Sometime around 2004 our house began to experience a mice problem. The usual approach of using a mousetrap was taken. However, we noticed that in some cases the mice were able to nibble on the bait without setting the trap off, despite tying the bait tightly with a string. Poison was not considered because the idea of a dead mouse corpse in an impossible to reach spot is not very appealing. The problem at hand called for a better mouse trap design. I wanted a trap that did not require the mouse to exert any force. Using a laser tripwire was an obvious solution. A laser is projected onto a light sensor. When the mouse crosses the laser and breaks the beam, the circuit will activate an actuator and trap the mouse. The trap was built from MDF wood and electronic parts bought from Jaycar.

Catch of the day!

Here are some pics of a mouse caught by the trap. So what did I do with the mouse you may wonder? Being a vegetarian I released it in a nearby wild life park. Nice and humane.

Laser activated mouse trap

The initial design for the first mouse trap is shown in Figure 1. The actual trapping mechanism is the sliding door at the front where the mouse enters. It is held up by a rod connected to a magnetic actuator that pulls the rod when energised. When the rod is pulled in, the sliding door will drop. The door is made from steel so that it is heavy enough to overcome friction and drop smoothly.

The final product is shown in Figure 2,3,4,5. Not the most elegant wiring job. It’s powered of a 12V adapter. Figure 1 shows the main entrance where the mouse enters. Figure 2 shows the back of the trap. There is a clear sliding door (peep hole) to allow the user to see the captured mouse. Figure 3 shows the metal sliding door and the circular hole where the rod connects to. I had to block the hole with a piece of wood because the mouse was able to squeeze through it! Figure 4 shows the inside of the trap after some usage. The floor is discoloured from mouse urine. Some of the wood inside was chewed on a bit as the mouse tried to escape. In hindsight, using MDF wood was not a good choice.