Canon 5DH now 30C+ deg C Below Ambient

[avandonk]

I have put a much better heatsink on the Peltier fridge. The cold finger going in to the fridge has also been better insulated. The fan is running way below full speed and it makes no difference to the lowest temperature obtained.

I am easily getting 23C below ambient.It is a bit difficult to measure it accurately as ambient keeps falling. The best I could get before was about 15c.

Pics below.

Bert

[Lester]

Excellent Bert.

[h0ughy]

fantastic work Bert, looks like a set of extractors on a v8!!!

[Bassnut]

Thats a cool project, well done. How do you stop frosting?. (I get hammered by Houghy on this on my project, now its your turn ;-)

[netwolf]

Bert, so when are you going into mass production?
This would be a very neat add-on for all the DSLR imagers.

Regards
Fahim

[avandonk]

h0ughy it is a heatpipe CPU cooler. It easily handles the heat load of the Peltier or TEC. In fact the Cu plate in contact with the TEC is barely (less than finger temp.) warm. The original Al heatsink was very hot (burnies to finger!) near the TEC.

Bassnut I have no condensation problems as the heat exchanger inside the fridge has a fan blowing on to the camera. The heat exchanger is the coldest object inside the fridge and any condensation occurs there. In fact I have very quickly removed the fridge when it was -12C inside and all metal objects outside were dripping with condensation and the outside of the 5DH was bone dry.

This is fridge mark 2 or 3. I will next modify the power supply to keep the fridge at a constant temperature as TEC's don't like being switched on and off continuously such as a simple thermostat would produce. Temperature controlled PWM would be far better and have far less hysteresis or sawtoothing.. This of course means darks will actually be at the temperature of the lights.

Netwolf I have no intention of making them en masse. I will make all details available though.

Bert

[h0ughy]

;) have ha this dscussion with Bert:whistle:

[avandonk]

To those that are interested have now stacked two Peltiers and I am getting a 30C+ drop in temperature! It is not all that simple as the second Peltier has to cope with the heat that is generated as well as the heat pumped by the first. So as usual we have the law of diminishing returns rearing its ugly head. I used a Peltier that has twice the heat pumping capacity of the first so they could both be electrically connected in parallel. This keeps the DC power requirements simple.

Putting polystyrene expanding foam around all the cool bits helps also.

Bert

[Lester]

Wow, Bert, where is this going to end 30 degrees below ambient.

Ground breaking stuff.

[avandonk]

Even though it was cloudy, set up the fridge yesterday to test it on the camera. The fridge easily gets 30 deg C + below ambient when empty.

Ambient yesterday started off at 26C the fridge got down to 3C while the 5DH was continuously taking images.

I took 4min images at an ISO of 1600 with the ICNR OFF and the dust cap on the 100ED.. Here is a movie of 44 frames where each frame is a 300x300 crop of the center of each frame. Starting at 26C down to 3C.

http://members.optusnet.com.au/~trlee8/002.gif


The camera will lag behind the fridge temperature but after 3 hours equilibrium should have been reached. I was hoping to run until the predicted low overnight of 12C which would have produced a fridge temp of about -10C or more. Rain stopped play!

Bert

[Karls48]

Hi Bert, that is dramatic improvement. I’m using Peltier to cool DSI Pro but I get only 13 deg below ambient. It’s because I’m using too small heatsink on hot side. But even that small temperature drop helps to reduce hot pixels. To regulate temperature I’m using Temperature Controller kit from Oatley Electronics. Works fine but it needs heatsink on output FET.

[avandonk]

Karl what size Peltier are you using? Size in mm and current. The newer heatpipe copper heatsinks are far better than plain vanilla aluminium. Here is one that would fit nicely on the back of a DSI and would work well without a fan.

The controller you mentioned sounds interesting. I need to control about seven or more amps to get a constant temperature in the fridge.

Here
http://www.pccasegear.com.au/prod5602.htm

Bert

[Karls48]

I’m using 4A 40 x 40mm Peltier. I butcher DSI heatsink fins so the Peltier sits flat on the camera body. Hot heatsink is from some old CPU with original fan. I cut two notches on remaining camera heatsing fins so it can be clipped on. The camera body is insulated by black foam, glued on by contact cement. I know it could achieve lower temperature with bigger heatsink, but the camera is heavy and bulky as it is.
The controller comes with tiny thermistor to sense temperature. I drilled small hole in the heatsink, fill it with heatsink compound and epoxy thermistor in it. Output FET is MTP3055 rated at 12A. It really needs heatsink and you have to fashion one yourself, as there is no provision on PCB to mount one. For your application I would change this FET for one that can handle bigger current. There is one mistake in the assembly instructions concerning jumper link that configures PCB for cooling or heating. If you going to build it, let me know, I will look where that link is supposed to go.

[avandonk]

Thanks Karl for the controller info. It is greatly appreciated. I have more experiments to do to get the best fridge before I even start to control the temperature.

Bert