Instructables

Step 2: Mouse Trap Results

Picture of Mouse Trap Results
The plot shows the signals captured by the oscilloscope, representing the release and close of trap. Three sets of data were collected from the mousetrap, and the waveforms captured were all similar to that shown. The timing results between runs were fairly consistent.

The timing from release to first closure was always about 12 milliseconds. I performed the same measurements on both of the traps that were included in the package, and the results were again fairly consistent.

Note the “bouncing” visible as the bar slams down on the front contact. Anyone who has dealt with interfacing mechanical switches to digital inputs will be familiar with the need to “debounce” the inputs. Mechanical contacts generally don’t just make a solid clean connection when closed. Instead, the switch contacts actually open and close several times before settling on a stable state. Notice that the timing between the initial closing and the second closing is fairly large, about 4 milliseconds. The subsequent closings are more closely spaced, until the bar finally comes to rest and switch stays closed.

I don’t have a high speed camera, but there are high speed videos of mouse traps on YouTube. When I viewed some of them, you could clearly see the bar bounce back up from the wooden base about half an inch after the initial contact. This agrees with the bouncing seen on the graph.

To put the 12 millisecond close time into perspective, one cycle of 60 Hz power is 16.7 milliseconds. So the trap slams shut in about ¾ of the time it takes the voltage on your AC outlet to make a complete cycle. I looked up how fast a humming bird’s wings move, and the general range stated in various sources was between 50 and 80 beats per second. So, the trap will slam shut about as fast as a single flapping of a hummingbird’s wing.

The 12 milliseconds represents the time for the bar to impact the wooden base. If a mouse were present, eating food from the bait holder, then the bar would not have to even travel that far to hit the mouse. So, if you are a mouse eating from a trap and you accidentally trip it, you actually have less than 12 milliseconds to back out and escape. I’m pretty sure that no mouse can move that quickly.

You could say that the bar of a mousetrap literally travels at “break neck” speed!
Nice done :)