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1100D cold finger sensor cooling with TEC and water cooling

Gina

By Gina
in DIY Astronomer

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Gina

Gina

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Impressive stuff :) looks like another project to add to the todo list.

I would be interested in seeing some results of a stacked set of lights and darks with and without cooling to see the ultimate results of this mod; do you know of anyone who has done this test ?

Thanks

I guess you could compare my M51 images before cooling with those after but the trouble is, other things aren't equal. For a proper comparison it would meed two runs under the same conditions, one with cooling and one without. Problem with that is getting enough clear sky time.
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Gina

Gina

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Very nice work! Have you considered a small radiator instead of waterblock & heatskink combination? That would be a more efficient solution for removing the heat I would think... though I'm guessing you probably though that but are just using the parts you have.
Yes, I have a 120mm radiator and fan which I got since making up the cooling system with water block, heatsink and fan. This is working fine so I haven't bothered to change it. The greater efficiency of a radiator could well be of benefit in warmer weather but ATM the present system produces far more cooling than actually needed.
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Gina

Gina

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:):icon_salut:

That is a very noticeable difference! I'm planning on doing the filter removal mod on mine and might do this one too while its in bits now you've shown us all how.

Thanks!

You're welcome :) Good luck with your mods - just take things slowly and carefully :(
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SamAndrew

SamAndrew

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I guess you could compare my M51 images before cooling with those after but the trouble is, other things aren't equal. For a proper comparison it would meed two runs under the same conditions, one with cooling and one without. Problem with that is getting enough clear sky time.

I've had a look at that thread and will continue to follow as you get to do more testing. It will be interesting to see the results once you've sorted out the dewing.

As I suggested in Luís' thread, you could try running the water cooler out pipe around the focuser to warm the front of the camera slightly, I imagin the whole camera/flattener/focuser must be chilled relative to the surrounding air, so a bit of heat here will help.

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Gina

Gina

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I've had a look at that thread and will continue to follow as you get to do more testing. It will be interesting to see the results once you've sorted out the dewing.
I'm slowly working on it. There doesn't appear to be any hurry - the weather looks grim for several days yet - at least!
As I suggested in Luís' thread, you could try running the water cooler out pipe around the focuser to warm the front of the camera slightly, I imagin the whole camera/flattener/focuser must be chilled relative to the surrounding air, so a bit of heat here will help.
Yes, good idea, I'll do that :)
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Gina

Gina

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Stripped down the camera again this evening, added thermal insulation either side of the cold finger and put a DS18B20 temperature sensor in thermal paste on the cold finger next to the image sensor. Held in place with a drop of hot melt glue. Put the back on temporarily and checked it still worked. I'll open the back up again tomorrow and insert some silica gel bags.

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pete_l

pete_l

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That's an impressive comparison with 1 hour darks.

One thing that comes to mind - if the water cooled 'scope is kept in an observatory, would you need to use antifreeze instead of water for those cold winter days when the temp. is below zero?

I don't know how your pump / Peltier would react to antifreeze - hopefully the stuff is inert.

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Mr TamiyaCowboy

Mr TamiyaCowboy

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Stripped down the camera again this evening, added thermal insulation either side of the cold finger and put a DS18B20 temperature sensor in thermal paste on the cold finger next to the image sensor. Held in place with a drop of hot melt glue. Put the back on temporarily and checked it still worked. I'll open the back up again tomorrow and insert some silica gel bags.

i think just the insulation will have a marked effect in calming the misting problem.

maybe a test run without silica first when the candy floss sky goes away.

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Gina

Gina

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There was just enough room for a couple of bags of silica gel between main board and camera back. It's all back together with silicone grease in various gaps for sealing. I'm now going to take the camera back out to the obsy. I'll probably check it out with a lens on the local fields and trees, livestock etc. and see how low I can go before getting misting up.

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Gina

Gina

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Been running a test with the camera on the scope (ED80) pointing at a hedge a few fields away. No condensation so far and been running for some time at -9C. That seems to be the coldest I can get it with the present setup. Running the TEC at 5v reduced the EXIF T from 29C to -4C in a nice slow time. I'll check actual timings/temperatures later - the test is still running. I gradually turned the voltage up and reached -9C at around 10v. Increasing that up to 12v (the rated voltage) didn't make it any colder. The TEC absolute maximum voltage is 15v and I took it up to 14v and still got -9C. I guess it was just producing more self heating and no more cooling. Ambient temperature is 7C.

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Gina

Gina

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I'll set up the 120mm radiator and fan and see if that makes any difference but I really think I would only gain about a degree more cooling as the TEC hot side is only a few degrees above ambient it's only just discernible by touch. I could also improve the thermal insulation of the cold finger outside the camera.

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mindburner

mindburner

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hi

I have been trying to build a cooling chamber with some success. My metal work skills are not exactly stellar but the case came together ok, despite nearly removing two of my fingers. :hello2:

The main issue I have is the poxy peltier cooler I got from ebay. Well it just doesn't work well. I got a 50w unit which is pretty much useless. I have ordered a 100w one so I will see if it fairs any better. I wanted to ask what cooler you have been using Gina and if you get actual decent cooling from it.

some 'in progress' pics here

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Gina

Gina

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Mine is 50W 12v from ebay and I'm none too impressed by it's efficiency at anywhere near it's stated voltage. It seems to do almost as well at 5v as it does at 12v! I'm been thinking of ordering a 100W one too. Best mine will do with my cold finger setup is -9C with an ambient of 7C. ie. a temperature reduction of 16C. I want more than that.

Actually, having looked at the list on ebay I think I'll go for a pair of the 136.8W 12v ones at £11 :- http://www.ebay.co.uk/itm/2-TEC1-12709-Thermoelectric-Cooler-Peltier-136-8W-12V-/250880983469?pt=Computing_ComputerComponents_Fans_Heatsinks_SR&hash=item3a69ac01ad

Maybe the two in series will give good cooling at 12v (6v each). These things certainly don't seem to work too well at their rated voltage. It seems that the efficiency reduces as you push them harder.

I was planning to run off an old PC PSU but I may have enough spare current to run off my mount supply - Maplin 13.8v linear regulated PSU.

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mindburner

mindburner

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hey Gina,thanks for the reply. Yes the aluminum around the peltier is not even getting that cold. I havn't even tried doing a temperature measurement yet. That pair you listed from Ebay look pretty good. The single 100w one should hopefully do the trick and I will post up how I get on with it. I recon it will pull about 7 amps, which is more than my 5a mount PSU, so may run a seperate PSU for the cooler.

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Gina

Gina

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I'll be very interested in how you get on :) I have ordered the pair of TECs and will post when I have something to post :hello2:

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Gina

Gina

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The forecast for the next 5 days looks pretty grim :) I'm just hoping for some fine weather so that I can get my obsy roof repaired - got help arranged for this afternoon to lift the heaviest part up onto the top :hello2:

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