This outlines the procedures and steps I took to modify my Canon 350XT with a Peltier cooler. This is to be considered a guideline and if you choose to follow it you do so at your own risk.

Before attempting this modification, you should have at least a basic knowledge of electronics and circuits to facilitate troubleshooting if something doesn't work once completed.

There are a couple of good sites to use as a guideline for the camera disassembly this procedure is the same as if you were spectrally modifying the camera but stopping short of removing the CMOS sensor these links are provided here Ashs's Modified Rebel XT and Gary Honis's 300 mod .

I decided I would employ a cold finger and Peltier unit for the cooling. My original TEC was obtained from a power chill cooler I had laying around which was a 40x40x4mm and pulled an amp draw of 2.5 @ 12vdc most of the images depict this tec but after testing I found the heatsink I wanted to use was not sufficient for cooling this size TEC so I sized and ordered a new smaller TEC unit from Custom Thermoelectric the unit I went with is a 25x25x4.7mm with an amp draw of 1.5 @12vdc and can be viewed here TEC

The camera disassembled and the rear of the CMOS chip exposed and copper clips removed.

I decided I wanted to design a compact and asthetically pleasing enclosure for the TEC unit. I picked up a small ABS project box from Radio Shack to use for the housing project box.

I placed this along the left side of the camera where the unit would mount and following the top contour of the camera cut the box to match, using the leftover part of the cut off box I cut out the top piece and attached using ABS glue available at Home Depot or plumbing supply houses, and once dried I sanded the seems to look clean.

The next step was to begin design and construction of the cold finger. Using a piece of 1/16" thick by 1 1/2" wide flat Aluminum stock ( obtained from Lowes), with the enclosure lined up to its mounting position on the camera measurments were takin to cover the entire CMOS chip and then enter the rear of the enclosure take a 90* turn and left just shy of the width of the heatsink, allowing depth to mount the Peltier to the heatsink and leave room behind for running wires back into the camera. This image shows test fitting, I made another piece about 1/2" longer and also cut the hieght of the finger down to match the hieght of the CMOS chip.

The next step was to remove the mounting posts and tracks along the inside of the project box to create no obstacles inside of the box this was done using a Dremel with a sanding cylinder.

I decided I would relocate the circuit interface to the bottom of the enclosure since this area of the camera would be covered by the enclosure ( the video and the remote shutter interface)

this is done by removing the 2 small screws securing it to the camera chasis.

Now that this board is being relocated the small wiring harness is to short to reach from the bottom of the enclosure to the camera board so we have to extend these wires, using as small as I had laying around 30awg wire I cut the middle of the camera wires one by one as to not confuse them and soldered extensions on to them this is a little bit of a tedious job.

You have to be very carfull with handling these small wires as they are delicate in thier attachments to the plugs.

The next step was to seal each solder joint then wrap the whole assembly with heatshrink.

We then need to install 2 grounding wires to the mounting screw locations of the interface board to be extended back into the camera and installed to the chasis at the existing screw locations for the board. This is done by soldering 2 leads to the board at the screw locations.

Next we drill a small hole in the rear of the enclosure to allow these wires to pass through and back into the camera. We next mount the interface board into the bottom of the enclosure making sure the plug receptors are set at a depth to allow a cover piece to be put on here, we also install the power plug for the TEC and a small thermistor with leads coming out of the bottom of the enclosure and extended to be attached to the finger on the chip side directly next to the CMOS chip. I placed duct tape over the interface board to protect it form the insulation procedure. the interface board was secured using 2 small screws directly inot the bottom of the enclosure.

I was pondering removing and extending the mini usb port to mount to the right of the interface board in the enclosure but by this time I was already picking at this for almost a month and just wanted to finish this up so I cut out and then heat welded an area on the enclosure to allow me to access the mini usb.

Next came test fitting to make sure the extended wires had clearance to inside the camera, a small area of the chasis had to be cut and folded back to allow the extended interface wires to pass through under the cold finger this was done using tin snips and pliers.

We also had to cut out the side moulding area of the camera which covered the interface board, just cutting out the full thin part of this area to allow all wires and the cold finger to pass through.

Next we assemble the Peltier coldfinger and heat sink cleaning the surfaces of the heatsink, and the cold finger as well as both sides of the TEC with regular rubbing alcohol, allow to dry and apply thermal paste to all bonded surfaces I used Arctic Silver paste, using a small piece of stiff circuit board we drilled and tapped the board and the heatsink and secured the assembly together, next step was to wire it all up.

after wiring up we begin installation of the cold finger TEC assembly to the enclosure, I placed duct tape over the edges of the Peltier again to protect from the insulation process.

Once the assembly is together it was secured to the housing using a small thin metal clip screwed into each side of the enclosure passing through the center of the heat sink.

Next comes the insulation part for the TEC housing using regular expanable foam it was inserted through the rear of the housing (you only need a squirt or two do not over do it!!)

Again I will note that the TEC unit seen in the pictures is not the unit I ended up using..but all installations for it are excactly the same.

Once the foam was set it was time to test the completed unit the test results (these results are with the proper sized TEC that was ultimatley used) showed very promising numbers, a 35* F temp drop in 15 minutes of run time from ambient

Ok now that the TEC assembly is complete we need to install the side moulding back onto the camera, you will not be able to access the screws with the enclosure in place.

Now we place the enclosure up to the camera in it's mounting location, installing pipe insulation tape to the chip side of the finger from the enclosure to the edge of the CMOS chip and embedding the thermistor as close to the chip location under the insulation tape leaving about a 1/4" overlap at top and bottom of the finger to allow a good seal when installing the insulation on the back side of the finger.

Next we enlarged and tapped the top and bottom holes that were used to secure the left copper clip to the chip and drilled the cold finger to match these locations and secured the cold finger to the camera chasis via two small screws and secured the right side of the finger utilizing the copper clip.(thermal paste was applied to the CMOS chip and finger before securing).

The next step was to apply silicon sealant (regular clear GE) all around the CMOS chip and the chip frame and then install pipe insulation tape to the back side of the finger.

Once the sealant has dried it is time to reassemble the camera (and hope everything works!!)

Reassembly is the reverse of the dissasembly with a small mod to the left side mounting posts on the rear bezel of the camera these need to be cut off now that the screws are already installed for the side bezel, the back piece is still secure on the left side by the bottom screws. You should note that this is a tight fit now due to the insulation on the finger you will get some small flexure on the cameras rear circuit board when reattaching it but not enough to cause concern.

Here are the completed images along with dark frame comparisons

Using a leftover piece of the ABS housing I cut and heat welded a cover for the interface board.

Dark comparisons, the first image is at 71*F Ambient 10 minute exposure at iso 1600

The second image is with the TEC running for 20 minutes same exposure 10 minutes at iso 1600

These images were only 100% center cropped and converted to jpg.

This was a moderatley complex modification and if you decide to undertake it good luck and take your time.