Vl53L1X Velocity Measurement

[GEl-S.1]

Apologies if this is a dumb question or fairly simple. 

I plan to use the VL53L1X to measure the velocity of an object for a university project and was wondering if there is a way to extract the velocity of the object from the distance/range measurements?

Would the only way to do that be to calculate the time in between measurements and use the difference in distance to get velocity? Or is there a way I could use the speed of light or the time taken between measurements to extract velocity?

[John E KVAM]

I'm not sure this will work very well.

I tell everyone that we shoot out a photon and start the stopwatch. When the photon comes back we stop the timer and calculate the distance based by dividing the time by two and multiplying by the speed of light.

The basics are there, but it's far more complex than that. We can't actually measure down to the picosecond, so we use a LOT of photon blasts and do a lot of math to get the position of the object. A really good measurement uses 20 million photon detects to get an accurate answer, for instance. But we need at least a half million or so.

It takes on the order of a dozen milliseconds to get a measurement. And in that time, your target will have moved quite a bit.

If you have a slow vehicle - like a robotic vacuum, this number of milliseconds to get a measurement is not an issue, but if it were a drone it would be another matter entirely.

It is neither a simple nor dumb question. And your idea would have worked just fine had not the physics of light and the limitations of a couple dollar sensor come into play.

I'm actually glad you asked.

[RGupp]

Further to your reply i offer a suggestion to improve the sample time problem. That is, if you could use multiple sensors and stagger the measurement timing could you effectively increase the frequency of distance measurements. There are other posts on this "Proximity Sensor" group that discuss the use of multiple sensors, which you would have to handle if you had multiple sensors. I tried to depict the sequencing below for three sensors tagging the distance measurement as M

___[------M]_[-----M]__

____[--------M]_[-----M]__

______[------- M]_[-----M]__

I'm fairly new to the sensor myself so take this suggestion with a grain of salt but at least theoretically at least, this may help?

regards

ralph

[John E KVAM]

You hit on an absolutely do-able idea. That will work. if you start them staggered like that, they will stay in lockstep.