Peltier cooling of 1100D sensor chip

[Gina]

Although I'm not immediately doing this mod having only just completed the filter removal, I thought I'd start this thread as somewhere to set down my ideas and maybe encourage comments and suggestions before actually starting.

I now have this link to a cooler "HyperMod" :- Hyper-Modification of Canon 450D (XSi) Cameras

I am not sure how many of the unwanted camera parts I shall remove yet. Having destroyed the ribbon cable that feeds the display I am thinking of removing the LCD screen and putting the Peltier TEC stuff in the hole rather than at the side of the camera. Removing unwanted parts would reduce the weight, of course, and any weight reduction will help compensate for the added weight of the cooler.

I'm also aware of the problem of condensation on the other camera parts. I think a new case would help here. I don't need the bayonet lens mount as I shall be using the camera with my filter wheel once I get it made. In any case a T thread would be better rather than having adapter rings.

[JCJC]

Gina, this is also an outstanding page, CoolCam

ps, had fingers crossed re your dslr filter removal over the last couple of days.

JCJC's Dad

[Gina]

Gina, this is also an outstanding page, CoolCam

ps, had fingers crossed re your dslr filter removal over the last couple of days.

JCJC's Dad

Thank you for that - very interesting Interesting idea to use a hot finger as well as a cold finger. Also a good idea to use spare heat to warm the filter wheel and prevent condensation.

I think he has gone rather OTT on the cooler. I was thinking of using a 10-20W Peltier TEC - we only need to cool the sensor, not the whole camera. I think with a 136W device running at 50W he is heating the air more than necessary. I don't like too much hot air round a scope! Causes the shimmers.

Plenty of food for thought there anyway

[Gina]

A selection of Peltier TECs.

DC 1.9V 0.81W Thermoelectric Cooler Cooler Cooling Peltier TES1-01701 :- eBay - The UK's Online Marketplace

TEC1-04905 DC 5V 19.4W TEC Thermoelectric Cooler Peltier Plate Cooling :- eBay - The UK's Online Marketplace

TEC1-12706 Thermoelectric Cooler Peltier 12V 51.4W :- eBay - The UK's Online Marketplace

[JCJC]

Something like this may provide all the parts, peltier (size?) heatsink, fans, all ready to bolt together.

12V BOAT FRIDGE 12 VOLT CAMPER FRIDGE 240V FRIDGE 240 VOLT FRIDGE CAMPERVAN | eBay

Here is a link to Gary's DSLR mod group, DSLRmodifications : DSLR Modifications

you may know it Gina but others may find it interesting.

JCJC's Dad

[Gina]

Something like this may provide all the parts, peltier (size?) heatsink, fans, all ready to bolt together.

12V BOAT FRIDGE 12 VOLT CAMPER FRIDGE 240V FRIDGE 240 VOLT FRIDGE CAMPERVAN | eBay

I think that's the cheapest I've seen them However, I have a suitable Peltier device (20W 12v) and a fair selection of heantsinks/coolers from old computers.

Here is a link to Gary's DSLR mod group, DSLRmodifications : DSLR Modifications

you may know it Gina but others may find it interesting.

JCJC's Dad

Yes, I belong to that group and will be posting my mods and ideas there.

[Gina]

A selection of coolers - heat sinks and fans. The largest is 80mm then a 50mm and a 60mm heat sink. I should have a 60mm fan somewhere. I reckon the 50mm one would be enough for cooling the sensor chip - I wouldn't have thought the sensor chip would generate much heat. (I know the Peltier itself produces heat.)

[Gina]

Source of copper sheet for cold finger here :- 200x100mmx18swg(1.219mm) C101 Copper Sheet | eBay

[Gina]

I have taken my camera apart again to check on cold finger cooling and have found significant differences between my 1100D and the 450D that others have modified for cold finger cooling. There are a couple of problems which I've detailed with photos below.

This is the 450D (courtesy of Gary Honis.)

And this part of the Hyper-Mod by Anat Ruangrassamee showing an un-needed circuit board removed to access the gap behind the sensor from the side (where the cold finger goes).

