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Canon 1100D Cold Finger Peltier Cooling - WIP


russellhq

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Maybe it's time I produced an abbreviated thread of my 1100D strip down for astro, including removing all the unwanted parts and modifying the top section ribbon cable so that none of the top section is used other than part of the ribbon cable.

I second that!

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Cold finger Mark V

IMG_20140511_201004.jpg

The plastic protects the sensor circuit board from shorting on the copper.

Here it is mounted on the sensor. Notice that there's a small part of the circuit board poking through the cold finger. I had to drill a hole to accommodate this as it was preventing me from getting the cold finger close enough to get access to the mounting screws.

IMG_20140511_200931.jpg

Here's a couple shots of it mounted on the sensor assembly and camera frame. The other holes allow the cold finger to be located in place to keep it away from the sensor legs.

IMG_20140511_201425.jpg

IMG_20140511_201440.jpg

I used 0.55mm copper sheet to make this. It was far easier to work with than the 1.2mm sheet and also allowed me to get the plastic sheet in as well.

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Here's a couple of photos of the 450D one I did.  I haven't done an 1100D one yet but I think it's the same.  I will check though.

post-13131-0-75924600-1399837901_thumb.jpost-13131-0-12359400-1399837910_thumb.j

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Here's my interpretation of the 2 pictures. I've marked what you did in red and what elenhinan did in blue. Look's like elenhinan added 1 more bridge:

post-6495-0-25182900-1399838715_thumb.pn

Also, I've some silver conductive paint lying around. I reckon that would work just as well as solder?

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You could try it :D  I don't think these connection carry much current.  If you ruin a ribbon cable I'll send you a replacement - I've quite a collection :D

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You could try it :D  I don't think these connection carry much current.  If you ruin a ribbon cable I'll send you a replacement - I've quite a collection :D

Thanks for the offer Gina, I hope I don't have to take you up on it!

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I bought some LM2596 boards to do my voltage conversion:

http://www.ebay.co.uk/itm/370975230952

I was hesitant to put the MOSFET and voltage converter inside my box as it would only add to the generated heat. But maybe it's an insignificant amount.

If I put the MOSFET and the LM2596 inside the box, I would then need to feed the following cables:

1: +12V (Common power)

2: Common ground

3: Data1: Cold Finger Temp

4: Data2: Box temp & humidity

5: Data3: MOSFET Gate PWM

 

I'm also thinking maybe I should have the TEC on it's own socket (phono) and have the data and voltage lines on another socket (e.g. 4 PIN DIN). I like your idea of the zener though. I'll need took look those up to see how to use them.

 

I'm running the box on test at the moment. Currently getting RH 14% and delta T of 35C :D I'm happy with that.

I'm sure I'm making a meal of these cables, but here's my current thoughts:

1. Have a small project box to house: Nano, LCD and Voltage Regulator for camera

2. Have 1 off 12 V supply going to project box to power all devices

3. Have a separate cable for the TEC power that is spec'ed for the current between project box and cold box

4. Have a cable carrying the data lines for the cold box sensors and camera power (5 PIN DIN is likely candidate)

5. Have a cable for the fan power and heat stink sensor (not sure what type, but I only need 3 connections. Was thinking 3.5mm stereo jack)

6.Mount a USB B socked onto the cold box for camera connection (like to be this: http://www.ebay.co.uk/itm/371053113901 )

3 cables between the project box and cold box sounds a mess, but I don't see a way around it. My concern about using ribbon cable is if it will handle the current (currently using a 6A TEC)

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I have had problems with DIN connectors in the past - they are very poorly made as a rule.  I have changed to XLR multi-pin connectors for astro use as they are professional connectors with a high spec.  They have latching clips too so don't fall out.

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Nice to see your work progress :)

My solder of the ribbon cable looks messy, as I had to desolder everything when my camera stop working as part of the troubleshooting. So solder all over the place. Anyway, your guess at where the lines are at looks correct. It's easy enough to see when you look at the back side of the selector plate-thingy. I've marked the planes that should be grounded with a black dot.

