Sensor suggestion?

Community Projects
1

I need your suggestions on choosing appropriate sensor for my project.

I have some rolling tyres and I need to measure time (and speed) of them, while rolling, by sensors. It could be easily done by putting a laser sensor on one side and a LDR (light dependent resistor) on the other side and read and measure the time in which received signal is being cut by rolling tyre. But, it has to be on one side only, so on the other side I don’t want to put LDR.

Considering application requirement as below, what are your recommendations?

Is it possible to use reflectors on the other side?

Do I have to use rangefinder sensors?

Covering distance: 20cm-3m

resolution (at beam spot): 0.1mm

short time-of-flight

http://fs5.directupload.net/images/160520/hxjr28tg.png

Thanks

2

Why do you think you need a rangefinder sensor? And why is “time of flight” important? Ranging in the suggested direction (perpendicular to tire motion) is not going to give you any information about speed of the tire passing in front.

I’d say a reflector or properly aimed mirror should do the job while having the emitter and sensor on the same side. If you want speed information then you could use the time duration of (laser-)light blockage, but then you also need to know the size of the wheel. (Wheel diameter divided by duration of light blockage is rolling speed) And the wheel should not bounce up an down so it always has the same width at the level of the light beam. Or the lightbeam could shine through holes in the hub, then you need to adjust the beam to a level that prevents that and use an appropriate ‘apparent’ wheel width to compute real speed.

3

Thanks Valen for your reply.

You’re right.

by using Rangefinder sensor, before, I didn’t want to measure speed, but to detect tyre is passing.

But using a reflector via a laser sensor seems a lot easier to do it. Do you have any suggestion on this part (laser sensor + reflector)?