previous experience with peltier cooling was for a peltier
cooled greyscale webcam that I built. I had bought additional
peltier devices and fans for cooling a Steve Chambers modified
(SC-1) long exposure Philips Vesta webcam that I modified, but
I never added the cooling. When I took the Rebel apart for modification,
I studied ways to cool the CMOS imaging chip with a peltier device.
Some have tried cooling the Canon
Digital Rebel by attaching a peltier device to the metal tripod
socket at the base of the camera. This will provide some level
of cooling within the camera. The cooling effect will radiate
within the plastic camera body through its metal framework and
metal shielding. Using this method however, provides very little
direct cooling of the CMOS imaging chip.
The ideal method of cooling the
CMOS imaging chip is to have the cold finger contact the back
of the CMOS chip directly and firmly with thermal transfer paste
being used to aid in the heat transfer.
Below is a photo of the the camera
with the CMOS imaging chip exposed:
Cooling via the tripod connector
has only two metallic connections to the CMOS chip and these are
the very thin grounding straps shown in the above photo. The only
other physical connections from the CMOS imaging chip to the camera
are by three mounting screws, but these are into plastic posts.
The grounding straps are part of a thin metallic shield that lays
flush with the metallic CMOS assembly frame that surrounds the
CMOS chip. There are two copper clips on each side of the CMOS
imaging chip that are connected to the CMOS assembly frame. These
clips have very minimal contact with the CMOS chip....not good
for heat transfer. the minimal contact occurs at the very edge
of the copper clips when contact is made to hold the imaging chip
in place. Here is a sketch of the contact made:
I studied ways of directly cooling
the CMOS imaging chip without making major modifications to the
camera body. I considered the following:
Attach a 41mm by 28mm thin piece
of aluminum (cold finger) to the back of the CMOS imaging chip
using thermal transfer paste and the existing copper hold down
clips. Raise the height of the copper clips where they connect
tot he CMOS assembly frame with isolating spacers of the same
thickness as the aluminum cold finger:
The aluminum cold finger on the
back of the imaging chip needs to be extended out the camera and
to the peltier device.
I made a model of a cold finger
shape out of a piece of purple plastic to see how it would fit
in the camera:
This is how it would fit on the
CMOS imaging chip (the cold finger would be placed under the copper
With peltier cooler mounted on
The procedure would involve:
1. Removing copper hold down clips
2. Applying thermal transfer paste
on back of CMOS chip.
3. Placing Part 1 on back of chip.
4. Put isolation spacers of the
same thickness as Part 1 between the copper base and CMOS assembly
to keep existing hold down pressure the same as pre-modification.
5. Insert Part 2 through slot
in base of camera. Slot would need to have been previously drilled
out to a size needed for the cold finger runner (5mm wide). This
hole needs to be drilled through both the plastic camera body
and metal frame.
6. Attach Part 2 to peltier cold
side using nylon nuts/bolts/washers and use thermal transfer paste.
7. Place part 2 with peltier device
through camera body slot and connect the cold finger runners of
Parts 1 and 2 with small screws or nuts/bolts and use thermal
8. Use the camera's tripod socket
to bracket the peltier/ fan assembly firmly to the camera body.
Maintain clearance for battery cover so that it can fully open.
9. Wrap insulating foam tape around
base of cold plate at base of camera. This is how the camera would
appear with peltier cooler attached:
I would operate the peltier device
at full power using a variable power supply. Using the same peltier
device and power supply I have gotten good results with the peltier cooled webcam I built.
Instead of cutting a hole in the
camera body as per Method #1 above, the less obtrusive option
is to fashion a peltier cooler whose cold plate attaches to the
metal tripod connector of the camera. The cooling provided to
the CMOS imaging chip could be improved somewhat if the square
part of Part 1 in Method #1 above was mounted to the back of the
CMOS chip using the copper clips and also using the needed spacers.
Thermal paste would be used.
In addition to Method #2 above,
try to insulate the tripod connector and connect it directly to
the CMOS assembly frame. It is screwed into the frame at the bottom
of the camera with 2 small screws. These screws are in a position
that makes it difficult to loosen them, without disassembly of
the camera beyond the steps taken in Part 1. An option is to fashion
a small right angle screwdriver from a jewelers screwdriver by
bending its tip. If these screws could be loosened, an insulating
material would be placed between the connector and metal camera
frame. An "L" shaped aluminum runner could then be used
to connect the tripod connector directly to the CMOS assembly
frame using the existing CMOS assembly hold-down screw:
Before attempting a peltier cooling
method, I need to test the recently modified (filter removal)
camera for astrophotography. Nighttime temperatures here in Northeastern
PA are usually below 50 degrees most of the year so the need for
doing a peltier mod is not as great as if in warmer climates.
I recently heard from Mike Kudenov
who added peltier cooling to a 300D in a different way:
UPDATE: In April 2008, I completed the modification
of a Canon 450D (XSi) to remove its IR cut filter. I built a whole
camera cooler for the camera using a peltier device from a beverage
cooler. Modification and Peltier Cooler Construction plans can
be seen HERE.
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