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Old 29-07-2009, 05:51 PM
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Easy 40D cooling to -30C

Michael Samerski sent me this http://www.youtube.com/watch?v=6sP45uBj4-k

Its insane (cooling a PC with mineral oil), have a look.

Just think about it, a 40D in a plastic bag, a good one, with 2 tubes out of it. One for oil in and the other out going to a tank (or just past a peltier) that cools the oil to -30deg C (oil freezes well below zero). I bet the shutter will still work.

Do you think the oil between the sensor and the back of a FR would cause distortion? mmmm, some APOs use oil, cant be that bad.

Im tempted to sacrifice my 40D in the name of science, anyone think of a reason it wont work?.
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Old 29-07-2009, 06:00 PM
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The reason would be -30C.. and consequently the ice (in camera, not in space :-) )
A bit too expensive experiment.. for not too much to gain (if you do not count "been there.. done that" )
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Old 29-07-2009, 06:04 PM
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Bojan

Ice?, how so?, its swimming in oil.
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Old 29-07-2009, 06:12 PM
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Ice will be anywhere around.
You can not cool CMOS chip only and prevent the ice forming, say on nearby shutter (and shutter is very sensitive contraption.. I had a problem with it recently, something happened to my 400D when shutter worked but not quite.. enough to invoke "error99" message on the screen), without throughout re-design of the camera.

EDIT
Now, if you immerse the whole thing in oil..
The electronics may or may not work at -30C...
And, oil must be transparent enough...
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Old 29-07-2009, 06:16 PM
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Sorry, I didnt explain well. I mean the whole 40D is immersed in mineral oil, just like the PC in the utube video, no modification at all to the 40D (other than the standard filter).
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Old 29-07-2009, 06:20 PM
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I think the much better approach is cool air (in fridge).
Which is the same principle (only, instead of fluid, you have cool gas inside your camera.
At least, it was proven to work.
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Old 29-07-2009, 06:23 PM
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Quote:
Originally Posted by Bassnut View Post
Sorry, I didnt explain well. I mean the whole 40D is immersed in mineral oil, just like the PC in the utube video, no modification at all to the 40D (other than the standard filter).
Yes, I see... Actually should have seen the video first

But the argument stays:
- Shutter would not work in oil ("error99" would surely come up)
- Flip mirror would not work in oil (maybe this is also monitored by camera firmware)

And, if it does not work.. there is no (low cost) way to clean the camera and have it operational again..

EDIT:
You would have to have the window for light... and as I said in previous post, the oil must be very transparent.
If you do not want any other mod, you will have 44mm of oil between window and sensor.. a lot of (unknown ) filtering..
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Old 29-07-2009, 06:28 PM
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The electrolitic capacitors both SMD & radial will stop working also I fear the zener diodes and some regulators may go way under voltage swing.
The thermal cycling will quickly cause breaks in the tracks of the circuit board.
If that computers oil bath was cooled to zero or lower it would stop working and probably permanently. The electrolitics will pop there seals due to the electrolyte expanding.
I don't want to see you waste a good camera.
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Old 29-07-2009, 06:45 PM
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And, yes, mineral oil.. it is not entirely non-corrosive for IC's and solder joints.
The silicon oil (and silicon grease and rubber), for example is not recommended to be anywhere near solder joints. It has a tendency to go between metal and metal.. and remain trapped there. Then the thermal stresses causes it to expand and very soon this results in miniature explosions, and disconnection of soldered parts.
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Old 29-07-2009, 06:52 PM
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Bojan, yes, I guess it could slow the flip mirror down and cause an error. I thought about cleaning it all, perhaps with immersion in contact cleaner, but then that would also wash out all lubricants in the shutter and flip mirror. The oil looked very transparent, but the thermals in moving oil might cause distortion.

David. OK, yes, the manual states operation to 0 c, so maybe -10 might be possible.

