Keeping the CCD-Chip free from frost

The biggest problem with the Audine camera was to prevent the CCD from freezing due to water vapour in the air when the cooling is started. Just sealing the housing was not enough, there are still several places where the camera is not airtight and there is a lot of unused space inside the camera. You could fill this emty space with foam to reduce air mass inside the camera, less air = less water vapour. I also put (blue) rubber gaskets between the body parts and silicone aquariumkit around the connectors. Silica Gel is used to keep all kinds of equipment dry and I obtained some with a color marker. On the picture you can see the two stages. Blue is dry and pinkish is saturated. After testing with a small bag filled with Silica Gel inside the camera, I guessed this was the way to go. But changing the Silica required the camera to be opened and that was very bothersome. So I bought a Silica Gel drying unit for electronics from Farnell . It is Farnell Item Nr. 561459 "Dessicator" . It's container has a window for checking the dessicant and at the bottom is a kind of filter to stop dessicant dust from entering the camera. I made it a bit shorter and put my own Silica Gel inside. In the side of the Audine housing I made some 4-5 mm holes and glued the fastening nut onto it. I put a flat rubber gasket between the container and the Audine housing and screwed the container in the nut, a teflon ring might be even better. Now I can see when I have to change the Silica, and it is a job that takes about 2 minutes without opening the camera. After a week or so the Silica turns pink again so it needs changing. But it is an easy job to do and the reward is that the CCD never freezes, even when it's -10 degrees Centigrade outside. The Silica gel is regenerated by putting it in an oven at 100 degrees Centigrade. Putting it in the microwave for a few minutes at low power will do the trick as well. I did not test if the material of the container is microwave resistant so I take the dessicant out (the "grid" end of the container comes off) and put it on a dish. I hope the pictures below give you an idea of how I did it.