My take on DSLR peltier cooling

[Luis Campos]

Hi all,

This was something I had in mind a long time ago, but seening the thread started by Gina (cheers GINA ) i was encouraged to proceed with the mod, my only concern is taht I know absolutely nothing about electronics, so was like playng in lotery...lol

Nevertheless i decided to take a go on it, trusting my mechanical skills (i'm a bicycle mechanic specialized in shocks /forks) it was very complicated I confess, making measurements, cuts, soldering etc...I allmost went nuts, when I finished and inserted the batery...pushed the on button...closed my eyes for like ten seconds...and when i got the courage to open them up, the camera was working, HURRA!!!!!!

So, I've made some first tests, and you can see in my Flickr page some pics regarding the mod and some dark frames for testing, although I used an aluminium cold finger (it was what i had in hand) still works great, can't wait for a clear night to test this out...i'm very satisfied with these first results )

Flickr: Luís Campos_astro's Photostream

Greets,

Luís

[Gina]

WOW!!! They're really great images - real crackers Glad you found my posts useful

[Luis Campos]

Hello Gina,

Thanks!

Yup, while searching on the net for ideias for the mod I stumbled upon your thread, really brave you to do the mod

Just a couple questions pleasde, how do you adress the sensor fogging problem? It's not that I hav ethat because I havent tested it yet on real conditions (darn clouds) but suspect it will be a reality, I'm thinking about heating the "air chamber" within the baader MPCC and sensor filter with some welded resitors shrouded on insulating film, I think it will do the trick.

I've been doing some dark images just to test the noise reduction....and it's dramatic to say the least

Thanks in advance for your help,

Greets,

Luís

[Gina]

When I cooled the sensor to give an EXIF T of -7C I did get condensation but it was alright at -3C. So far I've done nothing to stop moisture getting into the camera and then condensing on the filter or sensor. I'm planning to seal the camera with silicone grease and put silica gel pouches inside to absorb moisture. The light path including shutter is open to the main inside space in the camera so the silica gel will hopefully dry that area too. I have a clip-in filter which I hope will stop moisture getting in through the light path.

[martin_h]

My QHY9 has a heated window over the sensor, a circuit board with a few surface mount resistors on it connected to the 12V fan supply.

[Gina]

That's interesting - thanks

[Luis Campos]

Hello Gina,

Thanks for your answer.

That it, let's see if this crazy weather clears and then i'll see if there's the need to aplly the heater into the light path, if necessary it will be a farly easy thing to do

The silica pouches also crossed my mind, i'll also try to incorporate some into the camera just in case

Greets,

Luís

[Luis Campos]

My QHY9 has a heated window over the sensor, a circuit board with a few surface mount resistors on it connected to the 12V fan supply.

Cheers Martin,

Yup, that's more or less the ideia, heating just slightly somewere near the sensor to prevent moisture and condensation, the spot were I take my images gets really damp most of the time so I think i'll need to adress that problem...let's see

Thanks!

Luís

[yesyes]

Hmmm, it seems odd to me to cool the sensor and then heat it again... Wouldn't that also cause stray "light" in the IR range?

[SamAndrew]

If you're using water cooling, you could run the pipes around the focuser to transfer some heat to the front of the camera ?

That would be my approach, keep it simple

[Mr TamiyaCowboy]

Luis will have a lesser problem with fogging, he has insulated the cold finger so only a single part delivers the cooling. notice in his pictures the foam around the metal parts and only the sensor uncovered to receive the finger.

gina's difference is using silver arctic thermal paste as a insulation, but it cools down the whole internals as the finger is unshielded. this is causing the misting/fogging.

cooldown : like a telescope i would allow camera to cool down slowly using a lower voltage to the tec, then adjusting voltage after an inital cooling down period. cooling down slower could allow less fogging. your dumping a lot of cold into something warming up so need to slow down the cooling period over time

[Gina]

Luis will have a lesser problem with fogging, he has insulated the cold finger so only a single part delivers the cooling. notice in his pictures the foam around the metal parts and only the sensor uncovered to receive the finger.

Yes, good idea.

gina's difference is using silver arctic thermal paste as a insulation, but it cools down the whole internals as the finger is unshielded. this is causing the misting/fogging.

Yes, I've been looking at that. Wondering if thermally connecting the main camera frame (which surrounds the internal filter holder) to the hot side would be feasible. I could also thermally insulate the cold finger inside the camera.

cooldown : like a telescope i would allow camera to cool down slowly using a lower voltage to the tec, then adjusting voltage after an inital cooling down period. cooling down slower could allow less fogging. your dumping a lot of cold into something warming up so need to slow down the cooling period over time

Thank you for that - something I hadn't thought of. It looks like 5v would be enough even for initial cooling then. That will be good as I'll be using an ex-PC PSU to supply it. There's even more amps available at 5v that there are at 12v. Not that the TEC takes all that much

With the camera left on the scope in the obsy it will already be at ambient temperature when I start and there would be no problem in applying some cooling before I'm ready for imaging eg. while PHD is calibrating.