OK, gents, its starting to look like a bad idea ;-)
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Old 29-07-2009, 07:12 PM
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So it seems we managed to save one 40D life :-)
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Old 30-07-2009, 05:04 PM
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I've immersed a computer in chilled mineral oil for cooling purposes... It does work, although I dont think it would be a great idea with a DSLR.. too many moving parts that may or may not like the extra resistance imparted on them by the dynamics and fluid motion of the oil.. I dont know how the shutter would respond when it tries to flip open, and there is the extra pressure of moving the oil around... More hassle than it would be worth I think...

Berts fridge is by far a safer option...
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Old 30-07-2009, 05:12 PM
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Or you could move to Verkhoyansk in Siberia....it drops to 90F below there
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Old 30-07-2009, 05:56 PM
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Alex. I thought about the inertia of the oil resistance, the shutter operates in a plane of minimum resistance, but the mirror might be a problem, depends on the timeout allowed by the firmware for movement before a fault occurs.

David. I checked the operating temps of Electrolytics and micros etc, and they are rated to at least -40c.

In the end, as Bojan says, perhaps you lot have saved my 40Ds life .

Still, im not totally convinced its impossible, but given the hassle, not worth the bother, but I must admit, if it did work, it would be well worth the "been there done that" grin factor.

The grin factor is not to underestimated gents, some of my most satisfying daft projects were due simply to the grin factor .
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Old 30-07-2009, 06:03 PM
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Not a good idea for so many reasons...

In the video he said you can see the currents of hot and cold oil - imagine that in your imaging path.

In the computer the only moving parts were fans. Doesn't matter if they move a little more sluggish as long as they're still circulating the oil. In a camera the timing of the moving parts is absolutely essential. To everything.

Even if there were no currents in the oil, that's a lot of liquid, no matter how clear or good quality it appears to be to the naked eye, that will degrade your image. It's bad enough when you add more optical quality glass or filters in the imaging train.

You won't be able to use that camera for "normal" photography ever again.

It's not portable. Oil everywhere.

It'll become heavier - balancing might get thrown out of whack with a bag full of moving oil. Even if it was a container or something.

Sloshing around as you slew or guiding.

The list goes on. All that risk for what? A cooler chip? So what?

You'll just be trashing your beautiful 40D. I'll cry.
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Old 30-07-2009, 06:12 PM
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Perhaps use the mineral oil cooler to cool a copper cold finger placed behind the sensor.

The other problem with cooling DSLRs is frost and condensation. They aren't sealed chambers like CCD cameras are.

Of course if its immersed in oil that wouldn't be a problem.

Not sure what type of oil is used between refractor lenses.
I should ask as I have often wondered.

Greg.
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Old 30-07-2009, 07:44 PM
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Oil immersion as others have said would be a disaster for any DSLR.

The sensor in my Canon 5DH inside the fridge is 17C above the fridge temperature when exposing continuously. As long as the camera is turned on before cooling the fridge and dummy exposures are taken when the fridge gets near its set temperature there is no condensation as the sensor is the hottest thing in the fridge. I keep the lens at 20C with thermostatically controlled Kendrick dew heaters. Focus does not then change with ambient temperature.
In winter I typically run the fridge peltiers at -10.0C and the fridge with the cameras heat load is at -4.8C. The real advantage of the fridge is that the temperature is constant to + or - 0.1C. This makes dark correction very accurate. The thermal noise is lowered but not totally absent. Using air to cool the camera (there is a fan inside the fridge) means that temperature changes and gradients are never likely to damage the camera. It takes forty minutes to reach equilibrium after first turning on the fridge.
I also always leave the camera on until the fridge reaches ambient after switching it off.
Any water vapour present inside the fridge condenses and freezes on the Peltier heat exchangers.

Cooling the sensor directly would make it the coldest object and then extreme measures need to be taken to keep the sensor and shutter dry.

It would be interesting though to try oil immersion with a much cheaper camera. What is a battered 300D worth now? I am sure it would end up a one shot camera.

Bert
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