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diy peltier

ponytale

By ponytale
in DIY Astronomer

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ponytale

ponytale

Posted
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hi all diy'ers,and camera modifiers. i have just disasembled a 12v camping gaz cooler box that was damaged and saved the cooling device (2 finned alloy blocks with a peltier and a small pcb with a socket for 12v dc ,) i know that the box could be used for cooling or warming by putting plug in reverse , it has a small sensor on the cooling element block which i assume is a temp sensor , if it is i wonder if i could put a potentiometer in to make it adjustable? i think the finned blocks could be exchanged for smaller computer cpu blocks or cut down and then the units could be used to cool a ccd camera in a box or with a cold finger to ccd chip , any thoughts on this or has any one used one of these before? it also has a small dc motor which drives a fan to take away excess heat, i will put pics up as soon as i have chance . Ponytale

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nightvision

nightvision

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Great idea recovering the bits, I just bought 2 90 watt Peltier devices (£1.79 each) on Ebay. I am going to use some old PC CPU heatsinks and minature 12v fans. Building a cooler for my 300d, I think the biggest challenge will be preventing condensation and not reducing the battery capacity too much, I plan to include some dessicant for moisture control. Still working on an external power supply solution.

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The Stoat

The Stoat

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I have mine attached to a tripod leg and it doesnt get in the way. I run it from an RCD protected outlet and I've not had an issue with moisture so far, but it's a fair point and I'll keep an eye on it.

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msinclairinork

msinclairinork

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Great idea recovering the bits, I just bought 2 90 watt Peltier devices (£1.79 each) on Ebay. I am going to use some old PC CPU heatsinks and minature 12v fans. Building a cooler for my 300d, I think the biggest challenge will be preventing condensation and not reducing the battery capacity too much, I plan to include some dessicant for moisture control. Still working on an external power supply solution.

I am in the same position as you! :D

I bought those too and have a 300D so will be attempting the same thing.

My thoughts on power was to use a a cheap(ish) bench power supply (ebay ~£30), not very elegant nor compact, but would allow you to controll the tempreture somewhat? Would certainly be usefull in testing first, then find an suitable supply matching current.

Thanks,

Michael

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nightvision

nightvision

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I am in the same position as you!

I bought those too and have a 300D so will be attempting the same thing.

My thoughts on power was to use a a cheap(ish) bench power supply (ebay ~£30), not very elegant nor compact, but would allow you to controll the tempreture somewhat? Would certainly be usefull in testing first, then find an suitable supply matching current.

Thanks,

Michael

I've read on another forum that if the peltier is just left to run it will eventually bottom-out and then begin to warm up, at this point I think the power needs to be lowered. That's why I got the temp sensor. Should be able to map out what it does on the bench and see if I can build a simple circuit to alter the supply current or voltage. It will be manual to start with but once I get a handle on the characteristics it should be possible to automate it.

I think the biggest challenge will be preventing condensation or ice building up around the sensor especially in the summer. I have plenty of Silica I intend to place inside the OTA near the focuser and inside the empty battery. I will install a nichrome heater system to dry out the silica after and or just before a session.

Some mod'rs have stripped the 300D down to its internals and re-housed it; I don't think I'll be going that far, just yet.

BTW I really like your obs and pier (and your dark location), very nice, one day maybe...

Have you upgraded the firmware? Now has mirror lock and programmable shutter delay and 3200.

Tony.

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msinclairinork

msinclairinork

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Hi Tony,

Thanks for the heads up on that, you sound alot more clued up on this malark than me and certainly more elecrical minded!

I would appreciate if you would be willing to post your results and method once you get their?

Yeah I upgraded it a while back, was surprised how easy it was, which was a nice bonus! :D

Yeah the permenant setup soloution will hopfully get finished next month, just going for cheap, small and simple as possible but also having setup time minimised to the fullest.

It's still quite urban where I live, but not that bad and thankfully now that we have moved there are no street lights hitting the scope directly which is always a good thing! :)

Keep me posted with your progress, and I will do the same :)

Cheers,

Michael

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msinclairinork

msinclairinork

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Oh thoughts on moisture; would having an extraction fan in the cooler help things a bit?

Also, I have been told that an old foam camping mattress makes for a good dew shield, so how about lining the inside with some of that? and of course as you say a few sillica packs too.

Michael

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nightvision

nightvision

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Hi Tony,

Thanks for the heads up on that, you sound alot more clued up on this malark than me and certainly more elecrical minded!

