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MarsG76

DSLR Active cooling MOD process - Part 2

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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...

 IMG_5700.JPG.606075ffc5186c9fc5749b0cbe357498.JPG

 

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.

IMG_5701.JPG.943e15dd8ca4feb3d2ab741afeadd47b.JPG

IMG_5702.JPG.f4c40aa5c4db75f8e68630dc1877e172.JPG

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...
IMG_5704.JPG.23b71730394635899ac3e2e0d9507e47.JPG

 

...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.
IMG_5703.JPG.f8accbdba1bcd07054286382ad190df5.JPG

 

I used the existing screws to hold the cold finger in place, three screws should be secure enough to hold it in place.

IMG_5705.JPG.bcc4dbca0d74b0885cfb8d63f45bf44c.JPG

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...

IMG_5707.JPG.17ea0b725fd921968110c3c85d2a6ea4.JPG

... 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.


 IMG_5709.JPG.dffad047a138bf612a93c734101f542c.JPG

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

 

 

 

 

IMG_5708.JPG

Edited by MarsG76
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Hi

You probably need to spray/coat the pcbs to prevent problems with condensation :)

Louise

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2 hours ago, Thalestris24 said:

Hi

You probably need to spray/coat the pcbs to prevent problems with condensation :)

Louise

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.

 

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Very cool Mariusz.  Very cool indeed (figuratively and literally!)  Keep us updated.

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Nicely done.

Not sure if the 450D has a different sensor arrangement, but I had to push my cold finger between the sensor and a PCB above it.

Don't be depresses if the EXIF shows only a small temperature reduction - the image sensor is well away from the temperature sensor.

I covered all my electronics in hot melt to prevent moisture getting in and add a bit of insulation. Any insulation you can add to the uncooled parts of the cold finger will help a lot. I used a 3D printed cover for the back of the coldfinger, filled with foam.

I had to fit a nichrome wire around my sensor cover glass to stop it getting condensation/icing up.

 

Coldfinger 2.JPG

Edited by Stub Mandrel
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3 hours ago, Stub Mandrel said:

Nicely done.

Not sure if the 450D has a different sensor arrangement, but I had to push my cold finger between the sensor and a PCB above it.

Don't be depresses if the EXIF shows only a small temperature reduction - the image sensor is well away from the temperature sensor.

I covered all my electronics in hot melt to prevent moisture getting in and add a bit of insulation. Any insulation you can add to the uncooled parts of the cold finger will help a lot. I used a 3D printed cover for the back of the coldfinger, filled with foam.

I had to fit a nichrome wire around my sensor cover glass to stop it getting condensation/icing up.

 

Coldfinger 2.JPG

 

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....

 

 

 

 

 

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33 minutes ago, MarsG76 said:

 

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.

Hi

If you spray a coating on remember to tape over all the cable connectors first :)                                                                               

I have a cooled mono 550d (sadly not working for a few years) that I used to set the temperature to +5 deg which seemed good enough. I don't know where the set point temperature sensor is located - I imagine it's  fitted close to the sensor.

Louise

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5 hours ago, Stub Mandrel said:

Nicely done.

Not sure if the 450D has a different sensor arrangement, but I had to push my cold finger between the sensor and a PCB above it.

Don't be depresses if the EXIF shows only a small temperature reduction - the image sensor is well away from the temperature sensor.

I covered all my electronics in hot melt to prevent moisture getting in and add a bit of insulation. Any insulation you can add to the uncooled parts of the cold finger will help a lot. I used a 3D printed cover for the back of the coldfinger, filled with foam.

I had to fit a nichrome wire around my sensor cover glass to stop it getting condensation/icing up.

 

Coldfinger 2.JPG

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....

 

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2 minutes ago, Thalestris24 said:

Hi

If you spray a coating on remember to tape over all the cable connectors first :)                                                                               

I have a cooled mono 550d (sadly not working for a few years) that I used to set the temperature to +5 deg which seemed good enough. I don't know where the set point temperature sensor is located - I imagine it's  fitted close to the sensor.

Louise

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.

 

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1 hour ago, MarsG76 said:

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?

I got a thick layer of hoar frost on the front glass of the sensor.

I took this as a good sign - the sensor itself must be well below zero to do this, backed up by a minute level noise (other than a few hot pixels) in my darks.

Recently the wiring for one of my three paralleled dropper resistors fell off and even with 2/3rds the normal heating thr sensor gradually misted over. I had to experiment a fair bit, I wanted the lowest possible heating current that kept the sensor clear on a damp night. I suspect CCD's are better sealed than DSLRs.

Neil

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10 minutes ago, Stub Mandrel said:

I got a thick layer of hoar frost on the front glass of the sensor.

I took this as a good sign - the sensor itself must be well below zero to do this, backed up by a minute level noise (other than a few hot pixels) in my darks.

Recently the wiring for one of my three paralleled dropper resistors fell off and even with 2/3rds the normal heating thr sensor gradually misted over. I had to experiment a fair bit, I wanted the lowest possible heating current that kept the sensor clear on a damp night. I suspect CCD's are better sealed than DSLRs.

