home made Peltier cooler questions

[graham.hobart (Graham stevens)]

Greetings, I took my nearly finished home made cooler out tonight to see if the bench test temp drop was the same when taking darks.
It seems not to have made much difference to the EXIF temperature so far, and I am wondering if the fact that I didn't do the aluminium box/washer to tripod mount hole metal connection thingy that Gary Honis does with his mod would make the difference. My inside box sensor is dropping in temperature but the EXIF temp has stayed the same. You can see by the picture that it is very much a prototype, ungainly thing that it is. It is also quite heavy with the two fans plus large heat sink.
In forty minutes got a 5 degree drop below starting temperature but as I said before the EXIF has hovered around 24-25'c which was the same as when it started. I assume the plastic camera body is insulating it better than I thought.
Any tips?
Graz from Taz.

[rcheshire (Rowland)]

Start again.

Hi Graham. Did you get to the bottom things?

Bert, (avandonk) has successfully used a cooler, from what I understand. Search the DIY section for his mod. Might help.

[wasyoungonce (Brendan)]

Hi Graham this can be a difficult thing to appraise from afar.

Thermal efficiency and energy (cooling) conservation is everything in a cooler box.

I see you have what looks like screws sticking out into the air...these would bleed cooling efficiency somewhat. Also orientating the outside HSF so the fins are vertical may help a little. You may be able to fit a bigger fan to the hot side as well?

I found that with my camera in cooler box it took around 39 minutes to reach ~20 to 25 degree C drop (down to -5C) with a 48W peltier. However this blew out to around just over an hour when I placed the box onto the focuser. I had previously been insulating the box nose piece but placing it all on the the DT really killed system efficiency.

I found if I wrapped as much insulation I could fit around the focuser DT/nose piece helped...but the cooling efficiency was effected and takes around just over an hr to reach the above and at best now cools to ~-1~-2C.

The Camera body is a real issue as you mentioned, but in general I did find the EXIF followed the box temp...with a lag of course...but not as you mentioned. You stated your box dropped 5C in 40 mins? This sounds as if you have efficiency/peltier issues...aka not enough cooling power, efficiency losses etc.

Have a look at my Picasa DSLR cooler box and the DSLR yahoo mod site by Gary Honis. (although you may have seen this site).

Hope this helps a little.

Brendan

[Grimmeister (Anthony)]

Hi Graham,

I think your issue looks to be insulation (unless you have this inside the box??), I had quite pleasing results with my Camera (Canon 600D) in my first Gary Honis Clone (except that it sheared out the metal in my T Adaptor) so I am doing Mark II of the cooler box.

Mark II moved the Peltier cooler to the rear of the box and changed the insulation to white foam (I used blue sealed cell foam in the first box and it just didn't keep the heat out) I used a wider aluminum bracket from the cooler to the camera mounting hole and a blower to move more air around the box and keep an even temp throughout.

I have two pictures of Mark II still being built (Ignore the chunks of foam as the glue is still setting before I can cut it off and sand it down) as well as two 10 minute dark frames, one cooled in the first box the other not cooled at all, you can see a big difference in the hot pixels.

I agree the plastic of the camera body does limit the transfer of heat out of the chip however when the box temp is ~4-5'C it still makes a hugh difference.

As a side I am using the same Peltier as you, looks like it was from a Dick Smiths portable fridge for $29 if I'm not mistaken LOL. So this should get you similare results if done right.

You have my details already so if you want more info just give me a yell.

Cheers

Anthony