Ever spend all night shooting a Milky Way time-lapse only to discover the next morning that your lens got fogged up and ruined most of you shots?  No?  Just me?  Ok well just in case you’re ever in such a situation, you might find this DIY dew heater project useful.

The goal of this project is to develop a system to efficiently prevent moisture buildup on camera lenses.  The basic idea is to use electric heat to keep the lens above the dew point of the humid air surrounding it, preventing condensation (aka dew).

Power is provided by a battery pack or other DC source (12v car battery, lithium ion batteries, etc.).  A resistive heating element will be used to create a heating strip that is to be wrapped around the front element of the camera’s lens.  A simple circuit will pulse the current at a frequency set by the user to vary the amount of heat applied to the lens.

Light and compact

I wanted this device to be small and light, as I’ve already got a ton of stuff to lug around during these astro shoots.  The circuit design is simple and compact—just big enough to house the connectors and an adjustment knob.  I used surface mount components to keep things small.  This is my first foray into surface mount, and so it’s a learning experience both for design and assembly.  All the components are being soldered by hand.

Versatile

Even though this is designed for the purpose of heating my camera lenses, the controller is versatile.  It will effectively modulate any DC voltage up to 20V.  This means it could be used as a DC motor speed controller, LED dimmer, etc.   The PWM frequency may need to be adjusted to suit these applications.  This is done simply by changing the value of a capacitor.