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Canon 1100D Cold Finger Peltier Cooling - WIP

russellhq

By russellhq
in DIY Astronomer

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russellhq

russellhq

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I've run into a bit of a problem with the LCD. After I soldered up all the sockets and put everything in the box, the LCD lights up but doesn't display anything. I checked all the connections for continuity, shorts and voltage and all looks OK. I re-loaded the LCD program and the Arduino seems to be working correctly, it just seems there's something wrong with the LCD circuit. So a bit of head scratching for now!

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russellhq

russellhq

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I've run into a bit of a problem with the LCD. After I soldered up all the sockets and put everything in the box, the LCD lights up but doesn't display anything. I checked all the connections for continuity, shorts and voltage and all looks OK. I re-loaded the LCD program and the Arduino seems to be working correctly, it just seems there's something wrong with the LCD circuit. So a bit of head scratching for now!

Not sure if this is the problem but I removed the LCD unit and noticed that Pin 1 and Pin 3 are connected together when I tested them with the multimeter.

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russellhq

russellhq

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Made a little more progress today. The control box is pretty much finished, I ordered a replacement LCD and it worked straight away, therefore I must have blown the last one some how.

Here's the box and connectors with the arduino running the "Hello World!" LCD example script. I also made up the 8 pin connector cable as well.

IMG_20140522_184246.jpg

Connectors on side of control box for various sensors and power:

IMG_20140522_184220.jpg

Inside the box. It was a bit of a tight squeeze.

IMG_20140522_184400.jpg

Another shot of the sockets.

IMG_20140522_184456.jpg

A surprizing amount of time actually went in to building this. One of the trickiest parts was routing all the wires and attaching the sockets! I'm glad that's done now. :)

Next stop is adding the 8 pin socket and USB socket to the coldbox and wiring up the power and sensors inside the coldbox.

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russellhq

russellhq

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Thanks Gina, thanks Ray.

It was tough getting everything in the box, it took a lot of planning. And I was paranoid that something might short circuit, hence all the heat shrink sleeves. I could have finished a lot sooner if I'd used a bigger box, but with how it turned out, I'm glad I didn't.

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russellhq

russellhq

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Nice work. Now I want a smaller control-box as well. Thanks a lot  :tongue:

I'm curious on what delta temperature you get.

At maximum power (13V), it was achieving just over 30C delta at a room temp of 20C and a coldbox humidity of around 13%. I've still to run further tests and to test it under load from the camera as well.

The heatsink and TEC I'm using are oversized for the job, I would like to get a smaller set-up for the final set-up.

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Gina

Gina

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Nothing wrong with that Russel :)  I got much the same.  The big problem I found with keeping the bayonet mount was sealing the box well enough to prevent ingress of damp.   I shall be working more on this problem before long as I'll be producing an OSC cooled astro camera as well as a debayered mono.  1100D OSC and 1000D mono is what I have in mind, having failed miserably to debayer an 1100D sensor without destroying it.

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russellhq

russellhq

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Nothing wrong with that Russel :)  I got much the same.  The big problem I found with keeping the bayonet mount was sealing the box well enough to prevent ingress of damp.   I shall be working more on this problem before long as I'll be producing an OSC cooled astro camera as well as a debayered mono.  1100D OSC and 1000D mono is what I have in mind, having failed miserably to debayer an 1100D sensor without destroying it.

Thanks Gina. An initial, short, test showed a +5C difference between the RAW file camera temperature and the cold finger temp sensor. I'm not sure how close I should expect them to be, but 5 sounds a little high. I'll be running more tests to see if it improves as I believe things were still cooling down when I ran the test.

Yes, keeping the humidity out is a big problem, at the moment I'm using teabags filled with desiccant :)

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Gina

Gina

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The EXIF T value included in the RAW data is obtained from the image processing chip and not the sensor so its value can be quite different from the actual sensor temperature.  I think the cold finger temperature may be closer to the actual sensor temperature but will be lower because the sensor generates heat.  I wouldn't like to guess by how much though.

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Davey-T

Davey-T

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The EXIF T value included in the RAW data is obtained from the image processing chip and not the sensor so its value can be quite different from the actual sensor temperature.  I think the cold finger temperature may be closer to the actual sensor temperature but will be lower because the sensor generates heat.  I wouldn't like to guess by how much though.

Help !!! can't for the life of me find a temperature setting in the Exif data. :)

Dave

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Davey-T

Davey-T

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No, it isn't :( You need other software to read it such as APT or some image editing/displaying software

Have downloaded Rawdigger but not the first time I've been annoyed by lack of available info in Canon software.

Dave

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russellhq

russellhq

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has anyone made a working template for the cold finger they can share?

Your best bet is to mock one up from cardboard first before trying to make a copper one.

I bought a piece of 300 x 100 sheet of copper 0.55mm thick from here:

http://www.ebay.co.uk/itm/400653926080

And I bought some plastic sheet 0.5mm thick to make an insulating barrier between the copper sheet and circuit board to avoid short circuits.

http://www.ebay.co.uk/itm/400653926080

Total cost was about £6. 

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elenhinan

elenhinan

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Thanks Gina. An initial, short, test showed a +5C difference between the RAW file camera temperature and the cold finger temp sensor. I'm not sure how close I should expect them to be, but 5 sounds a little high. I'll be running more tests to see if it improves as I believe things were still cooling down when I ran the test.

Yes, keeping the humidity out is a big problem, at the moment I'm using teabags filled with desiccant :)

I get about +3 to +5C from my sensor to raw file temperature as well. I think my delta T is around 20-25, running at 70% with 60mm fan at 5V.

I'm looking into Magic Lantern for the time being, seeing if it's possible to tweak the ISO/gain values to get better SNR for astro (as they do for normal photography), or hopefully turn off the dark current compensation. In my notes I didn't see a big difference in noise from -10C to 0C, but looking at the top optical black part of the sensor I see some difference. Trying to figure out why.

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russellhq

russellhq

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I was considering adding a port (1/4" schrader valve) to the box that I could attach a dry gas source to. I could then run some dry gas (Air, N2) through the box to bring the humidity down and then disconnect. This should last for at least an imaging session if the box has a good seal and has desiccant inside.

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