I would appreciate if you would be willing to post your results and method once you get their?

Yeah I upgraded it a while back, was surprised how easy it was, which was a nice bonus! :D

Yeah the permenant setup soloution will hopfully get finished next month, just going for cheap, small and simple as possible but also having setup time minimised to the fullest.

It's still quite urban where I live, but not that bad and thankfully now that we have moved there are no street lights hitting the scope directly which is always a good thing! :)

Keep me posted with your progress, and I will do the same :)

Cheers,

Michael

Will do, need more time to do this important stuff but at least I can plan while doing DIY! :(:)

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nightvision

nightvision

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Keeping the air-flow up seems intuitively good but if humidity is high it will just supply more moisture, like leaving the fridge door open.

I have used that sort of dew sheild on my 12" dob opening but I don't think it would make much difference inside the APO tube.

Thought about making sure the inside of the tube is dried out prior to attaching the camera (pre heated Silica) or to use a de-humidifier to feed your fan idea but that would also need filtering to prevent dust ingress.

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nightvision

nightvision

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Yes that's what I am planning to do.

My concern may be unfounded but others have run in to the problem; if the whole camera is cooler than the air inside the OTA then the sensor will be cooler than the air in the OTA especially in the summer. That means it will be where any moisture in the OTA condenses. It makes sense to line the camera box with something insulating.

If I lived in a dry desert I guess it would be less of an issue but the humidty here on the coast is usually high.

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msinclairinork

msinclairinork

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Yes that's what I am planning to do.

My concern may be unfounded but others have run in to the problem; if the whole camera is cooler than the air inside the OTA then the sensor will be cooler than the air in the OTA especially in the summer. That means it will be where any moisture in the OTA condenses. It makes sense to line the camera box with something insulating.

If I lived in a dry desert I guess it would be less of an issue but the humidty here on the coast is usually high.

hmm...I don't think this should be a problem, otherwise no one would buy cooled ccd's?

Michael

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msinclairinork

msinclairinork

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Yes, this is extreme! I won't be doing this either! lol

Intresting point raised about increased amp glow once the chip is cooled.

I suppose the only way to know for sure will be testing. And if moisture is a problem then your idea of puting in heated silica could well be the remedy needed.

p.s your point about the sensor being cooler than the air inside the tube causing moisture build up, does make perfect sense, and where I live being on a small island moisture is high too. But this has really made me confused to why off the shelf cooled ccd camera do not seem to have this problem? :D

Might post that question in the imaging disscusion, see if cooled ccd owners do have this issue from time to time or know the reason why it doesn't happen.

Michael

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Steve 1962

Steve 1962

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I built one of these last year using Gary Honis' article as a guide..and it works a treat in colling the camera to about 20c below ambient.

I would strongly recommend sealing the chamber as best you can, and putting in some silica gel (which can be microwaved or baked in an oven to make sure it's dry before use) - even taking these precautions I still had quite a lot of moisture condensing inside the chamber so I'd test whatever you build before putting several hundred pounds worth of DSLR inside.

The other thing I'd advise is to keep the weight down as much as possible - mine was (is) heavy enough to make the focusser on the WO ZS70 deflect...so after all the work in building the thing I have a choice between lower noise levels or consistent focus. I'm looking for a method supporting it and retaining a degree of adjustment while reducing the load on the focusser.

Hope this helps

Steve

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nightvision

nightvision

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...

p.s your point about the sensor being cooler than the air inside the tube causing moisture build up, does make perfect sense, and where I live being on a small island moisture is high too. But this has really made me confused to why off the shelf cooled ccd camera do not seem to have this problem? :D

.....

Michael

See here; for example read the blurb on the QHY10 and also see the last item on the page, it's a problem but not the biggest we'll likely face!

QHY10 QHY12 QHY9 QHY8 QHY6 QHY6 Pro QHY5 QHY2 Pro Exclusively @ Modern Astronomy

BTW on the amp noise, I think it's just a case of 'get rid of one problem and another becomes an equal issue' even though it's a much smaller issue it seem to be just one more thing for him to tackle, check out his test exposure times, no way I'll ever go that long unless I move to Arizona.

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Steve 1962

Steve 1962

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What material did you use for the housing its self?

Hi Michael

I used 1.25mm Aluminium sheet for the casing and lid.

Here's link to what I built which includes the various heat sinks and fans etc;

http://stargazerslounge.com/equipment-discussion/107494-peltier-cooler-canon-dslr.html

I'll be really interested in hearing how you get on

Cheers

Steve

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