Element-to-element interference using 3-element VL53L0X array?

[FPayn.1]

I'm using a linear array of 3ea VL53L0X sensors to orient a robot with respect to a nearby wall. The assumption is that when all three sensors return the same distance, then the robot is parallel to the wall. The sensors are mounted on a PCB with a 4cm spacing between sensors. However, my testing to date indicates that the 'equal distance' condition is achieved when the physical distances are off by about 2cm (robot about 30cm from wall).

After a lot of head-scratching, I'm beginning to wonder if maybe I'm experiencing some sort of inter-element interference, where photons emitted by one of the sensors is getting counted by the others. Is this a real issue or am I just imagining things?

TIA,

Frank

[John E KVAM]

I have a different suggestion --

During the re-flow process the sensor can be slightly altered. And this can lead to a 2cm offset error.

The first thing you have to do is put your assembly some known distance from the wall. (I always use 140mm) and do something like 50 ranges. Average these results and compare it to your 'known'. This is your offset for that chip. When you boot, place the offset in the offset register.

Then you are all set.

Read the section of the user manual on calabration. There is code - you can just call it.

Good luck.

--

I might also suggest using the VL53L4CD for this application. Code is easier. Chip is more accurate at the close distances. And the Field of view is a bit smaller.

Same footprint. same power requirements. (just a different VCSEL inside - and a few improvements.)

• john

[FPayn.1]

John,
Hmm, good point about the static offset - I have been doing this in my own code, incorporating both a 'DC' offset correction term, plus a linear correction based on measurement distance, as shown in this post (
https://www.fpaynter.com/2022/03/new-wall-following-capability-for-wall-e3/)
Regards,
Frank