I already have the camera indoors ready for fitting the temperature sensor and sealing the case so I can do other mods at the same time. I don't think there's much chance of clear skies any time soon.

[Mr TamiyaCowboy]

hold out gina that nice lump of high pressure will come soon, i hope.

the cooldown came to me last night after sitting with my baby dob on the windowsill doing its usual cooling. then i though fogging/misting and camera.

could go even lower than 5v gina, the psu will also feed a 3.3v but lower amps to use up.

shame could not get 7.2v could run camera of the psu to

reading up on the qhy5 and other qhy models some of those folks are running at -30.

i think summertime will be the greatest test warm air and cold sensor. thats where the key to cooldown is i think with modded DSLR

other dedicated cams are sealed units and purged with gas.

onboard temp gauge could be possible on both cams, local chemists ( £5 in my chemist) sell them cheap digital thermo's, one of these de-housed could be threaded to the CF right next to the sensor ( a foam sandwich to protect from shorting board) then feeding the LCD to the outside and hot gluing in place. saves you gaining it from the Exif T.

[yesyes]

Luis will have a lesser problem with fogging, he has insulated the cold finger so only a single part delivers the cooling. notice in his pictures the foam around the metal parts and only the sensor uncovered to receive the finger.

I saw that and was wondering where I could get some of that foam from. Does someone know what that is called? I can't seem to find anything remotely similar, but I guess I just have the wrong search terms...

[Gina]

I went down to 3.5v on the TEC the other night when I was aiming for -1C so 3.3v might be usable. Yes, I knew the PSUs give 3.3v too. I'll just have to drop the 12v to 7.5 or 8v for the camera - easy enough with an LM317T.

[martin_h]

The QHY software allows a slow cooldown period, other software I use I can set the cooldown period...ie down to -20 over 15 mins, but obviously you need a temperature feedback for that to work properly.

[Mr TamiyaCowboy]

I saw that and was wondering where I could get some of that foam from. Does someone know what that is called? I can't seem to find anything remotely similar, but I guess I just have the wrong search terms...

neopreen (spelling) i think its called buddy, an old wetsuit will give you yards of insulating

your the Wiz gina we just throw the ideas lol, i hope you have copywrites all worked out you could be onto a new wave of supercooling

[yesyes]

just found this foam on Ebay. Would that be the right thing?

eBay - The UK's Online Marketplace

[Gina]

I saw that and was wondering where I could get some of that foam from. Does someone know what that is called? I can't seem to find anything remotely similar, but I guess I just have the wrong search terms...

I have some Expanding Foam Filler that I got from a local cheapo shop. It's Rapide Bond & Fill. It's designed for filling and insulating walls etc. Haven't tried it yet but I'll have a play (away from the camera) and see what it's like. I'll report results shortly

[Mr TamiyaCowboy]

gina it will crack the internals, that expanding stuff is evil.

what you need to find is Neopren sheet ( used to make wetsuits) its like a rubberized foam material. that should work a treat, should stop anything punching through and also act as an insulation, tends to come in 3.5 / 4.0mm thick but can get thinner stuff.

[Gina]

Just squirted it onto a piece of cardboard - looks promising It's an aerosol can of 500ml and cost a fiver. Fills up to 33 litres, it says.

[Mr TamiyaCowboy]

Just squirted it onto a piece of cardboard - looks promising It's an aerosol can of 500ml and cost a fiver. Fills up to 33 litres, it says.

to be honest i would go with OP's idea and use a rubberized foam, a lot safer and saves a decent modded cam.

[Luis Campos]

Cheers all,

Yes, I took extra care on the insulating dept.

My fear of ruining the electronics on a short period due to condensation inside the camera and possible corrosion of the components due to this, made me take this route :/

The material used to insulate is adhesive insulating foam, used on air conditioning materials, easy to get at your local hardware store I guess, I got a 10 meter roll....hey, it's even great to insulate your batteries from cold, they last longer, just make a "dress" to the batteries...lol

My peltier is unregulated at the moment simply cause I don't have a clue of what do to to regulate the power to it....what do you use for this, I must buy some components

Thanks everyone!

Luís

P.s. Yup....like I said Gina is a brave, going fot this mod with no fear he he he

[Gina]

gina it will crack the internals, that expanding stuff is evil.

what you need to find is Neopren sheet ( used to make wetsuits) its like a rubberized foam material. that should work a treat, should stop anything punching through and also act as an insulation, tends to come in 3.5 / 4.0mm thick but can get thinner stuff.

I have some neoprene sheet from way back when I used to go dinghy racing (sailing) and made my own wet suits. Also have various thicknesses of plastic foam sheeting that was used as packaging.

As for the spray foam, I wasn't going to squirt it into the camera - just squirt it onto cardboard or something and then apply the foam to the parts that want insulating.

[Mr TamiyaCowboy]

well gleaning info from gina, she has used a old computer power supply, they let you have 3.3v - 5v - 12v

Miskatonic Institute of Technology: PC power supply modification. ATX PSU hack with regulated variable voltage and LCD voltmeter.

this is a more fancy mod for a psu

a simple way its to bridge two pins so it fools the psu into powering up