MarsG76

As I was exposing last night, I noticed that one of the peltiers isn't working, so one peltier was all that was used with a heat sink and fan on the other side... Temperature wise it didn't seem to make so much difference, if any... but I might have had a faulty/open circuit peltier from the beginning... Do peltiers fail easily?

Yeah, I figured that the heat sink might be too small, but so far the result is OK with the fan overkill shown above. Another mod I might do later is place a thick piece of copper between the peltier and the heatsink to increase the gap between the heat sinks and the copper plate, and fill the gap with expanding foam, which is (allegedly) the best temperature insulator outside of a vacuum that is easily available.

Having to solve the heat feeding back problem, I decided to put another peltier/cheat sink on the other side of the copper plate and styrofoam in between the heatsinks and the copper. I built a simple circuit board to power to the fans and the temperature controller as well as a relay circuit which supplies power to each of the pletiers through a relay, separating the current flow per veroboard track as initially having the total of 11.8 amps for both peltiers on one track did fry it. As the heatsink fans are blowing air into the heatsinks, I also added two fans on the top and bottom of the heatsinks to speed up the extraction of the heat within. Now the temperature drop was 10 degrees and stable, as reported by the NTC, but after a while I saw moisture forming on the exposed cold finger so again I'm guessing that the temperature was a lot lower than around the 16.5 degrees that the temperature sensor was showing. This test was performed inside during a warm evening, so for dew to form on the copper I imagine that the temperature was closer to the 5 degree mark. OK, it was time for another dark frame test, again gain was ISO1600 but this time I'll expose the dark frames for 1800 seconds, which is the time I generally spend per sub for my narrowband imaging. I did another dark sub test with the top fan blowing into the heat sinks for comparison. The result was substantial.... What this shows is the darkframe comparison uncooled to cooled with, first, the top added fan extracting... than with the added fan blowing into the heat sink. This is a comparison to subs on the left which are RAW unprocessed with all of the noise intact. Photoshop CameraRAW does reduce noise as it converts to TIFF, and does a pretty good job of it, as shown in the center, As a final step I pre-process the subs with a "Dust & Scratches" filter to remove the individual pixels which were left by CameraRAW... 2 pixels @ threshold 30 did a good job of only removing the noise/overactive pixels resulting in subs with the noise level shown down the right side. These are the subs I would normally stack. All of these pictures are center cropped 640x480 from the original files. The orientation of the top fan made little difference but by having both fans extracting the warm air, it seems to have had the edge and so that how I'll keep the fans for the final version. I started doing some wide angle imaging, mostly as a test. The wide angle subs are 120 second subs at ISO 1600 and so far the results are awesome... my subs are noise free. Next clear night I'll image some long exposure narrowband subs through one of the scopes. Since the current state of the setup has cables, the circuit board and temperature controller hanging down and held in place with alligator clips, I'll have to clean up the whole cooled DSLR setup into a nice package with only needing to plug in the power supply. I might also try to move the temperature probe into a place where it'll report a more accurate actual sensor temperature. So far I'm very happy with the results. Clear Skies, MG

Hello All... Thanks everyone for your help and info during my cooling mod of my DSLR. I do believe that I had a bit of success. The cooling worked initially but as the heatsink heated up, it in turn heat up the copper plate and as a result the peltier was in a loop trying to cool itself... ultimately the temperature dropped around the 10 degree mark but soon rose 5 degrees and that's where it stabilized. Even though the temperature drop was not great, I did do a dark frame test... This was the result of uncooled and cooled ISO1600 darks... 24 vs 19 degrees. I did allow it to cool for 20 minutes before I exposed the cooled sub. The exposure time was 30 minutes on relatively cool night... so there is a bit of a difference in the amount of noise in the raw dark subs. Eventhough there is a drop in the noise level, its not enough..... Note that the actual temperature drop of the sensor might be lower than reported since the NTC proble does not sit on the sensor or the cold finger.

Hopefully it ends up being a success and helps others thinking about this take the plunge into cooling their DSLRs.

Apparently the EXIF sensor is a bit of distance from the CMOS so there is slight a difference in reported temperature vs actual temperature so.... .. I placed a NTC sensor directly on the CMOS so this might show a bit more accurate temperature...

Absolutely.. my next stage is the insulate the heat syncs from the copper plate by inserting a piece of aluminium between the peltier and the copper plate on both side to increase the gap and fill out the gap with first Styrofoam than perhaps expanding foam as a final product is the styro insulates the heat away from the copper and stops it from heating it up....

These are the 30 minute darks (800x600 center crops) at ISO1600 one with cooling turned off and the second with allowing the camera to cool for 20 minutes and exposed for another 30 minutes also at ISO1600. There is a slight improvement but not major...

Thank you for the responses... It looks like I need to insulate the back of the exposed copper with foam and get a bigger heatsync and fan to continue. The peltiers only drain 5.85A even if the PSU can supply 50A.... so the PSU is (hopefully) sufficient. Do you think that using a second peltier and heatsync/fan combo on the other side of the copper plate where @Stub Mandrel is insulating with foam is overkill, or even counter productive?