Also, remember to set the flash to off in the menu of the camera if you remove the flash-open detector. This can be done through USB as well, so no LCD is necessary. Else you won't be able to do 1/4000s for bias, and there might be other nasty side effects as well.

I bought some ip68 din connectors, but in the end I only used one in the control-box end. Reason being that I could not find a (cheap) waterproof (airtight) usb connector panel mount for the camera box.

I use one 8 wire cable (old serial/rs232 cable) for both data, voltage rails, ground and TEC power.

2 wires for camera vcc and gnd (dedicated)

2 wires for common ground including TEC

1 wire for 5V to sensors and fan (fan speed is ok at 5V).

1 wire for humidity data

1 wire for temperature data

1 wire for TEC VCC

At the control box end, everything is common ground anyway. The data lines only read data every 1 second, so interference at the sensor readout should be negligible, TEC power should be well filtered dc, so no noise there either. Ideally. Maybe I should measure it some day.

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Also, I inserted a dc-adapter into the battery bay. This shorts the middle pin to ground (I think), which the camera detects as being connected to DC. Difference being that auto-shutdown is disabled then, but this can be done through the menu as well.

The camera looks like it have 3 voltage rails on the mainboard, with linear voltage regulators and filters for each. So my guess is that even a bit noisy DC power for the camera would not affect the image quality. At least I didn't see any difference in bias noise between battery and dc power.

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Thanks elenhinan. I'm getting there... slowly. I took another delivery of parts yesterday so should be able to make more progress.

I also have the dc adapter for the camera and was planning to use it to for connecting up the power.

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Nice to see your work progress :)

My solder of the ribbon cable looks messy, as I had to desolder everything when my camera stop working as part of the troubleshooting. So solder all over the place. Anyway, your guess at where the lines are at looks correct. It's easy enough to see when you look at the back side of the selector plate-thingy. I've marked the planes that should be grounded with a black dot.

Also, remember to set the flash to off in the menu of the camera if you remove the flash-open detector. This can be done through USB as well, so no LCD is necessary. Else you won't be able to do 1/4000s for bias, and there might be other nasty side effects as well.

I bought some ip68 din connectors, but in the end I only used one in the control-box end. Reason being that I could not find a (cheap) waterproof (airtight) usb connector panel mount for the camera box.

I use one 8 wire cable (old serial/rs232 cable) for both data, voltage rails, ground and TEC power.

2 wires for camera vcc and gnd (dedicated)

2 wires for common ground including TEC

1 wire for 5V to sensors and fan (fan speed is ok at 5V).

1 wire for humidity data

1 wire for temperature data

1 wire for TEC VCC

At the control box end, everything is common ground anyway. The data lines only read data every 1 second, so interference at the sensor readout should be negligible, TEC power should be well filtered dc, so no noise there either. Ideally. Maybe I should measure it some day.

Also, did you have any concerns running 2A though the old RS232 cable? From what I've read it doesn't look like it's designed to handle that much current!

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I too think 2A would be too much for a single wire though some older serial cables were a lot thicker than later ones.  When I use multi-core cables I double up on high current lines and have used three for Gnd where interference can result due to wire resistance producing coupling between circuits.  Separate ground lines are a good idea as elenhinan has used (where this is possible).

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I too think 2A would be too much for a single wire though some older serial cables were a lot thicker than later ones.  When I use multi-core cables I double up on high current lines and have used three for Gnd where interference can result due to wire resistance producing coupling between circuits.  Separate ground lines are a good idea as elenhinan has used (where this is possible).

Probably a daft question, but do you also double up the ground cables on the high current lines?

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OK, decided to go with 4 cables.

First will be dedicated TEC power. This will just use phono connections between coolbox and control box.

Pin 1: +12V

Pin 2: PWM GND (or maybe just GND, see further down)

Second will be USB cable for fan power and heatsink thermocouple. I'll add a USB socket to the control box and use a USB cable with the end cut off wired up to the fan and thermocouple.

