I was browsing Costco's website when I came across this mini-dehumidifier (Royal Sovereign Silver Mini Dehumidifier $29.99 Item # 908759) that seems like it would be perfect for camera cabinets. I'm now living by the ocean and the humidity is quite high. I'm going to give this a go and report on how it works. See my previous blog entry on keeping cameras and lenses fungus free.
Update: Unfortunately, Costco.com was sold out of these by the time I got around to ordering one. If anyone discovers them at another store for around the same price, please let me know.
provided the camera cabinet is sealed well.
That'd be the case if this was a simple dessicant. But since you can empty this out each night, you don't have to seal it that tightly -- just as long as you can keep ahead of the humidity seeping in from the seams.
I had previously thought of making one of these myself -- a peltier dehumidifier. But I priced out the components and it'd cost me $30 in parts alone. So this is a pretty good deal.
I got a pair. The Peltier effect cooling element doesn't need a compressor like the heavy-duty dehumidifiers, but it is not silent - there is a fan sucking humid air in and pushing drier air out. Peltier junctions are also not very efficient, hence the limited dehumidification power of the unit (more like a quarter pint per day where I am). Still beats chemical dessicants, apart from the trifling detail of the wall wart and inconvenient power cords.
Another option is to use silica gel dessicant capsules that can be replenished by putting them in a microwave oven (after they have changed color). McMaster-Carr sells them in bulk.