Personal Cooling Device - Mini Wearable Cooler Using Peltier Module

This is a lightweight wearable device intended for personal cooling, originally developed as part of my bachelor thesis. The project focused on the creation of a prototype device based on the thermoelectric (Peltier) effect, aimed at applications in wearable technology — particularly for treating sports injuries and similar use cases.

The thesis was titled: "Development of a prototype thermoelectric cooling device for textile-based applications."

In this Instructables guide, the textile integration part is not included, as it is not essential for the core cooling functionality.

If you have any questions or encounter any issues, feel free to contact me via email: petar.ubavic@gmail.com

Electronics & Thermal:

1. Peltier module: TEC1-12706
2. Heatsink: ATS-54400W-C1-R0
3. Fan: MF40100V2-1000U-A99
4. Custom made PCB
5. ESP32 DevKit V1 (check pinout)
6. MOSFET: N-channel IRLML0030 - 3 pcs
7. Schottky Diode - SMA case (SS14) - 2 pcs
8. Schottky Diode - SMC case (SS34) - 1 pcs
9. 40 Pin Header Female Socket
10. Resistor 0805 10 Ohm - 2 pcs
11. Capacitor 0805 12 uF (Voltage 10V or more)
12. USB-A to 2 wire cable
13. USB-A (or USB-C) to USB-A cable (1m or more length)
14. 2 pin PCB 2.5mm pitch screw terminal - 4 pcs - Optional but recommended instead of JST XH if you don`t have appropriate crimping tool
15. JST XH 2 pin PCB connectors - 4 pcs - Optional
16. JST XH 2 pin female connectors - 4 pcs - Optional
17. Pins for JST XH connector - 20 pcs - Optional
18. Resistor 0805 100 kOhm - 2 pcs - Optional
19. Resistor 0805 47 kOhm - Optional
20. Capacitor 0805 220 nF (Voltage 6.3V or more) - 2 pcs - Optional
21. 100 kOhm NTC Resistor - Optional
22. Small switch - Optional

Case & Mechanical:

1. 3D printed case out of PLA or similar material
2. Velcro tape/strap or something similar - to tighten the device onto the body
3. M3 Threaded Inserts - 2pc - Optional
4. M3 x 6mm Screws - 2pc - Optional
5. Some super glue or hot glue

The whole device will work according to this schematic.

The Gerber files for the PCB ordering are provided on my Github -> Electronics -> PCB Gerber -> PCBv2.zip

PCBs can be ordered via many manufacturers like JLCPCB, PCBWay etc. For the JLCPCB - just drag-and-drop PCBv2.zip file onto their website and make an order.

Now solder components onto the PCB according to the schematics and photos provided - you can leave R1, R2, R3, C1, C2 and J3 unpopulated (you don`t have to solder those components). The device still will work as intended.

First start soldering smaller components, then go to the bigger ones, and as very last solder the connectors/screw terminals.

Solder together both pads (make solder bridge) of the SW1, or if you like, you can connect the small switch onto those two pads.

Instead of 2 pin JST XH connectors which are shown on the photos of the PCB as well as on the schematic (J1, J2, J3 and J4) you can use 2 pin screw terminals with 2.5mm pitch.

Instead of soldering ESP32 onto the PCB directly, solder female pin header onto the PCB, then just plug ESP32 into the slot (be aware of the orientation and pinout).

When you are finished with the soldering, connect the USB-A (two wire) to the J1 (marked BAT on the PCB in the top right corner according to the photo) make sure to match the polarity correctly - the positive wire goes to the '+' pad marked on the PCB. If the polarity is reversed, the device will not function (it won't be damaged, but it won't work either).

Now connect that USB-A connector to your phone charger/powerbank/laptop with appropriate cable (USB-C to USB-A or USB-A to USB-A - depends on which charger you use). Would be preferred that source have 2A or more of current capability.

If the ESP32 lights up, flashes, or gives any sign of life — it’s alive and functioning!

Disconnect the USB power cable.

NOTE: If you're not going with the PCB option and prefer using a perf-board, that's totally fine—just replace the IRLML0030 (SMD) MOSFET with a IRLZ44N (through-hole) MOSFET. In that case, there's no need to connect two in parallel. Aside from that, the entire schematic remains the same. Also, it's possible to replace the SMD Schottky diodes with through-hole versions as well.

