PIR Activated Pest Control Trap

I've had my fair share of raccoons invading my house .... and it's always my fault for leaving the garage door open at night and allowing them to enter, climb up the shelves and find their way into the soffit area of the adjoining garage. In the past the solution was to remove a section of the aluminum soffit to allow the pest to escape when it felt hungry enough and the problem was solved. This Spring, unfortunately the latest incident involved a pregnant female who decided to deliver her litter just inside our house by penetrating through a void in the wood framing.

The pest control people were frankly incompetent and left me with a cage to trap the female on her nightly feeding excursions. But the trap was poorly maintained and I had to fiddle with it and lubricate the mechanism to allow it to trigger reliably. Raccoons are highly intelligent and this one was apparently experienced because she managed time and time again to get the bait food by walking over the pressure plate and never triggering the trap.

I figured there must be an easy way to fabricate an electronic trigger. Arduino comes instantly to mind but I wanted something a little more robust and more self contained than a breadboard. Complicating things was the pandemic lockdown in my city limiting my access to my local electronics store. I was able to order online and arrange a curbside pickup but as a tinkerer you know how often ideas occur when one is simply browsing aisle upon aisle of components.

I was fortunate to come across an old Philmore PIR (passive infrared) motion detection kit that ran on 12VDC as well as a 12VDC solenoid rated at 20N of pull on the electronic store's website. It took only about an hour to solder all the components in the kit and it has a flyback diode to prevent inductive kickback from the solenoid. I tried to tie the solenoid directly to the board outputs which were showing 12 V but it would never activate I'm sure there is an easy and good explanation for this but unfortunately my electronics knowledge is very peripheral. I figured I needed a relay in between the board and solenoid and found some very nice24V relays on an old garage door opener motherboard I had lying around.

I found the relay would not actuate reliably at 12 VDC but by decreasing the distance between the armature contact and the activating contact by simplying bending the upper contact support, I could get it to work and activate the solenoid. (Image 1)

Even with 20N of pull, the solenoid was not strong enough to trigger the trap unless I set it to a position where is was nearly able to slip and spontaneously set itself off. (Image 2)

Check out the video!

I surrounded the sensor region with cardboard around the cage to prevent false triggering of the PIR sensor.

It can be most conveniently run off a 12VDC battery in remote situations away from an electrical outlet.