Pin 1: +12V (or +8V)

Pin 2: GND (or maybe PWM GND if I want to slow the fan down, not sure)

Pin 3: Data Thermocouple

Pin 4: GND

Third will be USB cable for camera data between coolbox and PC.

Fourth will be the camera power and coolbox sensors cable. I came across these GX16-8 connectors after endlessly searching and they seem to fit the bill.

UC302-1.jpg

This will give me:

1: +8v Camera Power

2: GND

3: +5V Humidity Sensor Power

4: GND

5: Data Humidity & coolbox Temp

6: GND

7: Data Temp Cold Finger

8: GND

Although I might ditch the +5V in favour of a Data PWM TEC line and put the MOSFET inside the coolbox...

Hopefully get some time this weekend to work on it.

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Tried to get some 8 core cable for the data/power connection between the coolbox and control box and ended up having to get network cable. Are there any conventions I should stick to when wiring up the twisted pairs?

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So some more parts arrived on Friday, so I think I have enough now to finish the build.

First part is the USB connector for the coolbox:

IMG_20140518_101037.jpg

IMG_20140518_101019.jpg

This should form an air tight seal, but just to be sure, I'm going to use epoxy to fill in the gaps and seal everything up.

The other part is the connector for the main cable to the coolbox. Here is the plug and socket screwed together with the locking ring:

IMG_20140518_101056.jpg

Here's the panel socket, both sides:

IMG_20140518_101115.jpg

IMG_20140518_101125.jpg

So, I'm trying to squeeze all this into a small project box, though I think I'm being a bit ambitious!

IMG_20140518_101149.jpg

IMG_20140518_101254.jpg

IMG_20140518_100943.jpg

This rats nest of wires took me most of yesterday to assemble! Now I need to connect them up to all the sockets, switches and LCD display and squeeze it into the project box  :eek:

Along the way while building this I noticed a couple of peculiarities. First was the zener diode I bought which was rated as 5.1V. But when I wired it up in a test circuit, the multi meter was only reading around 4V (with and 8V source and 12V source and 4k7 resistor).

Second was the volt setting for the camera voltage. My AC adapter was rated as 7.4V out, but when I put the multimeter on it, it was reading 7.95V, I then checked the battery and it was 8.35V. I'm sure I read somewhere that someone set their home made adapter to 8V, so I've decided to go with 8V.

Finally, my best buy of this project has been this guy. This has saved a lot of time and burnt fingers!

IMG_20140518_104117.jpg

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Ah - a sealed USB through connector - that's a good idea :)  Didn't think of that :D  Been thinking of various ways of getting USB to the camera in the dry box for my all-singing-all-dancing camera unit.

Your project seems to be coming on very nicely :)  My projects are definitely on a go-slow :D  The "helping hands" is a great piece of kit - I find it invaluable :)

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Ah - a sealed USB through connector - that's a good idea :)  Didn't think of that :D  Been thinking of various ways of getting USB to the camera in the dry box for my all-singing-all-dancing camera unit.

Your project seems to be coming on very nicely :)  My projects are definitely on a go-slow :D  The "helping hands" is a great piece of kit - I find it invaluable :)

Thanks Gina. I got it from ebay:

http://www.ebay.co.uk/itm/371053113901

I reckon you could fill the socket with epoxy to guarantee a seal (obviously not in the usb socket that is :D)

Got the board wiring finished and plugged in the arduino. It works!!

IMG_20140518_143444.jpg

Next on the list is to cut a hole in the lid, I always hate doing this when it's not just a nice round hole, there doesn't seem to be an easy way to do it!

Once that's done, I need to wire up all the plugs, attached the heat shrink sleeves and then build the a core cable. Next then will be adding the sockets to the coldbox and I should be almost there!

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Next on the list is to cut a hole in the lid, I always hate doing this when it's not just a nice round hole, there doesn't seem to be an easy way to do it!

Following these threads with interest, got my old 450d waiting to be attacked.

For cutting odd shaped holes in project boxes I use a Starrett cutter to take out the main bulk and then finish with an old steak knife heated with a gas torch to melt out the rest.

Dave

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