ASI120MM cooler

[John78]

Due to a of darkness lately, I've been putting together a cooling system for my ASI120MM.  It consists of 2x 12706 72w peltiers stacked on top of each other...

http://www.ebay.co.uk/itm/1-10-x-TEC1-12706-Heatsink-Thermoelectric-Cooler-Peltier-Plate-Module-12V-6A-72W-/252283854943?var=&hash=item3abd4a205f:m:mLvIqMaxwjAuZsSQcBIhPWQ

An Arduino nano controlling 2x IRFP350 n-channel FETs using the PID library, an intel heatsink and fan from an i7 processor, and a 3d printed adapter plate to attach the cooling system to the camera.

I wrote a script which sends (from sharpcap) the temperature of the sensor via serial to the Arduino which then PWM's the FETs to apply the power to the TECs.

Now I'm not convinced stacking is meant to work with 2 like units - but after some experimentation, I apply full power to the top unit and 1/6th power to the one touching the camera body and I can get about 20 degrees below the ambient without much insulation on the camera body (the cover for the insulation is on the printer now).

 

Here is a 15 second dark at nominal settings ... 22.2c

And another dark, same settings but ... 2.7c 

 

So clearly cooling works, its blacker and less noisy with cooling.

 

Issues still left to contend with are -

1.  The i7 heatsink doesn't fully cover the hot side of the TEC

2.  The whole camera gets soaking wet (the insulation is WIP)

3.  How to get colder (ideally with less power) - I had hoped to be achieving -20c

4.  How to fabricate a thermal break between the camera and the filter wheel

 

The temperature sensor inside the ASI120MM is a bit naff, slow to update and 0.7c resolution, so I might go back to the original plan of using a DS18B20 sensor read directly into the nano.

 

I'm not too keen on the heat-sink and fan arrangement - I think a discrete water cooling solution would be preferable and probably an order of magnitude more effective, so that might be coming next......

Sharpcap script.txt

Capture_0001.CameraSettings.txt

Capture_0003.CameraSettings.txt

[Gina]

The 12706 Peltier cooler is extremely inefficient - you want a much lower power one and then you only need one.  I used this method to cool an ASI185MC camera in one of my all sky camera builds.

[John78]

@Gina I read through your entire cooled camera thread but you didn't mention what your cooler actually was - do you have the part number or any further information on it?

I need to add a window heater to keep it clear - so a couple of watts, then the camera so I'm assuming something like a 10w unit would be a good choice??

Digikey seem to have the biggest range of TEC's - there's like 653 to choose from...

https://www.digikey.co.uk/products/en/fans-thermal-management/thermal-thermoelectric-peltier-modules/222?k=peltier

When you say the 12706 is extremely inefficient, is that due to its power, design or the fact its an elcheapo Chinese knockoff out of a mini fridge??

 

edit : I did see digi key sell some modules that will fit in this configuration...

http://astrofotografia.republika.pl/ASI120MMmod.htm

Which is pretty nice - shame they are £25!!