A dew heater can be a difficult thing to do if you are not sure how to build one, however it doesn't have to be that hard.
We now have a really simple, pre-assembled dew heater available, with an included USB dew strap that fits most camera lenses. This fully assembled and tested dew heater, in a 3d printed case (not pictured) is $100 plus delivery.
Very simple operation:
Plug the dew heater into a permanent USB power source (permanent as in one that doesn't turn off with low loads), plug in the heat strap to the other end, and the heater is ready to go.
If the controller detects that the dew point is less than 2 degrees below the current temperature, it will switch on the heater strap, protecting your lens from condensation.
If the controller detects that the dew point is more than 2 degrees below the current temperature, it will switch the heater off, saving battery levels.
Email us at firstname.lastname@example.org for more information.