DSLR Cooling to Near Ambient with Fan Cooler

[Gina]

When I've been imaging with my DSLR without cooling the EXIF T temperature reading rises to at least 14 degrees C above ambient. So it occurred to me that I could get a good reduction in noise by cooling the image sensor to near ambient temperature. Noise doubles with each 7C rise in temperature so cooling to a couple of degrees above ambient should give a worthwhile noise reduction. If this proves incorrect I could quite easily add a Peltier TEC between cold finger and cooler.

In any event the idea is to do away the extra box and just use the camera case as it is - except for a modification to the back, removing the LCD screen and feeding the cold finger out through a slot. This is for my wide-field camera - the scope camera is already cooled.

Diagram to follow ...

[Gina]

Here is a diagram showing the camera with cold finger (in blue) inserted behind and in contact with the image sensor. This then comes outside the camera and into thermal contact with a fan cooled CPU cooler. Thermal paste is used on the cold finger as usual. Circuit boards are shown in green and ribbon connector between imaging board and main board in yellow.

[Gina]

Some photos of the cold finger. Just made and then fitted in the camera. Copper sheet is 22swg C101 standard 99.9% Cu. A part of the cold finger was bent up to provide a housing for a digital thermometer which I may use later if I go for set-point temperature control (much easier to do it when making the cold finger than later).

[fwm891]

Looks like your cutting back on thermal paste for this one Gina

[Gina]

I'm running out Francis, so need to conserve it

[Gina]

More photos...

The main board put back in the camera and connected up. The camera was tested at this time and confirmed working. The third photo shows the cooler I plan to use. It's 60mm square with a seemingly very efficient set of fins - we'll see

[Gina]

Been running some tests tonight (after a hiatus with a stray screw, which lodged in the SD card slot and was the devil to remove). Didn't get as far as fitting and running the cooler but ran APT with 60s exposures continuously and the EXIF T reached 28C with ambient of 22C. Normally it would rise to something like 35 to 40 indoors. So I guess the cold finger was removing some heat and radiating/convecting it away from the 40mm square pad the cooler will go on. Also, the back was off, again helping with cooling.

I'm hoping to run proper tests tomorrow when I have more time. I need to construct a couple of brackets to secure the cooler first.

[Gina]

Have now put the back on and running tests. I'm also making up the attachments for the cooler. The EXIF T is now running at 31C having risen from 24C when I started the run. Hopefully there will be readings with the cooler on and the fan running later today.

Here's a photo of the camera with the back on. The green wire earths the coldfinger to the camera metal frame.

[Chris]

It was impressive enough that you did all this hyper modding to your first camera, now your miniturising the whole thing!! Really cool thread Gina, no pun intended:)

[Gina]

Now running 5m subs at ISO3200 and getting 35C EXIF T with 23C ambient. Cold finger feels decidedly tepid, almost warm

One cooler fixing clip made - the other this afternoon I expect.

[Gina]

It was impressive enough that you did all this hyper modding to your first camera, now your miniturising the whole thing!! Really cool thread Gina, no pun intended:)

Thank you Chris

[Gina]

Now have cooler attached to cold finger with thermal paste between and fan running at the full 12v. Still running 5m subs at ISO3200 and EXIF T is now 27C with ambient of 24C. So I'm 3C above ambient and 7C below what it gave with cold finger and no cooler. I estimate I'm getting 11 degrees of cooling compared with a standard camera. This is pretty near what I expected though I was hoping for 2C above ambient but I got that with the relatively huge Zalman heat pipe cooler. 11C lower temperature means about a third of the noise if my maths is right

I think that is just about it. I think it's about as far as I can go without taking measures to reduce the local humidity as much below ambient + 3C will be getting dangerously close to the dew point unless the weather is very dry. Even that amount of cooling may be too much on a damp night

[Gina]

Just gone over and looked at the latest readings...

APT running 5m subs with 2s pause at ISO 3200 is showing EXIF T of 26C. A room thermometer nearby is reading 23.6C. Comparisons against the DS18B20 shows this relatively cheap digital thermometer to be accurate to within half a degree C (the quoted accuracy of the DS18B20).

I've now set up APT for 10m (600s) subs at ISO 3200 to see what the noise is like. With the case on there's no noticeable light getting onto the image sensor.

[Gina]

10m subs at ISO 3200 with APT showing EXIF T of 25C with ambient of 22.9C. The noise is visible. I'll post an image later.

[JamesF]

That sounds pretty good though. When solar imaging I quite often see the EXIF T figure creep up to 35C on my 450D when the ambient temperature isn't much more than 21 or 22C.

James

[Gina]

Yes, that is about the temperature rise I see with my uncooled 1100D - about 14C.

[JamesF]

It did start me wondering what sort of temperatures the camera can get up to if it's used fairly heavily during the day on a holiday to somewhere fairly tropical. I guess you could easily start with an ambient temperature of 35C then.

James

[Gina]

I've had my EXIF T up to 50C in the past when doing solar imaging on a hot day No it wasn't this year! But in "normal" photography you wouldn't be using such long exposures and the sensor heating wouldn't be a problem.

[JamesF]

I shan't worry just yet then

James

[Gina]

Parts List :-

• Copper Sheet - http://www.ebay.co.uk/itm/250383031488?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649
  
• CPU Cooler - http://www.ebay.co.uk/itm/250383031488?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649
  

[fwm891]

Your links are identical Gina (CPU cooler)

[Gina]

Cooler attached to camera.

[Gina]

Your links are identical Gina (CPU cooler)

Are they? - Oh I'll check and repost.

[Gina]

Trying again...

Parts List :-

Copper Sheet - http://www.ebay.co.u...984.m1439.l2649

CPU Cooler - http://www.ebay.co.u...984.m1439.l2649

Seems to be right now...

[Chris]

That looks very neat, compact, and usable, what a result! if modding the 300D goes well I might just have to give this one a go, but maybe on my350D:)