Peltier Cooled C9.25 OTA Container

[asimov]

Progress so far: Made a quick lid out of white packing foam. Stripped the Dork Smith 12V fridge down to its components & installed them onto the lid.

Test run last night showed the peltier will cool to -1.5C if I want it to. My plan is to cool the scope to just below ambient at the time I want to image.

A bit rough looking ATM but thats ok. ;) For those that don't know, the plan is to put the OTA in the box & cool the whole thing.

Edit: The last 2 pics are of the inside of the lid with the cooling plate shown.

[Lester]

Put a patent on that Asi, and you may never have to weld again.

[matt]

Looks good Asi.

Did the fridge come with the fan shown in the pic on the right?

Or did you strap a fan to the heat sink?

cheers:thumbsup:

[asimov]

Well, I need to iron a lot of bugs out first Lester. This in not 'active cooling' so when I take the OTA out of it's box & mount it, & the air temp is still dropping.....I'm going to need another peltier setup on the scope itself. :) It will just need to be controlled so when the ambient drops below 1 deg of the mirror, the peltier cuts in.

The other problem is its all 12V..I'd rather 240V as I will be wanting to run the OTA peltier container 24/7.

[asimov]

Yes Matt, the fan comes with the peltier if you buy the whole unit. After stripping it down, I had to come up with my own way of remounting the fan to the heat sink. 4 screws did the trick. You can't see it in the pics, but the fan & heatsink are separated by 20mm of clear space...Don't want to melt the plastic fan by attaching it directly to the heat sink.

[Robert_T]

i'm watching this space Asi... looking good so far :thumbsup:

[[1ponders]]

Good onya Asi. What temp are you running in the box?

[asimov]

I have not fired her up as a unit yet Paul. But the cold plate on the peltier gets down to minus 1.5C. I don't want it to get that darn cold in there!

So I need more gadgets...240V-12V/3Amp adapter so I can run it off mains supply/an inline timer so I can switch the peltier off & on to control the temp because the peltier has no thermostat control.

[[1ponders]]

Yes the last thing you want is for the scope to get so cold that when you take it out of the box the corrector fogs up instantly. Also if the internal air is colder than the outside it may "suck" warmer moister air inside and fog it up inside which would be worse than no cooling.

Maybe a temperature switch that will interupt the power going to the peltier rather than try to thermostatically control the peltier directly

[davidpretorius]

awesome mate

well done

[asimov]

Yes. A lot of trial & error coming up. Gives me something to do on these cloudy night I guess.

I'm doing sample temperature readings & recording them ATM. Right now its 13.1C outside. 18C in the house. I'd only have to get the scope cooled by 5 degrees right now as an example. The trouble will be all nights are different, may have to be on the ball 100% in order to make this system work....and some systems are not worth going on with.

We'll see.

[AndrewJ]

Gday Asimov

Interesting little project you have going there.
In my last post re dewheaters, i posted some piccies of a
simple one channel microprocessor ( PICAXE tm ) controlled dewheater
i have made. This uses a locally available processor, sensors
and the programming software / hardware is free.
( And easy to learn )
The chip required is about $15 and the digital sensors are about $6 ea.

You program in a form of basic, and this unit can read digital temp sensors and humidity sensors, and can also write to LCDs, back to yr PC etc.
As such, it is a very flexible solution.
Ie it would only be a code change to allow it to drive a peltier unit.
You could then preset an absolute temp to get the box to,
or even
( if used in the real world ) set a temp/ temp delta and
use it as a "reverse" dewheater.
Ie stick a sensor on the mirror and one for the air.
Then program it to keep the mirror at X deg, Xdeg above air etc
Once built, the functionality is all controlled by code,
and if you want, you can watch what its doing on yr PC.

( You said you had cloudy nights to waste :) )

Andrew

[asimov]

That sounds like the ultimate solution for controlling what I have in mind Andrew, thanks mate! I'll look into it.