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1100D cold finger sensor cooling with TEC and water cooling


Gina

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I'm in good company then! :)

I've been having a well overdue clear up and the Peltier has turned up - where??? - just where I'd looked at least twice before!! :headbang:

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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.
Errm , hope you don't mind me butting in :). I took a look at the photos you put up about your cooled DSLR and the later comment that the ali box isn't getting that cold.

In the photos I couldn't see any insulation around the box. Did you remove it "for photgraphic purposes"? I'd expect that when the box+Peltier is running there wouldn't be any of it's surface exposed to feel it's temperature.

Normally you'd reckon that a Peltier would get up to about 50% efficient. So one that consumes 50Watts of electrical power would give you 25-ish Watts of cooling, which should be enough to make some difference to a DSLR as that (guess) uses maybe 10Watts from it's battery [ sidenote: the batteries don't like the cold, they lose a lot of their capacity ]. Now, that does assume that the "hot" side of the Peltier is configured to efficiently remove all that heat: the 50W from the power source *and* the 25W from the cold side.

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I've now got the 5v 20W Peltier next to the cold finger and the 12v 50W Peltier on top next to the water block. Running from PC PSU at the rated voltages. Now have a remote thermometer attached to the cold finger where it goes into the camera. The system has just about settled now I think and the cold finger is at -12.5C and the EXIF T is -4C. Quite a temperature difference!! So clearly if I can get the 5v Peltier nearer the sensor it should be better, as I thought. Also, this combination of Peltier TECs should provide quite adequate cooling if I can get the cold finger differential temperature down a good bit.

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That's good news Gina. Have you considered a 2 sided finger, cooled from 2 sides, a TEC on each side of the camera?
Thank you :) Unfortunately it isn't possible to bring the cold finger out the other side of the sensor as there is a ribbon cable in the way - the one that connects the imaging board to the main board. I would have liked to have been able to feed cold in from both sides as it were.
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I've now got the 5v 20W Peltier next to the cold finger and the 12v 50W Peltier on top next to the water block. Running from PC PSU at the rated voltages. Now have a remote thermometer attached to the cold finger where it goes into the camera. The system has just about settled now I think and the cold finger is at -12.5C and the EXIF T is -4C. Quite a temperature difference!! So clearly if I can get the 5v Peltier nearer the sensor it should be better, as I thought. Also, this combination of Peltier TECs should provide quite adequate cooling if I can get the cold finger differential temperature down a good bit.

Gina, do you happen to have a picture or a diagram of that test setup? I've tinkered with my cooling many hours this weekend again but I fail to get the far side of the cold finger to below zero.

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Gina, do you happen to have a picture or a diagram of that test setup? I've tinkered with my cooling many hours this weekend again but I fail to get the far side of the cold finger to below zero.
Here's a diagram. Cold finger next to Peltier at -19C and EXIF T = -9C ATM.

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-9C !!! that sounds like your there, cascaded seems to be working. I was thinking you could encase the camera in a lightweight foam box with some desiccant, that would also stop the devices from cooling the room air and ending up covered in ice.

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Here's a diagram. Cold finger next to Peltier at -19C and EXIF T = -9C ATM.

Ah, I see.. thanks ...

It sounded like you now had 2 peltiers in different places... But then, it was quite late when I read your post .. ;-)

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-9C !!! that sounds like your there, cascaded seems to be working. I was thinking you could encase the camera in a lightweight foam box with some desiccant, that would also stop the devices from cooling the room air and ending up covered in ice.
Pretty much there yes. I was intending to encase the external cold bits in foam once I'd finalised on the arrangement.
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Ah, I see.. thanks ...

It sounded like you now had 2 peltiers in different places... But then, it was quite late when I read your post .. ;-)

Well, I can understand the confusion because one option I posted was/is to put the smaller Peltier inside the camera as close to the sensor as possible and the larger one outside with thicker copper strip between the two. That's what I shall be looking into next. I would like to reduce the cold area as much as possible, as well as reduce the thermal resistance. Moving the inside to outside thermal link to the intermediate temperature will reduce ice formation and heat gain from that.
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you could torch the finger end of the sheet and while hot hammer it out more thinner, thing is the plate. alot of wanted cooling is being wasted.

[]== this sort of shape would be more ideal , the square holding the tec devices, and the long finger just the right size of the sensor back plate. this way more cooling is directed down the thinner finger than that of a plate.

there is going to be a wall you hit where cooling and transfer stops -19/-9 is good for a homegrown cooling system, without R&D.

real testing will come in the later summer months as the temp stars soaring. if not a nice toasty warm room (in the 80's) will give a rough idea of the minimum temps you could possibly reach

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you could torch the finger end of the sheet and while hot hammer it out more thinner, thing is the plate. alot of wanted cooling is being wasted.
Possibly.
[]== this sort of shape would be more ideal , the square holding the tec devices, and the long finger just the right size of the sensor back plate. this way more cooling is directed down the thinner finger than that of a plate.
This is pretty much the shape I have already. Unfortunately the narrow part is rather long.
there is going to be a wall you hit where cooling and transfer stops -19/-9 is good for a homegrown cooling system, without R&D.
Oh yes, I'm aware of that. I'm quite pleased with the cooling but think there's room for improvement using these two Peltiers.
real testing will come in the later summer months as the temp stars soaring. if not a nice toasty warm room (in the 80's) will give a rough idea of the minimum temps you could possibly reach
Oh absolutely. I would like to have some cooling in reserve just in case we get a hot spell.
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Made a cold finger to minimise distance from 5v Peltier to sensor by folding the finger to lay on top of the imaging board. I've also filled the gap with thermal paste (electrically non-conducting).

  1. Camera with imaging assembly in position
  2. Camera with main board as well
  3. Diagram of camera cooling

Coldfinger-10.jpg

Coldfinger-11.jpg

Cooler-TECWB-4.png

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The present system with stacked Peltier TECs just outside the camera case is performing adequately with the present ambient temperature of around 6C giving -10C to -11C EXIF T. I can probably improve the cooling by lagging the TECs and cold finger but not sure this would be enough for a heat wave in the summer if we ever get one.

Meanwhile, I shall be looking into the newest idea of putting the smaller Peltier inside the camera and the larger one outside though the small one may be sufficient on its own with the better thermal connection to the sensor with just the water block on the outside.

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Been looking at the camera, USB connection and arrangement of cooling parts. I have both straight and right-angle USB connector cables. Attached are diagrams of four possibilities :-

  1. USB connector going through a hole in the warm finger (as previously posted).
  2. The USB cable replaced by right-angle one avoiding the need for a hole in the warm finger.
  3. Warm finger without either hole or bend and the Peltier and water block facing forwards instead of sideways.
  4. Warm finger without either hole or bend and the Peltier and water block facing backwards instead of sideways.

Any thoughts on these options would be appreciated :)

I'm tending to favour no.3 or no.4 avoiding both the hole in the warm finger and the bend. No.4 also reduces the thermal path. Only downside is that the centre of gravity is pushed slightly further from the focuser increasing the loading on it and the water tubes are slightly longer. OTOH the weight of Peltier and water block is only a fraction of the weight of the camera and may not be significant.

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