Now here are photos of my 1100D main board which continues round the RHS of the sensor unit and pointing out the problems with access for the cold finger. This is making me wonder about using the cold finger cooling method or whether to go for the easier option of blowing cold air into the back of the sensor unit. It may be possible to remove or modify the shield and bend the cold finger towards the back of the camera. More investigation required...

[Gina]

With this much strip down, I can confirm that the camera works fine with the blue ribbon cable (to the back) disconnected as well. So the whole back unit is superfluous for AP and control via the USB connection.

I did a bit more checking for the cold finger cooling mod. The shield comes off easily by removing 4 screws, though two of them are under the main PCB. But that would need removing anyway to get at the side of the sensor assembly to enable the cold finger to be inserted between sensor and circuit board. I now think the cold finger mod is on.

[Gina]

This is how I envisage the cooler. Cold finger (blue) from back of sensor to back of Peltier TEC and hot finger (red) from TEC to shield and sensor frame and hence to camera frame to ward off condensation. The cold finger is insulated both electrically and thermally from the circuit board by a sheet of plastic. Excess heat is removed from the hot side by a heat sink and fan (fan not shown).

[Gina]

Dismantled down to the sensor module again and investigated fitting a cold finger to the sensor back. There is another problem - the clips that hold the sensor. The screws project above the sensor back and also there is a riveted in post that well and truly blocks the way in for the cold finger. The only solution would be to use a lot of force to remove the clips - undoing the screws still leaves them firmly attached to the frame. The other end is no better. I cannot see any way round this that wouldn't endanger the sensor itself.

[Gina]

This is a disappointment I'm not entirely giving up yet though!

I think I also might have a problem with the power. I discovered that the battery cover has a peg which closes a switch so there is no power with the battery flap firmly closed. I also discovered another difference my 1100D and the 450D. The Hyper-Mod shows the upper RH connector (looking at the PCB) as not needed being only used by the SD card. In my 1100D some lines go to the battery assembly PCB and go to the battery flap switch. I've been having trouble with this connector coming loose. Hoping I can fix it.

[Gina]

I've ordered a used 1100D body for just over £230 from Amazon which seems a reasonable deal. I've looked elsewhere but found nothing. I'm thinking of using this while I fault-find on my present one. I'm also thinking of using it for widefield using my old Pentax film camera lenses. I plan to make up a decent bracket to attach it to my main scope. This will detailed in another thread.

Meanwhile, I can go on investigating the cold finger mod on my present 1100D body.

[Ransu]

This may be a silly question, but have you tested how your 1100D handles longer subs without additional cooling? I have used my 600D last autmn, +10C temps and wintertime -20C temps and i dont notice any differense. So i think cooling these new models (1100 and 600) is maybe thing you dont need to do. 1000D shows clearly ampglow in corner, but with 600D i don't see almost any.

Of course it's ok if you want to mod your new toys, but benefit of modding may be small:)

[Gina]

This may be a silly question, but have you tested how your 1100D handles longer subs without additional cooling? I have used my 600D last autmn, +10C temps and wintertime -20C temps and i dont notice any differense. So i think cooling these new models (1100 and 600) is maybe thing you dont need to do. 1000D shows clearly ampglow in corner, but with 600D i don't see almost any.

Of course it's ok if you want to mod your new toys, but benefit of modding may be small:)

Thank you - no it's not a silly question Actually, I think it's a very good point and your results bear that out. I shall do more testing without the cooling. Maybe put the camera in a box with a heater and thermometer and see how much the noise increases with temperature.

When I had a session of a couple of hours with it a few days ago I did notice the temperature rise (APT shows the sensor temperature) but I didn't do a direct test for noise levels.

Although I like messing about with things, if the noise reduction with cooling would be small I probably won't bother. I've got plenty of other things to do

[Gina]

Got my 2nd 1100D body today - described as "used" but it's so clean it looks like new. It's complete with all the bits most of which are packaged like new. I do not intend to do any mods to that yet but have a number of tests I want to do on the unmodified camera.

I shall be continuing the fault-finding on my first 1100D to see if I can get it working again. I won't be going any further with the cold finger mod until I have completed tests on noise levels at various temperatures on the unmodified camera.

[Gina]

At this point I stopped looking at the cold finger mod and concentrated on trying to find why the camera has stopped working. I have started a new thread for this.

