Cat cooler Peltier redesign

I have been wanting to design a peltier cooler for my cat cooler. The Cat cooler is a great tool for cooling SCT's but it is not active cooling in real terms.

So I set about redesigning the system. I went out several months ago and bought one of those Dick Smith fridges. I ripped that apart and put the essential parts aside. ie like the heat sink, fan, peltier and cold plates.

I also went and bought a few accessories to fit it out. I picked up a square down pipe fitting with a round opposite end. Several banana plugs and ends, a soldering iron, some adapter pipes and some screws.

The image below shows the inside, where I jammed the cold plate of the peltier into the downpipe adapter and cut out a piece of ice cream lid to act as a buffer plate. You can see in the image that I have also fitted another small fan. This pushes air up the chamber toward the cat cooler. I found that I could not have the cat cooler directly in contact with the cold plate as the fan system the cooler uses requires some space behind it for it to work correctly. If you have it too close it will not blow air very quickly at all, in fact it hardly moves air at all in this position.

The image directly below looks down onto the heat sink and fan for the peltier. I simply inserted both heat sink and fan into the square end of the adapter.

When the cold plate is screwed to the heat sink it sandwiches the pipe adapter into place and it is all snug. You can also see that I have fitted some banana plugs and end which I have soldered the wires of the peltier and fan together. I deliberately used the banana plugs so that I could cut off the peltier if I just want to run the fan. Also it means I can pull the connection wire off when I want to transport the unit somewhere.

In the image directly above, you can see how the whole assembly fits together. The black tape is a temporary solution to the adapter that holds the cat cooler in place. It is quite sizable now but light enough to do the job. On the right of the image you can see the base end of the cat cooler coming out of the pipe adapter. I will complete the connections tomorrow. I need to work out how to fix it all together so that I can dissemble and reassemble for maintenance work.

Now to the real question, does it work. Well before the centre chamber and internal fan went in I would have said no. However now that I have made the mods it needed, I started it up and ran it for 15 minutes or so. When I first started it I put my hand up against the delivery end and felt how cold the air flow was. It was cool but not cold, when I returned in 15 minutes the air was very cold and was flowing really well out of the outlets. So the upshot is, this system works. I do have to test it out on my scope, but am sure that if I ran it for 40 minutes on a room temp scope outside that it would deliver better results than it did before.

I got the temperature monitor and I checked the cooler both with the peltier active and with just the lymax cooler working on it's own. With the peltier cooler and lymax going it was nearly 2 degrees colder than with the lymax working on it's own which was 1 degree cooler than ambient.

by Paul Haese