User avatar
HermannSW
Posts: 1601
Joined: Fri Jul 22, 2016 9:09 pm
Location: Eberbach, Germany
Contact: Website Twitter YouTube

Mouse trap: from 0 to 72km/h in 8ms(!)

Sun Feb 24, 2019 7:21 pm

Two days ago I posted 1007 fps mouse trap closing videos with different very short shutter times resulting in very clear frames although the fast speed of closing mouse trap bar:
https://www.raspberrypi.org/forums/view ... 8#p1433278

Today I looked at the video again and arranged the frames of interest. In order to avoid display problems on smaller screens here is the .html link, as well as a screen capture (640x150_s tool captures 320x75 frames covering 640x150 FoV):
https://stamm-wilbrandt.de/en/forum/72k ... rames.html
Image


In frames -2, -1 and 0 the bar has not been triggered. In frames 1-5 you can best see the progress by following the upwards going part of the trip, in frames 6-8 you can easily see the progress by the mouse trap bar itself. In frame 9 the bar moves further, with touch down on lower side in frame 10, and touch down of middle in frame 11.

The bar moves on 4cm radius. The important point is that the bar is in middle at bottom of view in frame 7, while in frame 8 it is 2cm more right (just the half ofthe radius). This allows to determine the velocity at that point in time:

Code: Select all

v = s/t = 0.02m / 0.001s = 20m/s  or 72km/h(!)
Further this speed happens at frame 8 of bar movement in 1007fps video, that is after 0.008s. This allows to determine the acceleration of the mouse trap bar:

Code: Select all

a = v/t = 20m/s / 0.008s = 2500m/s²
That is more than 250 times standard gravity (humans get killed by very short acceleration of 50g already).

Summary:
Impressive numbers, 72km/h speed for mouse trap bar after only 8ms because of >250g acceleration.
Thanks to v2 camera 1007fps videos captured with around 19.5µs(!) shutter time we can get very sharp images for measuring high speeds!
Last edited by HermannSW on Mon Feb 25, 2019 7:15 am, edited 2 times in total.
⇨https://stamm-wilbrandt.de/en/Raspberry_camera.html

https://github.com/Hermann-SW/Raspberry_v1_camera_global_external_shutter
https://stamm-wilbrandt.de/github_repo_i420toh264
https://github.com/Hermann-SW/fork-raspiraw
https://twitter.com/HermannSW

Andyroo

Re: Mouse trap: from 0 to 72km/h in 8ms(!)

Sun Feb 24, 2019 8:38 pm

Wow - thanks for sharing that. I'm amazed by the results you have got.

So how the heck did the baby mouse we caught last year manage to get its head out in time and get trapped by its leg? And yes - we did let it go in the fields near us :D

Return to “Camera board”