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Old 17-09-2015, 07:26 PM
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ZeroID (Brent)
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DSLR Cooling ....again !

I refuse to be beaten. As anyone who followed the earlier thread on cooling a DSLR noticed, the problem is to get the effect where you need it, at the sensor. The Cold Finger seems to be the only workable solution so I've attacked the problem again from my DIY angle.
The KM 7D is IR modded and expendable. When I did the mod I decided to leave out the internal stainless steel frame that wraps around the back of the camera, couldn't be bothered with it actually.

Using some copper slabs from a couple of big server CPU heatsinks and the stainless frame after some hacking I may have a workable mod.
Progress pictures should tell the story. I milled most of the other metal off the heat sinks and cut a shoulder round the one that will sit behind the sensor. Trying to find some silicon pad material as a non conducting transfer medium to the back of the sensor. I'll join the two copper slabs with a brass screw and some heat compound between or maybe solder them.
The final pic with a radiator on is just a dummy up, may or may not be used but shows the idea. I'll use some standoffs to support the rear screen out a few millimetres to accommodate the finger entry.
The piece of Alum in pics 2 & 3 is just a temp support as is the tube in 4
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  #2  
Old 17-09-2015, 08:54 PM
glend (Glen)
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Good luck Zero I will be following this with interest. One thing I have found is that copper cold fingers do add weight to the final assembly and the less you can use the better the balance on the focuser/scope. Is it possible to shave that copper slab down abit? The weight of the fan and heatsink will also put force loads on the cold finger within the camera and the attachment to the camera is important. A silver based thermal paste is adequate for transfering cold to the sensor back, I used Artic Silver.
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Old 18-09-2015, 04:44 AM
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ZeroID (Brent)
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Hi Glen,
Yeah, I could mill a fair bit off if required but I was thinking to use the thermal mass to stabilize the system. The stainless back plate will be secure enough and the radiator assembly is surprisingly light for it's bulk. My scope setup is quite robust and light for the mount. I think the earlier setups with plastic boxes and associated hardware would be heavier than this and I have some other options for radiators.
I'll have a hunt round for some Artic Silver, I assume it is non-conducting ?

EDIT:
Just had another thought. If I mill most of that copper 'island' on the larger slab off I may be able to mount the TEC and radiator under the camera out of the way and reduce the balance\weight issue. Must investigate further.
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Old 18-09-2015, 06:48 PM
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Camelopardalis (Dunk)
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The question on everyone's lips is... will you be offering a conversion service?
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Old 19-09-2015, 12:20 PM
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rcheshire (Rowland)
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Nice to have the tools and skills Brent - looks like a very nice job

I'm not sure you need worry about thermal stability too much. Peltiers seem to do OK by feeding just the right amount of power for the temperature, analog or digital control. The mass of a 1.2mm coldfinger, as used in the Canon's you've no doubt seen on the forum, is adequate to hold temperature for several seconds once power is removed. I find my system very responsive and accurate +/-0.3C, most of which is the digital switching effect on analog sensor readouts.
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Old 21-09-2015, 05:04 AM
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ZeroID (Brent)
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Quote:
Originally Posted by Camelopardalis View Post
The question on everyone's lips is... will you be offering a conversion service?
I doubt it, the Konica Minolta 7D internals are different from the Canons. I chose to use it because it is expendable and the stainless back and internal layout presented an option. If I can get it working though I will investigate one of the Canon models if I can find another cheap buy somewhere. The 450D I bought previously was a bargain at $70 due to a fault ( lens focus connection issues) which didn't bother me obviously but most have been going at the well over $300 mark.
10D, 20D, 350D etc seem a lot cheaper but still significant $$ and may not be similar to useful models with Live View which was the appeal of the 450D plus 12.2 megapixel of course.

If I can find another 450D or better still 1100D\1200D then I'll open up the 450D and take a look. I have quite a bit of copper accumulated from scrapped PC's\Servers at work. It's a slow process though, there is quite a bit of work involved. I've milled some of the copper island off to reduce weight and povide a flat TEC mount option but it's a small mill so small bites.

If anyone's got a suitable model they are willing to donate or provide at reasonable cost .. ....

I'll take a look at the 450D IR mod instructions again to get a better idea of feasibilty. Basically at present I don't want to lose my 450D as it's too useful as it is.
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Old 21-09-2015, 07:25 AM
glend (Glen)
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I keep a watch on ebay for bargain Canon 450Ds and that's how I found my current spare for less than $200. There is a local (au) one sitting there now for $180, which if the ad can be believed was only ever a backup camera so may have little shutter count:

http://www.ebay.com.au/itm/Canon-EOS...item4af0e758f7

There is a local (au) 1100D up in ebay au as well (bids required) from $150 that would be worth watching.

http://www.ebay.com.au/itm/Canon-EOS...item3ab21fc0e5

Plenty of them around the world (US and UK especially at reasonable prices if you don't mind the shipping, but local buys are usually more cost effective. Even supposed non-working cameras can be a great find, things like the shutter module are easily changed if your stripping it down to mod it anyway. You can buy new OEM shutter modules for about $50, and that's the only real wear and tear item you'd be worried about.
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Old 21-09-2015, 11:43 AM
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Camelopardalis (Dunk)
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Yeah I'm keeping my eyes open for one locally, even a broken one to practice on as I'm reluctant to break open my camera that works so well (given sufficiently cool weather) without knowing what I'm doing
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Old 25-09-2015, 07:52 PM
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Dunk, I've opened my 450D recently. It was my first time molding a dslr. Doing the uv/ir mod to make it full spectrum was both simple and quick and for the fact that I only use this camera for Astrophotography makes it now an invaluable tool.

I am hoping to pickup a second 450D to attempt a cold finger on. Last night outside temps were chilly chilly and after an hour or two of imaging the sensor was still a toasty 25c

I used icnr and results were clean enough but far from perfect.

I got some incredibly useful info from Glen last week as I was originally planning to do a cold box. I think I may use my knowledge of computer water cooling (as well as my extensive list of CPU cooling spares) to get the best out of it. I don't know how to seal mine up though as I'm using it on a camera lens.

Dunno if a nichrome wire heater on the glass is the go. Dunno dunno dunno.

Lots to think about but it's great having so many people on here who have done it.
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Old 27-09-2015, 05:12 PM
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ZeroID (Brent)
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Ok, so here's how you solder two big pieces of copper together if you haven't got a decent gas torch.

Photo is not too good, my little Fuji is not keen on low lit close ups. But I've milled most of the 'island' off just leaving a low shoulder to butt the sensor plate against. Get onto the Wok burner and bring it up to heat then just wick the solder into the joint.

I had been intending to get subzero temps with this but reading the other thread on this subject staying above 0 in the 5-7* range is easier to manage with dew\ice issues and is still quite effective with noise reduction.. This means I can reduce my external heat sink size and weight requirements and run the TEC down in 5 volts region.
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