OpenTrap Smart Animal Trap

The Ultrasonic transducer arrangement is working quite nicely. I had to use some rubber pads underneath the transducers to minimize direct coupling when firing the transmitter, but after doing that it seems to be happy.

The next challenge is getting rid of the servo. The original build requires modifying the trap to allow connection of a hobby servo, then the servo is driven by the Trap Box to close the trap. This works reasonably well, but it's got several drawbacks:

- It requires modifying the Trap by cutting the 'pull rod' to be able to connect the servo to it.

- It requires over-voltaging the servo to get enough force to consistently shut the trap (7.2V battery on a 6V servo). I've not had any issues in hundreds of cycles on this servo, but it would be better not to run outside the manufacturer's recommendations.

- Adjusting the connection between the servo and the pull rod is somewhat subjective and it should be more fool-proof.

-Because the pull rod is connected to the servo, it's necessary to disconnect/cut a connection in order to remove the servo (assuming the user wants to remove all electronics before taking the cat off to the vet, this is a hassle for the user and unnecessary extra stress for the animal).

What I plan to do here is use a solenoid to actuate the trap. This is a good option since the solenoid is cheaper and simpler than the servo. The problem is that I've not had much luck sourcing a 6V solenoid that has enough force to consistently close the trap. I have a 12V solenoid that works great, but as of now the system works on a 7.2V battery, and when we start looking at 12V batteries the price starts jumping up fast! I'm currently working on a simple boost converter to step my 7.2V up to 12V+ for long enough to hit the solenoid.

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.