Just finished fabricating a cold finger to fit a Canon 450D. It will also fit the 1000D, and from what I can see, the 500D.
The CF fits around all the hardware, except for the side cover on the USB/video port side of the camera - unless the camera owner is happy to remodel it - tape is just as effective and less destructive.
The zip/.dxf file is the template shown in the images.
Materials - 1.2mm copper sheet.
Tools - bench vice, centre punch (optional), steel rule, scoring tool, drill and 2, 3 and 4mm bits and a small file.
Method of working - print template, check template for correct scale, cut out and fix to copper, scribe outline and cutouts and fold lines, centre punch holes.
Drill 2mm mounting holes - these align with the sensor frame 2mm tapped holes.
Drill out cutouts with 2, 3 and 4mm drills, file square.
Bend as instructed on template and keep them tight. Most important - the two middle bends when complete should be no deeper than 5mm, one side to the other, as shown.
I cut out the notch in the wrong position and had to widen to fix - access to sensor ground connection screw.
EDIT: The bends are easy enough to do in a bench vice. Line up the score mark with the top edge of the vice. Place a flat metal/wood plate behind the copper to apply even pressure (don't use thumbs and fingers). Bend to right angle. The middle bend can be a fiddle. A spare bit of 3mm aluminium plate placed between and flush with the top of the vice jaws, slightly longer than the sensor end to avoid crushing it, as shown. It's important to clamp the copper both sides to get a good sharp bend. Radii on the bends don't work - the finger won't fit.
Where can I get the copper sheet? I have a laptop cold finger system that I hope to make use of at some point.
I have a 450D so this is very interesting. Do you know where the temperature sensor is located on the 450D?
Glen. I buy copper sheet from here, but it is also available on ebay - 1.2mm is just right, with a layer of clear packing tape on the pcb side.
You will need a heatsink in the order of 120w to get a decent differential.
I don't know where the temperature sensor is located. I don't reference it because it doesn't tell you anything useful - no relation to the actual sensor temperature - which is true for the 1000D. Whether that is true for later models, I don't know. The closest estimate of sensor temperature is the cold finger.
Here is an exiftool dump of one of a series of images taken at -5C cold finger temp. Given that frost will form on the sensor face if not protected, 12C exif bares no relation to the temperature of the CMOS, or the associated electronics on the backing PCB.
In real terms exif is of no practical value to the DSLR cooling mod. The file is one of 200 bias frames taken in one sitting to produce a superbias.
EDIT: Despite using the same cold finger pattern for several years I think cutting a large swathe out of the middle section might improve performance, as long as there is adequate metal for a cooling pathway to the sensor tongue.
It might be helpful to follow the link in my signature to see what I have done with the second prototype.
There is very little room for insulation and I recommend a ceramic roof paint dip if desired.
The real work centres around the protection of the sensor and electronics - no changes there.
Attachment is 2 x plastic 2mm screws into the sensor frame and a narrow strip of double sided glue tape near the side cover as the finger exits the camera. This is very stable and absorbs shocks. Essentially, except where necessary insulation is air gap.
If you are interested there is also a newly developed electronics package to control all of this.
EDIT: It is probably worth noting that there are two schools of thought on cold finger mods in relation to keeping the sensor face free of condensation 1. Sealing. 2. using a low power heating element. I use the latter, because it is easy to implement and effective. You could try sealing the camera hermetically and using dessicant. You would need to seal all incoming and outgoing cables and use an external power source to avoid opening the battery compartment. Tethered shooting, laptop and so on. I find all of this inconvenient and cumbersome.
A cold finger will provide temperature differentials at the sensor in the order of 20 - 30C depending on design. And there is the option of temperature regulation. The latest iteration when complete will have a real differential of 20 - 23C, allowing for sensor face heating. The modified cooling algorithm smoothly maintains +/- 1C at the temperature sensor, with a resolution of < 0.3C. I imagine the camera sensor/cold finger/PCB total mass will fluctuate less, be less dynamic, due to its thermal mass. Real time, regulated cooling.
No pictures yet, but I have implemented a number of features on the MK5 prototype (1000D), in preparation for the battery grip housing - waiting on the boards to arrive. Besides tightening up and smoothing cooling control and increasing the resolution of the temperature sensors, it now has an OLED displaying a bunch of very useful data. I can finally see what's going on. The lens dew heater is now controlled by switching through a MOSFET.
A word on dew control. I have had to think outside the square, because I wanted to avoid dismantling the camera any more than I felt necessary, to attempt major sealing modifications - it's just a DSLR with moderate, but perfectly adequate cooling capability, spending most of its time operating at -5C.
I have employed four basic strategies for the prevention/control of condensation;
1. Provide a small external area of cooled metal exposed to the air, close to the point where the cold finger enters the camera; that is, the back of the metal plate that clamps the cold finger, TEC, heat sink assembly.
2. Seal electronics in areas of significant cooling, as a safeguard; that is, the PCB attached to the sensor.
3. Fit a small nichrome wire heater element to the periphery of the sensor face. The prototype output is currently fixed, but can be variable with the use of a humidity sensor.
