Can multiple VL53L1X be operated in parallel?

[LDi C.1]

Sensors are close to each other (let's say, 30cm). The range is the medium-long one. Their FOV may overlap in production. I'm using ULD.

Does this means that I have to VL53L1X_StartRanging and then wait for its result before calling VL53L1X_StartRanging of another sensor?

Thank you

[John E KVAM]

The good news is you don't have to worry about it. Each sensor sees the other as an ambient light source and accounts for it. You can even point them at each other.

So start one ranging, then start the other ranging, wait for the first one to finish, read the result, and by the time you've done that, the second one should be finished.

If you get inconsistent answers that don't give you the accuracy you want, add more time to the timing budget.

• john

[LDi C.1]

That's amazing! I'm sure there is some IP rights here, but I try anyway. How do you achieve this? Emitting different codes for each sensor? Like a sort of UID sent with the modulated pulse that cannot overlap with other UIDs?

I have a second question. This application I'm working on is indoor. But what about using such technology outdoor. Specifically, would it be feasible to remove old-school devices like these (magnetic loop detectors for vehicles):

https://www.feig.de/fileadmin/user_upload/Downloads/News/2014-03-10_VEK_MNE2_and_Software_E.pdf

It should be able to work on sunny day, during raining (heavy raining) and during snow. What happens if snow accumulates on top of the sensor cover?

I read in the datsheet that the distance detected in case of 200kps/SPAD is max around 70 cm. Is there any technology able to achieve more?

The system needs to detect the distance, not just the presence, to understand if a vehicle or something else stands in front of the sensors. i can use an array of sensors but the target may be even 2 meters away.

Thank you!

Luca

[John E KVAM]

Luca -

It's not that fancy, we dither the timing so the other sensor will never line up with each other. Not only fixes this problem but solves a pretty tricky EMI problem.

But let's not get too crazy here. We are still talking about a few dollar part. It's not going to change the world that much.

It's an indoor part. We use an eye-safe laser. It's no brighter than an indicator LED. Has to be - the light will enter your eye, and you won't know to blink.

So you can imagine what happens in bright sunlight. The light just gets lost in a sea of light.

A second sensor isn't nearly as bright as sunlight, so we can handle that.

Oddly the sensor sees right through snow. Doesn't see it much at all. A guy in Canada wanted to know. We spent hours in the freezing weather, knee deep in snow.

Laser eye-safety depend on brightness over time. So you can have a very bright pulse of light if you have a very short duration.

So a rotating laser, that pulses very quickly can be a lot brighter. But the electronics required to drive that much power that quickly are not cheap.

And if you increase the frequency of light, it will no longer penetrate the eye. But the detection technology changes at higher frequency of light.

Autodriving cars are 'driving' this market, but those lasers systems are still pretty expensive. Still in the thousands of dollars.

= john