The first iteration of this trap involved using a Passive InfraRed (PIR) Sensor to detect motion and determine when an animal was in the trap. This approach worked great...In the garage and at night. When taking this setup outside into the Texas sunshine and heat, it flagged a lot of false positives. I spent a lot of time toying with the sensitivity, but ultimately I scrapped the PIR sensor. At the end of the day, if it's 98 degrees outside and an animal with a 99 degree body temperature enters the trap, PIR won't be a reliable detector.

Rev2 involved an active Infrared LED emitting a signal and relying on a 35kHz infrared receiver to detect whether or not there was something in the trap to bounce the signal back. This worked relatively well but I never got it solid to the point where I was confident that I could reliably detect motion.

At the time I'm putting this on Hackaday.io I'm working on an ultrasonic-transducer version to detect whether or not there's something inside the trap. I'll bounce a signal from the roof of the trap to the floor, and based on the travel time of the acoustic signal we can determine if there's something in between the floor and the ceiling.