To build my cooler box I've been following Gary Honis's design, using aluminium sheet to build the box and peltier cooling module.
I have seen many boxes that have been built following that design and planned to make my own modifications to improve the box and cooling even better. In the next steps I'll cover it all.
I ordered Aluminium Sheet from HERE and Peltier Module with heatsink HERE.
I have carefully measured the size of the box and cuts for camera on the paper first, then cut it out from the aluminium sheet.
For additional internal heatsink I will be using heatsink from old GFX card.
To bend the box with nice 90 degrees angles I have used couple of wooden planks and hammer.
To fasten the sides of the box I have drilled small holes in each corner and used rivets. After that I polished box and heatsink surfaces with small grit sandpaper.
Next, is the most important thing in building the box and it's thermal insulation. I have used adhesive foam insulation sheets, which have very strong adhesive and very easy to cut with scissors.
For the box to be effective, it should be completely air tight. And those adhesive foam sheets are just perfect for that too.
To help it with being air tight, I have glued previously cut piece of foam inside of the box, so when you attach EOS ring from outside, it will press the camera upon that foam and will prevent air leaks from inside and outside.
To make sure, I decided to go with double layer of insulating foam. And being it that easy to cut, I could make specific cuts for my equipment and in my case these cuts were made for OAG.
Digital Thermometer will be installed on the outside to help monitoring the internal temperature of the box.
I went with double layer of adhesive foam all around the box. On the bottom I had to create deepening in the foam for OAG to fit.
Also on the bottom, where camera would be fastened to the box with the screw, I have inserted large metal shim between the layers to have more area pressing against the bottom of the camera.
To keep lid closed tight to the box, I'm going to use two welcro strips on the front and on the back of the box.
It is also important to separate the hot heatsink from the cold surface of the box, so there won't be heat transfer between those sides and will help to keep the box cooler.
I have used the same adhesive foam to fill the whole square area of the heatsink. The heatsink from old GFX card were cut to required size and would be installed inside of the box, on the cold side of the peltier.
I couldn't use double layer of foam to separate the heatsink from the box, because it would be much thiker than the peltier and would prevent good contact for both sides.
So for the additional insulation I have used aluminium insulating tape around peltier, covering the whole are of the heatsink.
The heatsink is large, it have 92 x 92 mm area.
The Peltier I have used is 12703 version that would draw 3 Amps, which is meet my whole battery capacity for the full night run.
As for the lid of the box, I have used additional aluminium sheet that were cut to the size of now completed box. Since I have used double layer of the foam on all sides of the box, the box became larger so the lid were cut to cover that whole area.
On the bottom side of the lid I have used double layer of the foam that were cut to the exact inner size of the box. This part will go inside the box it self and create "stairs" which will help to prevent air and cold leaks outside.
On the bottom side of the lid I have used additional layer of aluminium tape, to better insulate and help keep cold air inside.
To prevent the cold air leaking outside of the box even better, I have used small foam strips inside of the box at exact height were bottom side of the lid would be. That would create additional "stairs" when lid would be closed.
As for the camera connection with EOS ring, I didn't want that the box would touch the EOS ring and transfer cold to the OAG and further.
So I have used the same adhesive foam to stick it all around the EOS ring, which will prevent it from being in contact with cold box openning.
All the same it will prevent air leaks too.
To attach the Peltier to a box and it's heatsink I'm going to use one of the best thermal componds outthere, it's Shin Etsu x23 thermal paste.
And to prevent from humidity to build up inside of the box I'm going to place inside a small box of rechargeable Silica Gel that I grabbed for cheap on ebay. Works just great.
This is the final layout. The internal heatsink attached inside of the box just behind the camera sensor.
Small fan placed on the same side close to the heatsink to help circulate the air.
On the right side is the black sensor of thermal digital sensor that would monitor the inside temperature of the box.
Small Silica Gel pack is placed just becide the camera.
Taking the image from the front shows how the internal heatsink placed exactly behind the sensor.
To help in fast cooling of the camera I have removed the backplate with it's LCD screen. This is very effective, since nothing will trap the heat inside of the camera and everything would be exosed to a very cold air.
This is how the camera fit inside of the box. All nice and tight leaving just a small volume of air to be cooled.
From the closeup shot you can see how back of the sensor is very close to the heatsink that would radiate the cold. It's not a cold finger of course, but I think that that way, I have fully maximised the cooling possebilities of the box.
Here you can see how nicely my OAG system with CCDT67 reducer (under the cap), fits the box.
Here is the wire arrangements and I have placed a simple switch that would turn on and off the Peltier and heatsink Fan together.
On the other side, I have attached the digital LCD screen to monitor the temps and additional switch to turn on and off the internal circulating fan and the LCD screen together.
This is useful for example in the morning, when I want to open the box for some reason, I turn OFF the Peltier and leave the internal fan and temp. screen ON. Then I wait when internal temperature rises to the outside temps and I know that it is safe to open the box without causing the moisture to build up inside.
Now the fun part - the actual test.
I turned the LCD and internal fan first and let it run for couple of minutes to have temperature to stabilize inside of the box.
Then I turned the cooling ON when inside of the box were 24° C.
After half an hour the temps were dropped by 15°.
After one hour the temps were dropped by 18°.
Two hours later the temps were dropped by 20°C below the ambient !!! I were really surprised and very satisfied with the results.
During the next imaging runs, I've noted that the EXIF temperature reading of the camera, after 15 minutes exposures, consistently showed the temperature of only 4° C above the box's temperature.
For example, if box's reading were 4° C, then after 15 minutes exposures, frame's EXIF readings would read
8° C.
There was the first winter night with the box , when the ambient temps were around +7 +8° C and my box got as low as -8° C !!! Frames after 15 minutes exposures were -2, -3° C.
The cooler box does he's job exceptionaly well.
To demonstrait the cooling impact on the image quality I've made two single shots of NGC206 Star Cluster inside the Andromeda Galaxy, each were 15 minutes of exposure.
Here is the one without Cooling and with EXIF reported temperature of 35° C :
And this one is the same 15 minutes of exposure but with Cooler Box turned on and with EXIF temps reported only 8° C. I think the difference speak for it self:
