Hi guys, well as some of you may know I have been playing around with the cooled camera concept.
I have taken on a different path to Bert, (avondonk) however he did give me some support in the powering of this thing.
Tonight I did a bench test of the cooler, it was exactly 32 degrees in the shed, so i hooked it up to see what it could do out in the open air of 32 degrees.
Well to say the least, i was pretty happy, in 15 minutes it went from 32 degrees, to 16 degrees, and it was not even enclosed in the chamber that i will house it.
Anyway this is my starting point, and as the experiment grows I will keep you all informed.
I noticed the amount of frost on the cold plate. I don't know how you propose to attach your camera to the Peltier, but it would be a good idea to avoid the frost buildup, as it adds significantly to the thermal load. Also, 15 mins seems a long time for the cooling to happen - in my experience 15 seconds would be closer to the mark!
You do mention that you will be enclosing it in a chamber. What I have done with a Peltier-cooled photodetector that I have been involved with, is to hermetically enclose the Peltier/detector unit with an activated desiccant sachet, or a molecular sieve (http://en.wikipedia.org/wiki/Molecular_sieve), to remove the water vapour. Additionally, if you have access to dry Nitrogen, then flush the chamber with this first before sealing off. You can easily gain up to 5-10 (or more) degrees doing this - even without the N2 flush.
You mention that the cold face was at 16C and the ambient was 32C - it would be a good idea the get the temperature of the heatsink at the hot side of the Peltier. This will allow you to determine the temperature differential of the Peltier unit. The dT should be at least 40 degrees or more (50-60C, depending on the Peltier type) when the optimum power is applied.
You may also benefit from a shroud around part of the heatsink, on the fin side, to concentrate the air flow over the fins.
I experimented with peltier cooling some time ago, all I did was get a couple of peltier devices from Jaycar and stack them onto a fan cooled heatsink from an old PC.
The cold face got down to -25C with a little aluminium heatsink attached to simulate a thermal load from, say, a big ccd
Frosting/dew will be an issue.
I notice you have frost all over the cold face but the thermometer is reading +16C? Should be less than 0C to get frost... I see the thermometer's sensor is bolted to the cold face, but perhaps the actual thermal sensor is in the body rather than the mounting ring... and it's not in contact with the cold face. See if you can get the sensor body right up against the cold face
Quick question, I am guessing you externally powering the camera?
USB control for the camera would be very useful in this configuration, as it would allow you to seal the box up and not have to open it to change settings.
Also, how are you preventing condensation on the imaging window? Are you sealing the front of the camera to a reducer/flattener? If so, you could put a small dew heater on the reducer to prevent condensation on the front optics.
Also, how are you preventing condensation on the imaging window? Are you sealing the front of the camera to a reducer/flattener? If so, you could put a small dew heater on the reducer to prevent condensation on the front optics.
To answer this, the imaging window will not fog up, and i know this because i used a fridge like this in the winter time.
The cmos will stay about 10C while the inside of the box can be about -12.
At the moment i am modding my 40D to directly cool the cmos with an peltier and i can get the cmos as cold as -14C when working, or about 25C below ambient, have to make it better regulated to keep it at 5C.
I bought a large camping fridge for the trip to Bathurst recently.
Along the way, I got a goodie.
It was drinkcan cooler (Called a "drinkmaster" also called "myfridge" in the US. Made by WAECO).
I have been reading what you guys have been doing and it came to me.
By using the free goodie for a camera cooler. Not sure what the wife will think (of destroying it for scope purposes), but it's a thought.
After the humid conditions in the past few days, it started to freeze up a bit. Haha.
But after seeing, your "frosty" pic Leon, it made me write this post!
Brett, i too bought a small cooler from Dick Smith and pulled it apart and will be using the switches and cooler unit for this experiment, but my container for the camera is going to be somewhat smaller than the cooler I pulled apart.
It will also have a small computer fan installed to circulate the cold air and help with condensation.
Just playing around at the moment, this may not even work.
