ThermoPen, the Infrared Thermometer Pen

Measuring temperature at a distance via an infrared sensor is nothing new. If you buy one from XYZ online retailer, you’ll probably get something that more or less works, but that comes in a fairly large housing. Additionally, you may not know much about the actual sensing unit, or how closely aligned it is with the aiming laser. Another option would be to design and build your own, like Xavier’s infrared thermometer pen.

As shown in the video below, the aptly named ThermoPen isn’t that much bigger than a standard writing unit, perhaps comparable to a good-sized highlighter. On the side, temperature stats are displayed on a small OLED screen, and the aiming laser diode is attached adjacent to the Melexis MLX0614 IR thermometer for maximum positioning accuracy.

The 3D-printed case went through roughly a half-dozen iterations before settling on a final design, which really comes through in the sleek appearance of the unit. In fact, it’s a bit reminiscent of a TS100 portable soldering iron, sans the actual metal tip.

Inside the ThermoPen, an ATmega328P microcontroller acts as the brains of the operation on a small PCB that houses over 50 parts. Li-ion battery charging is included as part of the device, and thanks to a capacitor setup it actually works for a few seconds after being turned off. This could be rather useful when you didn’t quite remember the unit's output before releasing the button. If you’d like to build your own, project files are available on GitHub.