Peltier cooling of 1100D sensor chip

[ponytale]

Gina would it be possible to use a vacuum cleaner bag the 5 layer paper type with the lens poking through the inlet hole and the fan sucking through the camera spaces and exhausting outside of your cooler box , I am sure air will flow better being drawn in than pushed out eg: car radiators . these bags are supposed to filter down to micron levels to remove allergens and pollen , also some anti static spray to repel particulates ? would be useful . regards Tony

[Gina]

a very interesting project you got there Gina as all of your projects. A 2p of my opinion. By watching the fan you placed at the back of the camera you might consider about dampening any possible vibrations from the fan that will cause trails at your image. I mention it because i had to install an on/off switch at my first ccd camera (an atik 16 ic) since i had vibrations, i had no cooling problems with that camera since the whole casing of the camera acted as a huge heat sink

Thank you Yes, vibrations from the fan are a concern. I'm hoping I might be able to get away without a fan. Otherwise I may be able to suspend it on rubber bands or polyether foam.

[Gina]

OK - Have IR thermometer - nice instrument

Have disassembled camera no.2 as far as getting to the main PCB and removing the back part and now running APT taking a series of subs and waiting for things to heat up a bit. So far so good - camera working fine from USB Had no problem getting the case screws undone this time

[Auntystatic]

Stick the ribbon cables from the back into your no1 camera and see if its just wanting the date and time set.

[Gina]

Image sensor temperature is now running at 32-33C and shown below are the temperatures on the board and other components as measured by the IR thermometer (in red). The camera back is open to the environment and lens down (have a Pentax 35mm film camera lens on). So there is a certain amount of convection and radiation cooling.

The hottest area is the big chip on the right (no surprise there) but the sensor is running a couple of degrees higher than the surrounding components including the PCB it's attached to. Ambient temperature is 24C.

[Gina]

Stick the ribbon cables from the back into your no1 camera and see if its just wanting the date and time set.

Good idea Thanks

[Gina]

Sensor temp now 34C and steady - running continuous 5min subs with 5s pause.

Board temps much the same, chips also, but the sensor board and connector show an increase of a degree C. The screen has gone from 25 to 29C. The latter my be being heated by the chip behind it. Later I think I shall remove the screen to access that chip with the IR thermometer.

[Gina]

Gina would it be possible to use a vacuum cleaner bag the 5 layer paper type with the lens poking through the inlet hole and the fan sucking through the camera spaces and exhausting outside of your cooler box , I am sure air will flow better being drawn in than pushed out eg: car radiators . these bags are supposed to filter down to micron levels to remove allergens and pollen , also some anti static spray to repel particulates ? would be useful . regards Tony

Sorry, missed this post earlier... Thanks for the suggestion, I'll give it some thought

[Gina]

Well I put no.1 back together with the back off no.2, powered up and... nothing Guess I could try removing and replacing the lithium battery - see if it will reset. Getting the display ribbon connected was extremely fiddly.

[Gina]

Dismantled no.1, took the lithium cell out and checked the voltage - 2.8v. Then put it back and put PCB back. Continued tomorrow...

[Gina]

Back onto the cooling topic...

Tomorrow I will remove the screen from the sensor PCB and see how hot the chip behind it gets. But I think the sensor itself must be generating some heat as the sensor board itself gets hot away from that chip.

[Auntystatic]

I was really really hoping that it was just awaiting the date to be input, sorry it didn't work, but it might just be something simples that's causing the fault, and yes those display and buttons cable are blumming fiddly.

[Gina]

I was really really hoping that it was just awaiting the date to be input, sorry it didn't work, but it might just be something simples that's causing the fault, and yes those display and buttons cable are blumming fiddly.

Oh yes, in fact I'm not entirely sure I got the display cable fully into the connector. I put the back back onto it's original body (no.2) and really made sure the ribbons were properly connected. Result - yes working as before. Tomorrow I'll move it to my no.1 camera and see if either a better connection or resetting the memory has made any difference. At least I know testing the non-working camera with a working back has not upset the working back

[obscura]

For interest someone has a 450D modded and peltier cooling on sale Astronomy Buy & Sell for £200. Item 53799 currently first page.

[Gina]

For interest someone has a 450D modded and peltier cooling on sale Astronomy Buy & Sell for £200. Item 53799 currently first page.