Neil

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....

 

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@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...

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1 hour ago, MarsG76 said:

@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??? 

Don't use the camera sensor, miles from the imaging area.

I just put an NTC sensor on my cold finger where it enters the case. After five minutes the temperature was pathetic, about 11C, peeled back the foam to take a look and there's ice forming on the cold finger....

I seems the sensor needs to be intimately fixed to the cold finger to be accurate.

 

Also... a BIG heatsink and a decent fan are essential.

Edited by Stub Mandrel
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49 minutes ago, Thalestris24 said:

Hi

What peltier do you have and what power supply?

Louise

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.

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7 minutes ago, Stub Mandrel said:

Don't use the camera sensor, miles from the imaging area.

I just put an NTC sensor on my cold finger where it enters the case. After five minutes the temperature was pathetic, about 11C, peeled back the foam to take a look and there's ice forming on the cold finger....

I seems the sensor needs to be intimately fixed to the cold finger to be accurate.

 

Also... a BIG heatsink and a decent fan are essential.

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...

IMG_5742.JPG

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1 minute ago, MarsG76 said:

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.

I typed this before seeing your photo:

 

You need a BIG heatsink.

That's at least 140 watts to dump, so to keep the heatsink no more than 10 degrees above ambient you need a 1/14 = 0.07 degree per watt heatsink.

The temperature of the finger is cooling below the HOT side of the peltier, not ambient, this means you need to dump the relatively tiny amount of heat in the camera and all that power you are putting through the peltier. You need forced cooling to keep the hot side as close to ambient as possible.

If the heatsink is inadequate you will actually heat the cold finger! It can be better to use a less powerful peltier if your heatsink is too small.

I use a 40W peltier, with a big heatsink and an 80mm fan.

Having seen your picture - what insulation do you have on the back of the cold finger? it doesn't look like much. I have a 3D printed box, filled with foam, and all exposed copper is foam covered.

Coldfinger 3.JPG

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35 minutes ago, MarsG76 said:

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.

That is far to high an input power for the Peltier TEC.  I used a 15v 2A one from Farnell Element14 (running on 12v and drawing 19W) and got the temperature down to well below freezing.  OTOH, exhaustive testing on a Canon EOS 1100D showed no noise improvement below -5°C and only a little between 0 and -5.  With the modern ZWO CMOS cameras the cooling is effective and I have used -10°C effectively with external cooling.

Edited by Gina
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I think I've had more success with cooling reducing noise.

Here are two-minute master darks from DSS, both from a similar number of frames, one cooled, one not. It's fairly easy to see the difference by the histograms. Even if you moved the lower point on the uncooled one so they were equally black, you can see there is much more noise

 

image.png.a31a65f2ddbce1f0030388718171a83c.pngimage.png.9eed60dbd3793d0ba8df56aab4e6b403.png

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54 minutes ago, Stub Mandrel said:

I typed this before seeing your photo:

 

You need a BIG heatsink.

That's at least 140 watts to dump, so to keep the heatsink no more than 10 degrees above ambient you need a 1/14 = 0.07 degree per watt heatsink.

The temperature of the finger is cooling below the HOT side of the peltier, not ambient, this means you need to dump the relatively tiny amount of heat in the camera and all that power you are putting through the peltier. You need forced cooling to keep the hot side as close to ambient as possible.

If the heatsink is inadequate you will actually heat the cold finger! It can be better to use a less powerful peltier if your heatsink is too small.

I use a 40W peltier, with a big heatsink and an 80mm fan.

Having seen your picture - what insulation do you have on the back of the cold finger? it doesn't look like much. I have a 3D printed box, filled with foam, and all exposed copper is foam covered.

Coldfinger 3.JPG

 

34 minutes ago, Gina said:

That is far to high an input power for the Peltier TEC.  I used a 15v 2A one from Farnell Element14 (running on 12v and drawing 19W) and got the temperature down to well below freezing.  OTOH, exhaustive testing on a Canon EOS 1100D showed no noise improvement below -5°C and only a little between 0 and -5.  With the modern ZWO CMOS cameras the cooling is effective and I have used -10°C effectively with external cooling.

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?

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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...

IMG_5743.JPG

IMG_5744.JPG

Edited by MarsG76

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22 minutes ago, MarsG76 said:

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?

That would work.

For now just block it with a towel or similar and see the difference.

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Good thermal insulation of the cold parts makes a lot of difference.

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FWIW my 550d showed temps of 12 to 15 deg (filename) in a batch of 14 x 600s darks. The cooler was preset to +4 deg. So a difference in temp of 8 to 11 deg from the internal value. Unfortunately I don't know for sure what the ambient temp was at the time. They were taken indoors in the afternoon in March 2016 so ambient was probably around 15-20 deg. So clearly, with the cooling on, the actual sensor temperature was quite a bit different from the reported internal camera temperature.

Louise

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I used a digital thermometer device directly on my cold finger close to the image sensor.

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