In this project, I’ll walk you through how to make some self warming earmuffs. These utilize TEC/Peltier units to warm themselves. The device is pretty simple, and only requires some simple soldering skills.

It’s been snowing pretty heavily in my area lately, and I decided that I wanted to make a pair of these earmuffs to stay warm, and I realized I had everything to do so.

Warning: if the earmuffs get too hot, switch them off immediately.

Materials

2x – TEC Units (Peltier Units) – What I used: https://www.amazon.com/ALAMSCN-TEC1-12706-Semiconductor-Refrigeration-Thermoelectric/dp/B0BBM77LHJ/ref=sr_1_6?crid=1BEP3MDFEWS1X&dib=eyJ2IjoiMSJ9.JzuYnJ4uJosKCz3U9Dx5vzUWK6_lezDnk9_AXJSQpFNhg8I_hs2n0KNfSQJOsk3BG1zO9a87cfwU1EHtzSgJUETNypCHdwekUic5qEYPJ8g67kqU0YoK6ooc26esUX5X0w3oUvkQRZXqjlT1hVgNF8YdKF0r9AYzjUk9lhagOefdXQzV6VCks7WagxHbB4HsjzX0fao-9mSgT_eg736T7WkUE3-VZGZx6ML1L_LWV2U.LFfUaBl1KO8xpdSVTdawdtCOS4Ts4_IGUJSNlM8eFDM&dib_tag=se&keywords=tec+peltier&qid=1738908948&sprefix=tec+peltier%2Caps%2C172&sr=8-6

2x – 9-volt battery housings (with switch) – What I used: https://www.amazon.com/Battery-Leads%EF%BC%8CWidely-Student-Experiments-Batteries/dp/B09XBKT1DG/ref=sr_1_2_sspa?crid=3S3N83YUTDSQ1&dib=eyJ2IjoiMSJ9.GTRMcv0e6wtcWwAItlMfWXJ46qc7vFtPRWHPctaEskl04JO99-c1CXb91BO52n1cPTPImNqXMOUqFnZlp92XAQToQqYGIwF9D1FaE3wZS9GoDT6syQ3JdIvBrX7s-PYDi7lncph5rxYHhcIiTRp6vTWmwGvxWZXEcNYgwoSIeWK_gwSimA9zaH1EpCwU_IkdBN4rhSE3Knbn_upUEsWECALQAHpfJGeiwo7rFFHlC2A.nZbmU6kLZ38qCMXDoNGcSXM9-ykO5B0yHcooukgTSaM&dib_tag=se&keywords=9v%2Bbattery%2Bhousing%2Bwith%2Bswitch&qid=1738909047&sprefix=9v%2Bbattery%2Bhousing%2Bwith%2Bswitch%2Caps%2C183&sr=8-2-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&th=1

1x – Thick Earmuffs -- https://www.amazon.com/Ear-Warmers-Colors-Earwarmer-Earmuffs/dp/B076V5XH34?ref_=ast_sto_dp&th=1&psc=1

2x – 9v Battery

Tools

1x – Soldering iron (and solder)

1x – Scissors/Cutting Tool/Knife

3d printer

1x -- Sewing Kit

Other things

2x – Heat shrink wrap

Tape

And whatever cutting and marking utensils are needed

Some info for you:

Thermoelectric coolers, often referred to as Peltier modules or TECs, are pretty cool devices. When powered on, they will become hot on one side and cold on the other. It achieves this by moving heat from the cold side to the hot side.

Most of the units you buy on Amazon are rated for 12v, but you will be able to get away with powering them at 9v, it works decently well. If you have everything to use 12v, go ahead, but be wary about wiring.

The reason I say this is the same reason we use compression-refrigeration loops in fridges and A/Cs instead of these little guys: they pull a boatload of power. I only used these specifically because I had nothing else at home. If I were you, try to use a heating element or heating pad from Amazon or SparkFun.

First off, you’ll want to 3D print the TEC Mounts that fit into the earmuffs. I printed in PLA, with standard settings for the Bambu LAB P1S, but with 7% gyroid infill. It doesn’t really matter what filament type you use for this.

I used AUTODESK Fusion 360 for this project to design the TEC Mounts. I linked the .f3d files below.

Next, use your knife to make two slits in your earmuff’s pads to put in the TECs. Make sure they are big enough!

Checkpoint! Touch the leads of your TEC to a 9v battery. Does it heat on one side and cool on the other? If not, replace the TEC.

While checking the status of your TECs, feel which side gets hot and which side gets cold. Label them with pencil or Sharpie.

Next, insert your TEC into the 3d printed mount. Then, thread its wires through the mount’s cap. (Make sure the Hot Side of the TEC is touching the indented part of the mount and the cold side is touching the vent grille side.) Snap the cap onto the mount. (In the picture above, the cold side faces the camera).

Make a small cut on the very top of the EarPads, near the stem that goes over your head. This is where you will thread your wires.

Then, you need to thread your TEC’s wires into and out of the earpad. After wires are managed, squeeze the TEC and TEC Mount into the earpad. Do the same for the other pad, too. You may need to dig out some stuffing that’s in the earpads.

As for the batteries, we are using two separate 9v batteries instead of stringing them together because we will utilize the switches on each battery pack to turn each ear heater on or off. First, take out any batteries already in the battery packs and switch them off. Then, with the wires facing toward the earpads, tape and stick the battery pack to the top of the earmuff stem. You can alternatively use super glue. Make sure to tape it down in the orientation in the picture to ensure access to the battery access door and the power switch. Also, make sure you tape it in without the door on the battery holder installed, so you can easily replace batteries without unraveling the tape.

Next, slide some heat shrink wrap down your TECs wires for later.

Break out the soldering iron and solder together the TEC ‘s wires and the battery’s wires. Use an ample amount of solder and make sure the joint is strong.

Pop in some 9v batteries and test the TECs. Do they work? It may take up to 5 minutes for heat to be noticeable without putting the earmuffs on your head. If it still doesn't work, check your soldering, and make sure the wires haven’t snapped off of your TEC or battery pack. (If that’s the case, replace said part and redo the steps above).

Use a lighter or heat gun to shrink your heat shrink wrap around your solder joint. Be wary not to burn the wrap, though.

Sew up any cuts or slits you've made in the process of making this. It should look like the image when you're done. Be safe with needles, though!

Enjoy being the cool kid, because you're already done making these super cool self warming earmuffs! If you have any slack wiring, tape it down. These will take approx. 5 mins to warm up, and are perfect for cold weather.