Attached is the heatsyncs I use, this was when I had only one on the copper plate, now there are two back to back... I'm doing the cooled test and comparison now... the NTC sensor which I have inside is reporting 19.4°C but there is some dew on the plate, so it has to be lower... After allowing them to cool, I took a 10 second dark which reported a EXIF temp of 25°... Once this 30min cooled dark is finished I'll compare...

Hi Louise, The peltiers are 30x30mm TES1-12703... and the power supply is a 12V 50A... I'm sure that 600W is more than enough... current drain per peltier is 5.85A.

@Stub Mandrel Today I attached the peltier and heat sync... the internal sensor only reported a 6° drop in 30 minutes.... hardly worth it... so I added another peltier-heatsync combo to the other side of the plate.. 7°!! What da??? Im hoping that the internal probe I placed on top of the sensor is inaccurate so now I'm doing a ISO1600 30 minute exposure with cooling off than allow it to cool for 20 minutes and do another 30 min ISO1600 sub while cooling... this will show me whether the project is worth the trouble...

I was planning on keeping the sensor around the 0 degree level or just above the dew point if that caused a problem..... I wasn't planning on going below, or far below zero... but thinking about heating the front of the sensor with the dew heater controller might make it possible to go as far below zero and physically possible.... Mind you tho.. down here, the nights during summer are around the 20 degree make, so even if I could go 20 degrees below ambient, I might not reach freezing point... winter can be moist and below 9 degrees tho....

Hi, Covering the connectors, thank for the tip, I was going to do that of course..... I inserted another temperature probe inside the 40D, sitting just above the sensor, hopefully this will give me a good ball park figure of the temperature... this probe will be connected to the temperature controller which will turn on/off the peltier to keep the sensor between the upper/lower set temperature. If the above measures fail to keep the front of the sensor dry, I will wrap and glue some nichrome around the front of the sensor frame (as suggested by @Stub Mandrel, match the resistance of my dew heater strips and connect it to my Astrozap dew heater controller. I figure that the IR cut filter is removed so there is a few millimeters gap to play with for the wire and glue around the front of the sensor.

The other anti sensor dew counter measure is wrapping a dew heater strip around the T-Adapter around the front of the DSLR... that might keep it dry also....

Nice project, well done of your success... as far as the PCB location on the 40D is concerned, it's in the same position as on your 450D, and the cold finger needed to go between the sensor and the main PCB. @Thalestris24 got me thinking more about the dew/condensation on the electronics so I ordered a can of "Conform Coating" to cover the PCB to help with the moisture. As far as covering the PCB in hot melt or glue for insulation, that is not an option since the thickness of the glue would far exceed the amount of space between the components, it's already tight, let alone with a few millimeters of the melt on the board, so I thought that the conform coating is a better option. My other plan is to keep the cooling just above the dew point as I do have a unit in the observatory that shows the temperature, humidity and the dew point temperature. My question to you is regarding the nichrone wire around the sensor. Was the nichrome wire around the sensor necessary due to the sensor actually frosting over in practice or was this a preventative measure? Reason I ask is because I added two peltier coolers to the sides of my DMK41au02 CCD, which were running uncontrolled and even though there was a heap of condensation dripping off from the CCD, the actual sensor remained dew and frost free... I put it down to the sensor generating some heat, heat rises as the camera is orientated upwards, this being enough to keep the front of the sensor dry.... flawed? Generally the coldfinger works like the peltiers on the case of the DMK41, ie secondary heat extraction via a medium, and on the DSLR only 1 peliter being used. If the need for the nichrome was needed due to actual frosting of the sensor, did you power it via a dew heater controller or just run it of a 12V uncontrolled source? What is the resistance of the nichrome around the front of your sensor? Looks like there's a bit more to think about with this project than initially anticipated....

I was thinking about that, but I'm under the impression that condensation (ie distilled water) won't conduct. I'm more concerned about the rust on certain parts.

Hi All, I finally had a chance to start my active cooling mod of my astro modded Canon 40D. Initially I started with designing the shape of the cold finger and creating a to scale template on paper... I made two designs, one with bends around the sensor, and one which is mostly flat with minimal bends. I went with the latter since I figured that I will not be able to bend the copper plate with such precision using my available tools... ie two pieces of wood. I cut out the cold finger on the copper plate and after bending the cold finger into shape, I realized that there was a bit of a gap between the copper and the sensor... ...so I cut out a piece of copper 1mm smaller than the sensor on each side and inserted this in between the cold finger and the sensor. Hopefully (with the use of heat transfer paste) creating contact and being more efficient in extracting the sensor generated heat. I used the existing screws to hold the cold finger in place, three screws should be secure enough to hold it in place. Now that the cold finger is in place, it is time to put the camera together. There is not much room inside the camera and so the mod is very tight. The main PCB is a tiny bit offset and inserting the compact flash card is tighter than normal, as is inserting the mini-USB cable. At this time I was expecting the camera not to power on but... ... it's alive... ALIVE!!! I've taken a shot of the light without a lens and the white frame tells me that the sensor still works. There is enough room to use the side connectors as needed. The most important connectors are the USB connector which will be used almost exclusively and the remote trigger connector which I'll use when I'm not using the laptop. Part 2 of the cooled DSLR mod is a success, all that's left now is to bend the outside plate 90 degrees to the front, install the peltier cooler, heat sync and the temperature controller.... Clear skies, Mariusz