[PD] [OT] Using a webcam to measure a wheel's rotation speed

Thomas Grill gr at grrrr.org
Thu Sep 2 18:52:32 CEST 2010


Hi Matteo,
can't you mark one of the spokes or the wheel and setup the camera in a distance so that a blob tracker can cope with it?
Then, it's fairly easy to measure something like the zero-crossing rate along one dimension x or y.
gr~~~

Am 02.09.2010 um 17:54 schrieb Matteo Sisti Sette:

> Hi,
> 
> I need to measure the rotation speed of a spoked wheel.
> 
> As an alternative to a suitable sensor + arduino, I was considering using a webcam placed very close to the wheel and counting the frequency at which the spokes pass in front of the webcam.
> 
> Has any of you tried anything similar? Do you have any suggestions?
> 
> 
> My naïf idea is that if a (natural or artificial) source of light is placed in front of the webcam, when the spoke passes in front of it, it will reduce considerably the brightness of the whole frame or of a big portion of it.
> 
> I'm looking for something simple: if this eventually leads to a complicated artificial vision task, or if a good calibration is difficult to achieve, then I would rather go for a tachometer and an arduino...
> 
> 
> Thanks in advance
> m.
> 
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