I shall be doing tests on the no.2 body to see how much improvement might be obtained by cooling. I might just go for whole camera cooling if cooling is really beneficial. Much depends on whether I can get my no.1 body working again.

[Gina]

I'm now running long dark subs using APT. I've worked up to 20 minutes @ ISO 3200 with T=37C now after a couple of hours testing. The noise is starting to show now.

Now that I know at what exposure the noise starts to show I can do a temperature run with that setting.

I have all the components to make a cooler for the whole camera. A large enough diecast aluminium box, approx 20W Peltier TEC, 80mm square finned heatsink and fan for the hot side and a 50mm square finned heatsink and fan for the cold side (to circulate cold air inside the box.

[Gina]

Having virtually given up on the cold finger direct to the image sensor approach in favour of whole camera cooling I think I should start a new thread with the right title

[Gina]

After a lot of thinking and experimenting with whole camera cooling, I beginning to reconsider the cold finger method. Yes, it's back on the agenda

I've been thinking a lot about how I want to use cameras and scopes. I've come to the conclusion that I don't need two DSLRs as long as I can easily move a DSLR from main scope to camera mount for widefield AP. This means I would want to mount the camera both by its lens mount and by it's tripod bush, and be able to attach lenses to the camera. This also prompts a bit of a re-think about attaching camera to my home made filter wheel.

If I go for the single camera option I don't need to worry about getting my first 1100D body working again and can (very carefully) dismantle my no.2 body as far as the filter removal and swap sensor assemblies, having done the various mods on the no.1 sensor assembly.

[Gina]

I've dismantled my first 1100D body right down to the sensor itself on its PCB. It was easier than I thought - the sensor was stuck to the filter frame with double sided adhesive tape which was quite strong. Having parted that, the sensor came free complete with it's mounting lugs. Unlike other models, there are no copper clips. Here are some photos.

Sensor module looking at image side (front) plus the metal frame.

Sensor & PCB sitting in/on its frame.

Sensor and frame sitting in camera plus main PCB showing gap round sensor PCB and where the ribbon cable goes that connects the sensor PCB to the main board.

Showing where the cold finger might go to the back of the sensor - in blue. This is the only suitable gap. The other side is blocked by the connecting ribbon cable as shown in the photo above. Also, the gap that side has a "dog leg" in it.

This is an edgewise view of the sensor & PCB showing the gap where the cold finger might go. This turns out to be somewhat smaller than on the 450D which was modified with cold finger cooling in the HyperMod articles. The side of the PCB nearest the sensor is completely clear of protuberances except for the pins of the chip (at the left hand side looking at back of camera). These pins reduce the gap still further making it less than the thinnest copper sheet I presently have, which is 22swg. The HyperMods on the 450D use 18swg.

[pete_l]

After a lot of thinking and experimenting with whole camera cooling, I beginning to reconsider the cold finger method. Yes, it's back on the agenda

This isn't something I'd be keen to try myself - far too delicate.

One thing that does spring to mind though. If you place the cold finger (presumably this is what cools the sensor) down one side isn't there a risk that you'd get a temperature gradient across the sensor. So one side of your images would have nice clean, noise-free pixels and the other (hotter) side would be as you have now?

[Gina]

So! We have a problem (Houston)! The gap behind the sensor chip would need to accommodate not only the copper cold finger but some insulation so that it doesn't short out the chip pins plus a few thou for some thermal grease. I think the gap looks like about 0.7mm.

Looking at copper sheet on eBay gives these results :-

Copper Sheet 100mm x 100mm x 0.5mm C106 | eBay

New Copper Sheet 100mm x 100mm x 0.3mm C101 | eBay

I just wonder if much thinner copper sheet (than the 1.2mm = 18swg used in the HyperMods) would still be effective or whether there would be a temperature gradient across the chip.

[Gina]

This isn't something I'd be keen to try myself - far too delicate.

One thing that does spring to mind though. If you place the cold finger (presumably this is what cools the sensor) down one side isn't there a risk that you'd get a temperature gradient across the sensor. So one side of your images would have nice clean, noise-free pixels and the other (hotter) side would be as you have now?

The idea is that the cold finger covers the whole of the back of the sensor chip. So, as long as the copper is thick enough the temperature should be similar over the whole area.