This ultra-cute tiny LiDAR rangefinder project by [gokux] can be thought of as a love letter to the incredible resources and components hobbyists and hackers of all types have access to nowadays. In fact, it all stemmed from coming across a miniscule half-inch 64×32 OLED display module that was simply too slick to pass up.

To use it, one simply powers it on and the display will read out the distance in millimeters. The VL53L0X time-of-flight sensor inside works by sending out a laser pulse and measuring how long it takes for the pulse to bounce back. We hope you’re curious about what such a sensor looks like on the inside, because here’s a nifty teardown of these fantastic devices. The device can technically measure distances of up to 2 m, but [gokux] says accuracy drops off after 1 m.

The main components besides the OLED display and VL53L0X sensor are an ESP32-C3 board (which handily integrates battery charging circuitry), 3D-printed enclosure, tiny rechargeable battery, and power switch. The whole thing is under one cubic inch. Not bad, and it even makes a passable keychain. Parts list, code, and 3D model files, including STEP format, are all available if you’d like to spend an afternoon making your own.

Wait a second, read that title again. This isn’t a throwback 3D printing project at all. That’s “RepTrap” as in reptile trap, and it’s a pretty clever way to study our cold-blooded friends in their natural habitat.

Now, game cameras — or trail cameras, if you’re less interested in eating what you see — are pretty much reduced to practice. For not that much money you can pick up one of these battery-powered devices, strap it to a tree, and have it automatically snap high-quality pictures of whatever wildlife happens to wander past. But nearly all of the commercially available game cameras have pyroelectric infrared sensors, which trigger on the temperature difference between a warm-blooded animal and the ambient temperature of the background. But what to do when you’re more interested in cold-blooded critters?

Enter [Mirko], who stumbled upon this problem while working with a conservation group in Peru. The group wanted to study snakes, insects, and other ectothermic animals, which are traditionally studied by trapping with pitfalls and other invasive techniques. Unable to rely on PIR, [Mirko] rigged up what amounts to a battery-powered light curtain using a VL53L4CD laser time-of-flight sensor. Mounted above the likely path of an animal, the sensor monitors the height of everything in its field of view. When an animal comes along, cold-blooded or otherwise, RepTrap triggers a remote camera and snaps a picture. Based on the brief video below, it’s pretty sensitive, too.

[Mirko] started out this project using an RP2040 but switched to an ESP32 to take advantage of Bluetooth camera triggering. The need for weatherproofing was also a big driver for the build; [Mirko] is shooting for an IP68 rating, which led to his interesting use of a Hall sensor and external magnet as a power switch.