YouTube hacker MN Maker was working on a circuit when he noticed a component getting extremely hot. He wanted to know the temperature, but as he didn’t have an IR thermometer he decided to create one himself!
The resulting build is similar what you may have seen for sale or in use, with a handle that holds the battery, a small display, and a “nozzle” situated at 90 degrees. This part of the assembly emits a laser for aiming, and uses MLX90614 non-contact IR sensor to do the actual measurement work. The device is controlled by an Arduino Nano, and temperature info is conveniently displayed in both Celsius and Fahrenheit on a small OLED screen.
User interface consists of an on/off switch, along with a momentary pushbutton. The thermometer scans the temperature at all times when switched on, but only turns on the aiming laser and displays results on the screen when the button-trigger is pushed.
As with nearly any project, MN Maker underestimated the amount of room that wiring would take, but was eventually able to squeeze everything into the housing and secure it with hot glue. Arduino code is available on the project write-up, and STLs can be found on Thingiverse if you’d like to make your own!