Hi folks,
Finally, well almost have my newly modded and cooled DSLR up and running!
Tell you what, that was real fiddley stuff! Looking at the tutorials etc on doing these mods you don`t realize how small alot of these connectors are!
One thing I have learned also was DON`T USE SUPERGLUE! Some people mention to use super glue but on drying I found the superglue left hazy rings in the corners of the Baader filter. Had to rush into town and get some Acetone to clean off the superglue, and what a hastle to remove the filter again from the frame. Instead used some black silicone which worked ok but took forever to cure. Next time I will use some 5min epoxy. Getting the filters spotless was also a challange as everytime you got one clean and put it aside to do the other, those dust spots would appear again. Got it almost dust bunny free except a few in the bottom corner which only show up a high F/ numbers.
Next I fixed a copper cold finger to the back of the Cmos and cut a slot in the plastic side cover under the usb connector. Not much room but managed to squeeze it in with a few layers of electrical tape for insulation.
The cooler is a old AMD cooler with a 4amp TEC running of a 12v supply. Still havn`t made the control box to regulate the TEC but have all the components ready to assemble. Not sure how accurate the controller is but was told it was accurate to 1C.
Gave it a quick bench test to see how it all runs at 22-c and after the cooler was running for 15min....See attached pics.
Shall get it finished in the next few weeks hopefully.
Have to work on any dew problems as yet..any thoughts appreciated!
Thanks for the inspiration and help Martin!
Always wanted to try this !`m glad I didn`t kill the sucker!
Shall update when the control box is up and running. Hopefully I can keep the Cmos down to 0c
cheers Gary
Awesome stuff Gary love the designed shape of the copper bit, how thick is that Gary. looking forwqrd to the tests mate
Leon
Thanks everyone, Good to see you dropping by Leon, pitty not to see your cold box in action. The copper plate is .7mm thick from a hobby store. Had some 0.5mm aluminum just incase it was too thick.
Hooked up the temp controller for a quick test and the cold finger easily gets down to -4c with the ambient temp sitting around 22.5c. The controller can be set for high and low temp but can`t set it to less than 2c between the two. Will go to -20c at max. I think I would run into probs trying for that..
A modest 0c sounds pretty good to start....
Hi Gary - Courageous indeed to delve into you Canon with such a mod!
But tell me - if you get your cold finger down to -4 degrees and your ambient is at 22.5 then isn't there a danger that you are cooling below the dewpoint and that you may get condensation on your CMOS imager or within the camera? Cheers Peter
Gary it looks like you didnt isolate the cold finger at all.
That way you ask for trouble, moisture will stay on uncovered metal and this way also on the chip.
This way it will end up on your components.
It is better to put some tape on top of the cold finger and thin silica gel bags in every part they will fit.
It is best to leave a part of the cold finger outside of the camera bare so the moisture will settle on that part and not in the camera.
You could also spray the circuit boards with a circuit board laquer so moisture doesnt short out anything that easy (that is what i did before the mirror motor burned out), this way i could go to -7C.
The ccd cameras sold have the boards with a layer of laquer on it and the bare parts of the cold finger is used to collect the dew that is still there.
Hope this helps a bit.
Hi Gary - Courageous indeed to delve into you Canon with such a mod!
But tell me - if you get your cold finger down to -4 degrees and your ambient is at 22.5 then isn't there a danger that you are cooling below the dewpoint and that you may get condensation on your CMOS imager or within the camera? Cheers Peter
Hi Peter,
Most probably will get condensation, was just a quick test so didn`t have time for the dew to build up. I have yet to make a silicone dissecant system for the camera to suck out the moisture. Next part to do .
Quote:
Originally Posted by mill
Gary it looks like you didnt isolate the cold finger at all.
That way you ask for trouble, moisture will stay on uncovered metal and this way also on the chip.
This way it will end up on your components.
It is better to put some tape on top of the cold finger and thin silica gel bags in every part they will fit.
It is best to leave a part of the cold finger outside of the camera bare so the moisture will settle on that part and not in the camera.
You could also spray the circuit boards with a circuit board laquer so moisture doesnt short out anything that easy (that is what i did before the mirror motor burned out), this way i could go to -7C.
The ccd cameras sold have the boards with a layer of laquer on it and the bare parts of the cold finger is used to collect the dew that is still there.
Hope this helps a bit.
Thanks Martin, The cold finger is totally insulated, I just took the photo after I cut it out. It has two layers of electrical tape over it and a little foam tape under it on the left of the cmos as well. Also electrical tape over the ribbon connectors to the cmos as well..Didn`t take a pic then but.
cheers Gary
Should be ok then
The only thing left to do now is putting some small silica gel bags in the camera to keep it dry, and your off.
Oops: and some cloudless and moonless nights to test it
Good idea about getting some small silicone bags in there..must be real small ones but. Thanks Martin.
Now clear and cloudless...them things are rare lately!
Gary you are a brave man and your work is brilliant!
I just lately have been looking into peltier cooling, even bought one the other day to test it out but it seems I need a bigger heat sink and fan. Early days for me yet.
I seen Martins mod at snake Valley which got me interested.
Just wondering if any fan vibration may have any effect on images?
Great work
Just wondering if any fan vibration may have any effect on images?