Ah yes, that looks a good buy for someone

[Gina]

Stripped no.2 body down as far as removing main PCB and renoved screen from sensor assembly. Put it back together as far as needed for USB control from APT and now running continuous subs of 5mins.

Temperatures (degrees C) as follows :-

• Ambient - 19
  
• Sensor - 33
  
• A - 27
  
• B - 30
  
• C - 30
  
• D - 29
  
• E -26
  
• F - 28
  
• G - 21
  
• H - 23
  

[Gina]

Conclusions from readings above :-

1. The sensor chip is by far the hottest item going by the EXIF data.
   
2. Chip A that was originally behind the screen does not seem to be self heating - I think it is being warmed by the sensor chip immediately below it (camera is lens down).
   
3. Chips B & C are producing heat but they aren't as hot as the sensor.
   

[Gina]

So... It is the sensor that wants cooling mostly. I've now placed the camera upright - sitting on a cold radiator. Ambient temperature has risen to 22 and radiator is the same.

Most temperatures have dropped a degree C due the the improved convection cooling of the vertical main board including the sensor.

[Gina]

Latest results (with previous results in brackets) :-

• Ambient - 24 (19)
  
• Sensor - 33 (33)
  
• A - 30 (27)
  
• B - 33 (30)
  
• C - 34 (30)
  
• D - 32 (29)
  
• E - 29 (26)
  
• F - 30 (28)
  
• G - 24 (21)
  
• H - 28 (23)
  

Oddly, although ambient and other temperatures have gone up, the sensor is still the same.

[Gina]

I'll see what I can work out for direct cooling the sensor chip but I'm thinking of just using thermal paste as mentioned by RAC, but not taking the temperature as far down to avoid freezing.

I did some testing with my 1000d with a peltier on the back of the sensor. The 1000d has a metal shield over the circuit board that holds the sensor, all i did was fill the gap between the shield/circuit board and circuit board/sensor with heatsink past then mount the peltier on the shield. This takes the circuit board down in temp too, i had a thermocouple on the back of the sensor also.

I have some electrically insulating thermal compound which I can use quite liberally without worrying about shorting anything :- Arctic Silver Ceramique 2 (2.7g) Tri-Linear Ceramic Paste Thermal Compound: Amazon.co.uk: Computers & Accessories

[Gina]

Well, I tried to get thermal paste in between the PCB and the sensor but couldn't get it in - gap too narrow. So gone back to Plan A - a cold finger. Used 22swg copper sheet cut to 25mm wide and about 75 mm long. I left the plastic coating on one side to provide electrical insulation. Bent the copper strip twice to produce a U shape and liberally coated one side with thermal paste to contact the sensor. Also pushed paste in round the end of the finger. I plan to put a Peltier TEC on the other side of the U.

Photo to follow.

[Gina]

Photo as promised. I may try just thermally connecting the cold finger to external fins and see if I can get sufficient cooling that way without a TEC. I've been working on the no.1 sensor assembly which has also had the filters removed. So next stage will be to strip down no.2 camera again and swap sensor assemblies.

[mindburner]

very interesting post Gina. I have just ordered a 1100D as a replacement for my nikon which I need for other uses. I hope to mod the 1100D by removing the IR filter and using a Baader Neo IR/UR filter that I already have. I don't need the Canon for anything else just astro. It looks like this camera model has low amp glow and noise, so should be an improvemen t over my current camera.

I read about your issues with ribbon cable so I will be looking out for that one. Although I may go down the cooling route myself and not use the LCD screen anyway.

keep up the great posts

[Gina]

very interesting post Gina. I have just ordered a 1100D as a replacement for my nikon which I need for other uses. I hope to mod the 1100D by removing the IR filter and using a Baader Neo IR/UR filter that I already have. I don't need the Canon for anything else just astro. It looks like this camera model has low amp glow and noise, so should be an improvemen t over my current camera.

Thank you I think you should be very happy with the 1100D - I am

I read about your issues with ribbon cable so I will be looking out for that one. Although I may go down the cooling route myself and not use the LCD screen anyway.

Yes, you have to be very careful - all the way through, in fact. Good luck with it

keep up the great posts

Thanks - I will

[Merlin66]

Mindburner,

if you only remove the colour balance filter, the remaining front filter, the anti-alias/ dust filter provides the UV-IR cut-off. No need for an additonal filter unless you need AF etc.