RepTrap watches over our cold-blooded friends

Wait a minute, 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 limited to practice. For not that much money, you can purchase one of these battery-operated devices, strap it to a tree, and have it automatically take high-quality photos of whatever wildlife happens to wander by. But almost all commercially available gaming cameras have pyroelectric infrared sensors, which activate the temperature difference between a warm-blooded animal and the ambient temperature of the background. But what should you do if you are more interested in cold-blooded creatures?

Enter (Mirko), who encountered 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 using pitfall traps and other invasive techniques. Unable to rely on PIR, (Mirko) set up a battery-powered light curtain using a VL53L4CD laser time-of-flight sensor. The sensor is mounted above an animal’s likely path and monitors the height of everything in its field of view. When an animal passes by, cold-blooded or otherwise, RepTrap activates a remote camera and takes a photo. Based on the short video below, it’s also quite sensitive.

(Mirko) started this project with an RP2040, but switched to an ESP32 to take advantage of the Bluetooth camera triggering. The need for weather resistance was also a major driver for construction; (Mirko) is aiming for an IP68 rating, which led to his interesting use of a Hall sensor and external magnet as an on/off switch.