Daniel - all the best CCD's on the market employ fans of varying size and speed to aid in their cooling, most of these fans (that I've seen anyway) are no different to your standard computer fan. At least with the DSLR mod, you have the choice of what fan you want to use, and if the camera is purely for astronomy use, there is no reason why you wouldnt opt for a bigger than usual fan that runs at lower voltage to produce the same CFM (Cubic Feet per Minute) rating... There are two advantages of a larger fan, and one disadvantage...
Advantages:
1 : Larger fans can move the same amount of air and lower RPM & voltage than a smaller fan, and therefore can create less vibrations.
2 : They are quieter.. (this seems like a big case of "Who cares?" until you are sitting out on an imaging field with something like the Orion Starshoot Pro cameras. They have a 40mm fan that runs at very high RPM and sound somewhat like a dustbuster... when its happening all night on a relatively silent imaging field, it gets REALLY annoying..) An 80 to 120mm fan would be the go if you can facilitate it.
Disadvantage :
1 : It can be hard to implement a large fan into a design that looks even remotely elegant on a DSLR body...
Function over form I always say.. Who cares what it looks like as long as it does the job efficiently, quietly and satisfactorily.
Thanks guys, my DIY skills are quiet modest really, just have to do plenty of research like right here on IIS and the net and source the bits and pieces you need. Still waiting for some Artic silver to arrive and a poly box for the control box and the power supply to run it all.
As for the fan, never had a problem with vibration at all. I have a simple peltier and heatsink/fan that I have attached to the bottom of my cameras since I had my 300D to keep it a bit cool in summer and has never affected the image what so ever. Have higher speed fans to move more CFM but opted for a quieter one which is also thin. Seems to do the job.
Just wieghed the cooler assembly and comes in at 460 grams.
Glad I didn`t use a copper heatsink! even though I reckon it would make a difference.
Shall post some more pics as I get closer to finishing it off.
I've been thinking about the mechanics of silica gel bags inside a camera and wondering about the effort involved in checking and drying them.
It occurred to me that it should not be all that hard to keep the silica gel outside the camera and have it in the flow path for a positive pressure system. A small tube fed into the camera body could keep the internal pressure above atmospheric and the silica gel could be in the incoming airflow path. It then becomes easy to check the state of the silica gel and to dry it as needed. If power is not a restriction a largish peltier in the incoming airflow path might also be useful.
I've been thinking about the mechanics of silica gel bags inside a camera and wondering about the effort involved in checking and drying them.
It occurred to me that it should not be all that hard to keep the silica gel outside the camera and have it in the flow path for a positive pressure system. A small tube fed into the camera body could keep the internal pressure above atmospheric and the silica gel could be in the incoming airflow path. It then becomes easy to check the state of the silica gel and to dry it as needed. If power is not a restriction a largish peltier in the incoming airflow path might also be useful.
Bob
Good info Bob... thanks
Was thinking of something similar...giving some positive pressure sounds like a great idea!
This is what I might be going to do....
Drill a hole in the side to insert a tube which is attached to a film canister or similar container which has a tube running to the warm side of the heatsink where the fan is pushing air. Was thinking the warmer slightly pressurized air would flow through the container into the camera.
Would you think that could work?
Or my second thought would be similar but no flow through just the silica enclosed in a container connected into the camera via a tube?...
Gary I think you would need some positive pressure to stop moist air getting in elsewhere. Warm air can hold more moisture than cold (hence the tendency for dew to form as it get's colder). http://www.engineeringtoolbox.com/mo...air-d_281.html .The warm airflow might be counter productive where you are feeding into a deliberately cooled system.
I'd considered suggesting running the airflow over a peltier to try and cool it a bit before it hit's the silica gel but don't have the experience with peltiers to know if are powerful enough to add value. Years ago I used to work with both silica gel and what was called a drycol unit to dry the airflow through the breathers in power transformers. My recollection is that the drycol unit ran the air over chiller plates to take the moisture out of the air.
Gary the ideal would be to bleed in pure dry nitrogen or dry air from a compressed 'bottle'.
I would get one of those fish tank airators and pass the flow over a cold Peltier surface to get rid of the majority of the water vapour and then through a container with silica gel or molecular sieve pellets. Both of these can be regenerated by heating in an oven. A vacuum oven works even better. The Peltier cold trap can be regenerated by allowing it to warm up and drain any water.
The flow rate does not need to be high only high enough to produce a dry positive pressure inside the camera. A focal reducer or filter immediately in front of the camera would really help to stop 'warm' moiste air from getting to the sensor. Any slight leaks would be easily compensated by the internal positive pressure and low flow.
I would try at first to keep your sensor temperature above the dew point.
I have measured the temperature of my sensor in the 5DH and it is 17C above ambient when continously exposing.
When my fridge Peltier heat exchanger is set at -10C the fridge interior is at -5C and the sensor is at 12C. Without the fridge and at 20C ambient say the sensor would be at 37C!
Since you are cooling your sensor directly I would start off at about 15C for the sensor and slowly work down until you get condensation.
You will be amazed how much the thermal noise is suppressed even when running your sensor at 15C.
Finally bit the bullet-Cooled modded 40D v1
!`m glad I didn`t kill the sucker!
