Peltier Wrist Cooler

A wrist mounted device which helps you stay either cool or warm. The switch on top changes the polarity of the peltier-element inside, so the device either cools or heats you.

How it works:
The bottom of the device houses a peltier-element. When power is applied to this, its surface gets either hot or cold (depending on the polarity). By mounting this at the wrist, we take advantage of the body's circulatory system to spread the heat or cold through the body. The other side of the peltier is connected to an aluminum heatsink with a fan which blows air through it. When in cooling-mode, waste heat will get blown out of the sides of the device. When heating, cold air will be blown out. The box on the rear of the device contains electronics for supplying the appropriate voltages to the peltier-element and the fan, and also has a micro-USB socket.

Quick points:

• Powered by micro USB.You can use common phone chargers, USB power-banks, or even a computer USB-port.
• Low power usage: about 400mA @ 5V. Most powerbanks should be able to power this thing for hours.
• Currently better at cooling than heating. When heating, it's trying to take heat from air at maybe 20C and put it into skin that's about 30C, which is difficult for the peltier-element. When cooling this temperature difference works to our advantage instead.

Electronics details:

• Input voltage from Micro USB is 5V.
• Uses an adjustable boost-converter to power a 12V fan. The fan is run at less than rated voltage to keep the fan quiet.
• Uses an adjustable buck-converter to power the peltier-element. The peltier is run at a really low voltage, 1.7V in my case (uses about 1 to 1.5 Watts of power), to keep efficiency high, and to keep the device touch-safe.

Instructions are being made.

Warning:
Do no supply too much voltage to the peltier-element. The surface-of the peltier element might get too cold or too hot, which can result in frostbite or burns!

Suggestions, improvements or outright forks are welcome. I want this device to be as good as possible.

Update 2023: I uploaded Fusion 360 files for this project. Both the version shown in photos, and a slimmer version for a 7mm fan and 11mm heatsink.