Thermal imagers are awesome. Defensively, they’re a core component of perimeter defense and bug sweeping (radio transmitters and cameras tend to dissipate heat). Even the offensive set can use them for e.g keypad attacks — get to a keypad within five minutes of a legit user passing through, and you can read the code from the fading patches of heat left by their fingers.
To get around the high cost, this guy built an IR thermometer module into a flashlight and surrounded it with microprocessor-controlled color LEDs. The color shifts with the temperature of the object you’re pointing at. Unlike other DIY solutions, this means you have an arbitrarily high resolution and field of view for your “thermal camera.” You can keep the shutter of your regular camera open as long as you want and get the thermal flashlight as close as you need to the surface.
Speaking of neat DIY projects — friction-stir welding with a rotary tool: http://hackaday.com/2012/12/31/make-your-own-plastic-friction-welder/
(Friction-stir welding is good for very precise, very strong joints.)
“Thermal cameras are expensive. Even at low resolutions, it is not uncommon for a decent thermal camera to cost over $10,000. However, for only $20, you can buy an infrared thermometer that reads the average temperature over a small area. If we could turn that single area into a color and use a long exposure photography to “paint” the scene with that color, we could create something very similar to a proper thermal image.
This is not a new idea. The Public Laboratory has come out with a design for something that does this, but I have yet to see one make its way off of a breadboard. I decided to take the project to the next level and make a real, bona fide thermal flashlight. Here’s how I did it.”