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cjdawson

ZWO Peltier Cooler

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8 minutes ago, cjdawson said:

I have sharpcap, but I'm using Sequence Generator Pro for my deep sky work.  

 

Some of your comments are very useful to me...

 

Here's my thoughts.

1. I've not checked this out yet.  Just been doing some starting tests, on this to make sure that it's good to go.

2. Still working on this bit.  I'm trying to tweak my setup to make it work better.

3. I'd thought about this as well.  Would be great to be able to control where the cold is better to stop it going through to the filter wheel.  I'm sure that will help to make the setup work better overall.

So I took this as far as making a plastic fw/camera adapter for the thermal break and I'd got down to -15.8c if my memory serves me - the point to note here is when you actually take the whole thing out in anger and its close to freezing or significantly below to maintain -10 or -15c is quite trivial with single stage cooling - its a big ask indoors at a balmy 23c ambient.  The key to getting the temperature down was good insulation.

I then bought a qhy174m so stopped pursuing this, the additional investment in having a commercial cooling camera is worth it in my opinion, but it was fun tinkering.

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@John78 I hear you about having a proper cooled camera.   I already considered doing that and maybe one day, I'll have the pennies for a an ASI1600 or better.   Right now however, I have to do the best with what I have.   Frankly, I think that even the 12 degree drop that I've achieved so far is good enough to be able to run the camera for real at 0C.    It'll be interesting for me to fire up the camera and see what that actually translates to on the camera's temp sensor.

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Good luck.  I hope you manage to capture some images without cooling below freezing.  I use -30°C for my DSO imaging and still use Darks.  That is with the ASI1600MM-Cool camera.  I shall be interested in how well you do. :)

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Added another rubber gasket to the cooler.   I think I needed this because I used a bigger aluminium block.   Doing another test right now, started at 24.8C and it's down to 6.6C and still falling.   :D

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On 16/09/2018 at 14:53, Stub Mandrel said:

If not, you need to insulate the block between the TEC and Camera all around, even a thin layer of foam. If air can get to the block it will defeat the cooling. 

1 hour ago, cjdawson said:

Added another rubber gasket to the cooler.   I think I needed this because I used a bigger aluminium block.   Doing another test right now, started at 24.8C and it's down to 6.6C and still falling.   :D

I hate to suggest I was right, but I will! 🙂

 

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There I was about to announce that the project was completed any working great.   However at the SGL weekend, I fired it all up to make a dark library.

Worked to start with, however I moved it and think I shorted out the temperature module.   The display went black.  I checked the fuses and they are OK, but the display now gets very hot.      Guess, I'm going to have to get another one off eBay.   oh well.  think I'm going to dismantle the plugs and see if I can add some insulation to make it harder for them to short out.

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On 14/10/2018 at 23:06, cjdawson said:

There I was about to announce that the project was completed any working great.   However at the SGL weekend, I fired it all up to make a dark library.

Worked to start with, however I moved it and think I shorted out the temperature module.   The display went black.  I checked the fuses and they are OK, but the display now gets very hot.      Guess, I'm going to have to get another one off eBay.   oh well.  think I'm going to dismantle the plugs and see if I can add some insulation to make it harder for them to short out.

Dash it (or words to that effect!)

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I seem to remember saying that the image sensor of the uncooled ZWO CMOS astro cameras had a thermal connection to the case but I was wrong - it hasn't!!  The image sensor chip is on a separate PCB connected to the main board with a ribbon cable.  If the case is cooled only air circulation within the casing can cool the sensor.  I found this out when I had a disaster with my all sky camera in a recent storm which ripped the top off the ASC and the rain soaked everything including the camera.  Wet got into the camera causing a short on the PCB and destroyed the camera!

Not only are the non-cooled cameras not designed for any sort of cooling but the image sensor is not in a sealed chamber.  There is no desiccant like there is in the cooled cameras and water/damp can get in around the connectors which are a loose fit in the casing.  The conclusion is that only a minor amount of cooling can be applied with an external Peltier TEC.  Unlike the cooled ZWO cameras which have a sealed imaging enclosure, these non-cooled cameras must be kept dry (and that includes avoiding dew!). 

From experience with my ASC, externally cooling the camera such that the camera data shows a few degrees below freezing is perfectly viable but more than that requires the full ZWO cooling system with a sealed imaging enclosure.  At least any small amount of damp that gets into the camera will condense on the inside of the case and not on the image sensor or front window.

Hope that clears up any misconception I may have created and my apologies for misleading.

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I wonder if you could fit a copper cold finger between chip and case?

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Yes, I wondered that myself.  There is a small hole in the sensor PCB behind the sensor but its smaller than the chip so only the middle would get the full cooling.  I'll take a closer look on my dead camera and see if there's any gap behind the sensor chip.

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There isn't any gap under the sensor chip and there are connections on all four sides.  Whether the little hole in the PCB would be any use for a cold finger I don't know but it's tiny compared with the chip.  I guess the ASI178MM is the same going by the marking on the PCB.  Here are some photos of the sensor PCB.

1242830509_ASI185MMFault02.png.9213e2ea6cd744f4083b2f605f6a9c4c.png735374052_ASI185MMFault03.png.e038b29507dca025e88743dbebe8032f.png2087488144_ASI185MMFault04.png.e027ecd9661c12bfcf32a2e78d7b167a.png

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/////////////////////////////////////////////////////

Sorry about that - double hand lens fell on keyboard 🙂

Might still be worthwhile? Fill hole with heatsink compound then push a copper block in?

I wonder how the ASI 120MC compares?

 

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Might work.  I haven't got an ASI120MC so I don't know what that's like but I would guess it's the same.

Edited by Gina

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Might work better for the 120MC because the sensor is so much smaller.  If the hole is the same size it probably covers a significant proportion of the back of the package.

James

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Don't think I shall be doing anything for a while as I've got a heavy cold and dosing myself with paracetamol to alleviate the symptoms!  :eek:

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Thank you 😀  Been outdoors for some fresh air and feel a bit better.  Decided a walk up the hill might be too much so just strolled around the garden a bit.

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Don't think so - just a heavy cold...

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Unfortunately, there's nothing you can do for colds, except rest, warmth & Hot Toddies....

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Taking paracetamol but not too much.

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