Just keep in mind that in this case, you’ll need to pay close attention to the perf-board dimensions, as the space available for the electronics is very limited.

Flash the code that is provided onto the ESP32.

The code is written in Arduino IDE, which is also used to flash the code.

The support for ESP32 does not come by default in Arduino IDE, so if you don`t have installed packages etc. for ESP32 in Arduino IDE, follow this tutorial.

This code includes support for adjusting the cooling intensity via Bluetooth, but you can ignore this part, as it will not be used or discussed further. Note that it only allows decreasing the cooling, not increasing it

Now 3D print the parts (.step files of every part is provided in supplies section). There are 3 files:

1. Peltier_case v2 part1_main_case.step - or main case for short
2. Peltier_case v2 part2_top_cover.step - or top cover for short
3. Peltier_case v2 part3_door.step - or door for short

Optionally, you can add two threaded inserts into the main case (from above). This will allow you to screw and unscrew the top cover from the main case as needed, and many more times than without inserts - without them, the screw will eventually damage the plastic.

Thread a Velcro strap underneath the handles on the top cover, so the device can be secured around your arm or another part of the body. To prevent the strap from slipping out, add an extra layer of Velcro between the two handles that acts as a stopper. This piece should be fixed in place—either by stapling, using super glue, or another strong adhesive method. You can also use elastic material instead of Velcro if preferred.

A complete 3D model of the casing is provided in this section.

First, place the fan into the case and route its cables to the electronics compartment at the back of the main case. Avoid leaving the cables too long, as space is limited.

Second, attach the heatsink to the Peltier element, making sure to correctly identify the hot and cold sides of the Peltier. Usually, the hot side is the one with the module's label, but you should always double-check before assembling. To verify the cold side, carefully hold your fingers on both sides of the Peltier first, then briefly apply a low voltage (around 5V) and feel which side cools down. The test should not last longer than a few seconds (about 5 seconds) to avoid damaging the Peltier. Place the hot side of the Peltier against the heatsink, ensuring the heatsink fins are oriented as shown in the picture - in the way that fins are not blocking the air to exit thru the front part of the main case, so that air can flow freely and efficiently remove heat from the heatsink. Also, be careful not to leave the cables too long.

Third, insert the assembled Peltier element and heatsink into the case from the bottom side. Use the two small slots ("teeth") on the bottom of the case to guide the Peltier wires through to the electronics compartment. These slots will also help hold the assembly in place inside the case. Additionally, it is recommended to apply a few drops of super glue between the Peltier and the heatsink, on the edge farthest from the electronics compartment. Also, apply a few drops of super glue between the heatsink and the case (again, on that farthest edge) to secure the heatsink to the enclosure. All of this should be done from the bottom side of the case.

Make sure that the Peltier module protrudes 1–2 mm below the case, as shown in the photo, to ensure good contact with the user’s skin later.

Fourth, place the soldered PCB into the electronics compartment. Make sure to route the USB-to-two-wire cable through the small window on the door part. It’s usually necessary to thread the wires through the window first so that the USB connector stays outside the case.

Then, connect the Peltier and the fan to the PCB as labeled:

1. The fan goes to the second connector from the top (positive pin is marked with a + sign on the PCB, as seen in the “Make Electronics” section),
2. The Peltier goes to the third connector from the top, negative pin is marked with a – sign.

Negative wire is black wire on the Peltier and fan, and positive wire is the red one.

Depending on your setup, there are several ways to make the connections:

1. If you’ve soldered a JST XH connector, simply plug the female connectors in.
2. If you’ve used screw terminals, tighten the wires in place using a small screwdriver.
3. If you haven’t done either, solder the wires directly to the PCB pads.

Fifth, assemble the full enclosure: attach the Top Cover and fasten it to the Main Case using two M3 screws (or glue it using super glue or hot glue). Then attach the Door, which should snap into place with the rest of the case. However, since it might fall off during handling, consider applying a bit of hot glue or a drop or two of super glue to keep it in place.

That’s it! Now plug the USB cable into a power adapter and enjoy cooling your injury! 😄

NOTE: The device can not be powered through the ESP32 connector. Use the USB-A connector to supply power.