About 18 months ago a Peltier Effect fridge we had packed up so I broke it apart and stole the interesting bits. The most interesting thing in it was the Peltier panel and, after thinking about checking this out for a while, I finally got around to it.
The aluminium heatsink is around 14cm x 18cm and has a solid base 8mm thick – that should dissipate heat nicely then!
The Peltier panel is (presumably) 8cm x 8cm and behind the heatsink. I’m using waterproof Maxim DS18B20 temperature sensors mostly because they’re well insulated (by definition) and have all the necessary cabling without me having to faff about. As you can see, I have one on the “hot” side of the system and one on the “cold”.
From the (little) reading I’ve done, I expected this to need a fair few Watts to work so it seemed like a job for the new bench PSU. Rather than cart that across to the other side of my study, where my PC desk is, I dragged out a Raspberry Pi and an Arduino Uno. I have a network cable handy on my work desk so it’s easy enough to ssh in and do things remotely from a few feet away.
That is a spot of blood on there – those heatsink fins are bugger sharp 🙁
The fans are underneath and are placed to blow air through the heatsink fins. There’s not a lot of clearance on the desk so I don’t think the airflow would be that great. In this configuration I managed to get the hot side at 29.5ºC and the cold at 4.5ºC – a difference of 25ºC between the two. That low temperature isn’t much to write home about – I was effectively trying to chill the whole room though.
It was getting a bit late last night at this point so I couldn’t be bothered writing the few lines of Python needed to capture the sensor data for plotting. I knocked that together this morning and then rearranged things to use a smaller “chiller” volume and to put the hot side on top for better cooling (hopefully):
On startup, current draw of the panel + fans is around 4.5A:
This drops away, eventually settling down to 3.88A
So we start at around 53W and drop to around 47W after 10 or so minutes. I guess that makes this a “50W” panel then. So, how did we do this time…
We reached -6ºC after about 30 minutes with the heatsink reading around 27ºC. That’s a difference of 33ºC between the two sides – I suspect the smaller volume surrounding the cold side made most, if not all, the difference.
So that achieves my goal of having a play with a Peltier panel. I didn’t blow anything up (the bench PSU safely limited the current when I tried it at 5V!) I guess if I want to cool a small space down and I’ve got 12V 5A to hand then I can dig this out again, otherwise I can’t say I’ve got any real use for it 🙂
The DS18B20 sensors really are a doddle to use. Being able to run multiple sensors off one pin is always nice – I could have done all of this without the Arduino, interfacing these sensors to the Raspberry Pi is well documented and not at all difficult. Old habits die hard though, I know the Arduino Uno “just works” and I can easily power it, program it and interact with it from the Pi. I guess I’ll get another Gertduino soon which will give me the best of both worlds.