4. Dew strap/straps strategically located on the camera lens. Lenses are typically not weather proofed and the base of the lens tends to cool in contact with the camera, which gets quite cold.
Insulating the camera body is an exercise briefly explored with 5mm neoprene, but I found it promoted condensation and complicated handling. Clear shrink wrap might be an option?
Anyway, the methods above do not require major modification of the camera and work surprisingly well.
Thanks for the update Rowland. I have the copper for the cold finger now, but I cannot open your dxf file. Is it possible to get the simple dimensions of the finger in mm? I could work it out by opening up my 450D again but would like to avoid that till necessary because its on the scope this week being used for imaging. Specifically the width of the finger to fit between the contact rows of the sensor board. Also you mentioned 2mm plastic screws attaching the cold finger to the sensor frame (I assume) but why plastic, as internal camera screws on the frame are metal - unless you do not want to earth the finger? Thanks for the development work on this solution.
Glen. I will upload a file with dimemsions. I use plastic screws to reduce conduction to the sensor frame - I do all I can to isolate the CF. In theory, the screws will break under load, rather than twist things out of shape, if the camera is dropped. The finger must be grounded if using a TEC system. I'm not sure the Canon screws are long enough? The top of the cold finger sits about 3.5mm higher than the EMI shield screw down points. Personal preference? 2mm deep colletts are needed under the cold finger to support the CF.
Prior to filling the cavities created by the sensor pins to PCB gap, isolate the edges of the CF from the pins with strips of plastic - or some other means.
Prior to filling the cavities created by the sensor pins to PCB gap, isolate the edges of the CF from the pins with strips of plastic - or some other means.
Rowland thanks, I am thinking that I will coat the entire cold finger (with the exception of the sensor contact patch area) with boat building epoxy (specifically International HT9000). Epoxy encapsulation has been used for many years and if the right epoxy is used (not the five-minute stuff from Bunnings which is hydroscopic over time) it will insulate the finger very nicely and can be applied thinly by brush. Once encapsulated the finger should not need additional insulation across the rest of the internal area (but I will test that), and it should reduce the chance of condensation inside the camera. Outside the camera the finger will be open for condensation trapping.
The copper finder will need to be solvent cleaned and 'keyed' with fine sandpaper to allow the epoxy to form a good bond to the surface. I am also considering coating the entire upper sensor board with epoxy as opposed to hot glue or other substances, as it will be more durable and only a thin coat would be required.
Sounds good Glen. I might follow your lead on the insulation. It gets tight, with just room enough in places, particularly if you want to locate a sensor between/underneath camera parts.
Attached CF dimensions. from the original dxf file. Note: Think about adding 5mm or so as indicated. While the CF fits more room is advisable to access the various ports along side the CF.
Glen. Please let me know if you find anomolies with the CF dimensions - suggestions for improvement. While, I am sure that it will fit without a hitch, please verify before cutting and bending.
Made a start on the cold finger today. Rowland there are a couple of dimensions I need, for the cutouts - how far are they from the nearest side of the finger?
Is the L shaped cutout 5.6mm wide?
I can't tell from the last drawing.
Glen. the L is 5.6mm at the base. And, I see what you mean, that 4×7 cutout? Will measure up when I get home this evening. I use the template. The base of the L from the nearest edge, too! I will update the CAD file and post in a friendly format.
Rowland my next question has to do with the copper clips on the side of the frame and sensor boards that hold the two boards together. I can't work out how to get the finger in there when the clips are in place? What did you do with them?. One of your photos from your other thread:
seems to indicate that you just glued the whole thing together with silicon, is that correct?
I could shorten the finger to get the right hand side frame clip on the chip but that means reduced surface area on the chip. It's impossible to get the clip to fit over the finger to hold it and the chip board (well maybe if I bend it flat and cut it alittle it might fit).
If you look at Gary Honis' instructions here (Step 21 on this page)
Glen. The copper retainers are removed. The sensor is located by two lugs into the sensor frame, and these hold things in place while inserting the cold finger - until such time as the 2mm screws are in place. You will need, as mentioned, 2mm deep collars around the screws for support, between the bottom of the cold finger and the sensor frame. Essentially, replacing the role of the copper retainers. So, yes the assembly can come apart in your hands, but I find the lugs hold things together quite nicely - I will look at pointing this out in the instructions.
Quickly knocked up a side elevation looking toward the cold finger exit point. I have a spare sensor on hand and the PCB EMI cover is attached at four points to the sensor frame. Very secure once all together.
Thanks, that explains it. I assume they are PCB spacers. I will make something from stuff I have. Getting there I believe. Ignore the sloppy metal work, no vise or things to make the job easier, it fits and no one is ever going to see the cutout and bends. This is a temporary placement to check clearances and the screw down of the finger. I think I will just use metal screws and that way don't have to worry about earthing the finger.
Progress photos attached.
Looking good Glen. One suggestion, only. Check that the usb/remote board will fit back in place, cleanly, before fixing and sealing the copper finger. If not, sharpen that second bend. You can use metal form work a hammer/mallet to punch it into shape - aside from a vice.
