A couple of years ago I saw this, a really cool beer cooler that utilises a Peltier device to cool the beer. I decided to build my own.First of all I gathered up all the stuff I needed:

  • A cafetiere frame
  • A GPU fan
  • A Peltier device
  • A toggle switch
  • A DC power socket
  • A holder for 8 AA batteries
  • Veroboard
  • Araldyte
  • Resistors and LEDs
I gathered up all this stuff over the last few months. Found most of the stuff on Dealextreme, Ebay, and Maplin.
So I started by getting some gluing done. I mixed up the Araldyte-esque stuff (I picked up some Chinese version) and stuck the fan to the base of the cafetiere frame, making sure that the shape of the fans were directed in the correct way to deliver maximum air volume to the Peltier device. The fan was positioned such that the air would blow upwards from the base then out the top.

Pro-tip. Be very careful where you place the glue. When I put the fan down, there was glue spread out all over the base, and it ended up sticking to the vanes. I had to keep moving the fans and scraping the stuff off them as it solidified. This still may cause problems, but we’ll see.

Next up was the DC socket, and I placed that just underneath the handle using the Not-Araldyte.

Once all that was done, I began work on the second stage of the circuit, which consists of a potential divider. I needed this as the Peltier device requires 12 volts and the fan requires 5 volts. For this, I used two resistors: 100 ohm and 150 ohm. This would drop the voltage down from 12V from the power supply (which would directly power the Peltier device) to just under 5V, ideal for the fan. In this stage I also added a light-emitting diode to act as a power indicator,

 but also to ensure that the current was flowing only in one direction, coz I’m paranoid about potentially wrecking me stuff. Electricity can only move in one direction through a diode, and a diode will also drop the voltage by ~0.7V.

Next up was the first stage of the circuit, which is power and switching. Now, I’ve spent ages trying to figure out what switch I need and how they would go into the circuit. It was head-wrecking.

My original idea was to have a 3-way switch: one position to run the cooler off a DC input from a plug, another position to run it off the battery pack, and a third position which would act as both the ‘off’ position and the ‘charge if plugged into mains’. To get this to work I think I needed a single pole, triple throw switch (SP3T), but to be perfectly honest I haven’t a clue, and ended up buying the only switch I saw that might do the job.

Turned out that my switch had two ‘on’ positions, and one ‘off’. So I had to redesign the circuit to simply use either battery or DC input, without an option to charge. At the same time, this is probably for the best. Charging batteries on this cooler could result in the batteries overcharging and becoming damaged, and issues with polarity between charging and powering the cooler meant complications resulting in a load of extra diodes and stuff. Messy.

Once I had the circuit ready I then worked on wiring up everything and sticking it to the frame. I had a rough idea of how I’d lay out the stuff on the frame, but it was also partially a matter of just seeing what worked as I went along.

I now have to power this bad boy up, and figure out which side of the Peltier device is the cold side before sticking it down.

Oh yes, the Peltier device. This thing is made of two layers of metal, a different metal on each layer. When a voltage is placed across the device, once side pulls heat from the other, resulting in a hot side and a cold side. Obviously, I want the cold side to face up towards my delicious beverage, with the hot side facing down to fan where the excess heat will (hopefully) get drawn away.

I hope to test this over the next few days, so I’ll keep this post updated!