter .

watch his tutorial about it here:

devwatts5 (author)ahmedsidd2016-01-04


Waarvoorwiljedat (author)2016-01-04

How much power does it require?

PowellMade (author)2015-02-03

Cool could this be hooked up to a solar power unit?

Yonatan24 (author)PowellMade2015-11-04

Why not? It should work if the solar panel can supply enough current

gluvit (author)2015-09-19


yhdesai (author)2015-02-06


throbscottle (author)2015-01-31

Neat! You found a flat heating element that would otherwise be junk. I think the flatness is important - not like a resistor... Good work :)

Gr8Gr1000Pop (author)2015-01-29

couldn't find the like button but definitely liked it

jueljp (author)2015-01-28

brilliant, now I know what to do with a bunch of old Intel processors

boocat (author)2015-01-28

I really like this, never thought about it before. Now I'm going through all my tubs of bits and bobs! Thanks.

TSellers22 (author)2015-01-27

Hand warmers have been a hobby for the past couple of years, a couple of ideas on the same topic: Last year built some ski boot footbed heaters. Found that 3200mAh and 1A output are not sufficient to provide enough BTU, have been using a power bank that allows for 2A output and I use 4 3400 mAh Li-Ion cells for a total of 13,600 mAh capacity. It seems like the downside of electric is the weight. You'll get roughly 1 hour of burn time per 2ml of fuel from a fuel catalyst hand warmer, it seems like it takes about 46g of Li-Ion chemistry (EG, one 18650 cell), to provide roughly the same.

With the fueled hand warmers, I found a viable source of carbon felt to use for reservoir material replacement, and have started to replace the cotton batting in the Chinese hand warmers with a laminar insertion of tri folded carbon fibre batting material made from 90% polyacrylonitrile and 10% petroleum pitch. No more burnt cotton batting right under the catalyst head. (That burnt area presents an obstruction to the movement of the fuel vapours from the reservoir to the catayst.) The result is a noticeable improvement in hand warmer performance: the units burn up to 25% hotter, and last longer, probably because they absorb and retain more fuel. Another plus: the ability to use cheaper naptha gas instead of Ronson fuel because the carbon felt is a better wick. And a big plus: odor emission characteristics. As you know, carbon is commonly used as a filter material. While the carbon felt hand warmers are still not odor free, there is a significant improvement in the smell the hand warmer that uses carbon felt emanates as compared to the cotton filled hand warmers. It is also possible to obtain better performing platinum catalyst material for the heads domestically if you hunt around.

boocat (author)TSellers222015-01-28

TSellers22 - Interesting reply. I enjoyed reading it. Write something in here. I look forward to hearing more from you.

sjane1 (author)2015-01-27

This looks like a pretty cool idea, what with a CPU being just about the perfect size for the palm of your hand, and already having that awesome very well engineered heat spreader on top. Plus even if you don't have a bunch of old CPUs lying around, you can grab old P4s for like $2 on ebay. Of course you don't actually need the probe and the arduino for this build, which you should probably mention up top, because without watching the video and realising that, it looks like it's going to be a more expensive build. if you want to check that it's not so hot that it'll burn you, then you can use any thermometer in the right range to do so, you might even be able to use your phone to do it. Or heck just keep a finger on it as it warms up until it stops getting any hotter or else gets too hot, or just touch it with a towel or something.

Of course for an even simpler build just buy one of those little 5V power banks and that's it, you're done.

...connect it to charge your phone and download a handwarmer app for your phone (yes they really exist - for android at least) obviously all they do is flog the CPU with makework calculations, but it makes for phone pretty damn warm, pretty damn quick. Of course this murders the battery but it's useful for a few minutes in an emergency, and if you've got a powerbank or it then obviously you'll get exactly as much heat out of your phone for a given capacity battery as you would from any other resistive element. (and you can potentially do some useful work with your phone's CPU at the same time, run folding@home or something for instance, maybe even mine some bitcoins lol.)

samwyze (author)2015-01-23

This would make a great heated bed for a CDROM based micro 3d printer!

GreatScottLab (author)samwyze2015-01-24

I never thought of that. But it surely sounds interesting.

Alpha_geek (author)GreatScottLab2015-01-27

I've been looking for a way of providing additional heating for one of my 3D printers, and I've also got a load of dead/dying PC parts lying about ... problem solved, thanks.

ibob4tacoz (author)2015-01-23

Actually, most CPUs tend to idle at around 35C, without the cooler, maybe a little higher. The thing is, the power is coming from a puny portable battery, not a (fill in PSU wattage here) power supply. Either way, at 90C, CPUs tend to bug out and throttle.

missioncode (author)ibob4tacoz2015-01-27

"Actually, most CPUs tend to idle at around 35C, without the cooler," What? in a computer and idle??? No way will they stay that low. Maybe if you were just sitting in BIOS, but even then I highly doubt that. If you are feeding any power at all they are going to heat up.

Tomahawk92 (author)ibob4tacoz2015-01-26

do you think I would damage the CPU if I hooked it up to a computer PSU for a couple hours at a time without a heat sink?

ibob4tacoz (author)Tomahawk922015-01-26

Well, it depends. Technically, you can't hook a CPU directly to a PSU, but even if, as long as you don't do anything with the computer, it'll sit pretty toasty, but won't damage it.

davide.bisio (author)2015-01-26

I do not understand why you wanted to destroy a CPU. With a resistor of 6.8Ohm 4W you would get the same performance. In fact you need to dissipate about 4W of power with a current not exceeding 1A:

5V / 6.8Ohm = 735mA = <1A

(5V) ^ 2 / 6.8Ohm = 3.68W

In addition it would be useful to add a MOSFET controlled by Arduino, to change via PWM and power dissipated and maintain the temperature at not harmful levels.

JohnS4 (author)davide.bisio2015-01-27

Many of us have old CPUs around that are not viable to use, due to it being outdated or replacement motherboards being overpriced.

Do you have a 4W 6.8 ohm resistor laying around or an old CPU? I had the CPU.

Landroo (author)2015-01-27

Since the product of of electrical resistance is always heat, why not use a resistor or a heating element? This project is a "Rube Goldberg" solution to a very simple problem.

Dashing Rainbow Dash (author)2015-01-26

not bad. being me though, i would use a power resistor instead lol

vonronge (author)2015-01-25

cool idea. add a warning though. 60 °C is hot enough to cause 3rd degree burns in about 9 seconds of skin contact, depending on which insulation you wrap it in (thermal conductivity)

AndrewD1 (author)2015-01-23

*by "this is cooler" I meant your instructable is cooler*

GreatScottLab (author)AndrewD12015-01-24

Thanks ;-). And your idea also sounds good.

AndrewD1 (author)2015-01-23

You can also use a peltier cooler, a switch and batteries as a simpler version but this is probably cooler

Depending on how warm you want it you could vary the voltage rather than using a micro controller

wliu3 (author)2015-01-23

I think for the cpu to reach 90C you need to actually power it up with the actual power pins but not a random pin that draws a lot less current.

bk-bear (author)2015-01-23

Well isn't the work temp of cpu like 90C or something you schould be able to make warner some way

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