What can cause a location to trigger error 2 constantly ?

GJour.1 · ‎2020-07-03

I am using VL53L1X for indoor presence detection, mounted on the ceiling and looking at the floor, and it is doing great. However recently I tried it in a new location, and I have nothing but errors. I have several sensors there, and all of them are stuck with error type 2, and a sig rate at 0 for 90% of their measurements (using different ROI and different time budget. Usually I use 16x16 and 100ms and it is doing great, but here it seems nothing goes).

It is not in direct sunlight, but one wall is open to the exterior, so the ambient light is partly sun, partly artificial light from neon light bulb. However the ambient rate doesn't seem to pike higher than I use to see in other cases.

The floor is a bit dirty, its paint is dark but reflects light a lot. However errors are the same when an object is present, so the floor may not be the cause.

Is it possible that an unknown source of 940nm could mess this up ? An IR CCTV for instance ?

John E KVAM · ‎2020-07-03

It's not an unknown source of 940nm, it's sunlight. Set up your experiment in the late evening or early morning and it will work. Then check it every half hour as the sun comes up. At some point it will stop working. And it's the amount of ambient light that is cutting down the range.

We collect the Ambient light, and you can read it from the chip after each range. You will undoubtedly see it go up.

WE can range 4M with a big target and no ambient light. But the range goes way down with sunlight. And Sunlight hitting the floor and dispersing everywhere is the issue.

As the day gets brighter, your eyes adjust. So your eyes are not a very good way to measure brightness.

So Check the ambient, it will tell you what is going on.

john

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John E KVAM · ‎2020-07-03

It's not an unknown source of 940nm, it's sunlight. Set up your experiment in the late evening or early morning and it will work. Then check it every half hour as the sun comes up. At some point it will stop working. And it's the amount of ambient light that is cutting down the range.

We collect the Ambient light, and you can read it from the chip after each range. You will undoubtedly see it go up.

WE can range 4M with a big target and no ambient light. But the range goes way down with sunlight. And Sunlight hitting the floor and dispersing everywhere is the issue.

As the day gets brighter, your eyes adjust. So your eyes are not a very good way to measure brightness.

So Check the ambient, it will tell you what is going on.

john

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GJour.1 · ‎2020-07-06

Thank you very much John for your precise and quick answer.

The sun was indeed my first guess ; However during the night I still have low signal, which never happened anywhere else. I am used to efficient measurement everywhere I try, even in my office with strong ambiant light coming out of the window. The signal may not be very strong but there is always some.

In this specific location, it is very bad, even during the night.

Are you positive that no other IR source could interfere ?

I will double check ambient light on different time, and maybe do different measurement at various range to evaluate more accurately.

Thank you for your time,

Gauthier

John E KVAM · ‎2020-07-06

Could it be that it's the floor that is the difference? In that code we need to 'see' the floor. But if your floor in this new location is not as reflective or is farther away, it could be being missed. Try this. Put a few sheets of white paper on the floor under the sensor. Does that fix your issue?

The only sources of 940nm ambient are the Sun, Halogen lights, a very few really odd florescent lights and really cheap birthday candles.

I just cannot think of anything else.

john

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GJour.1 · ‎2020-11-30

In the end it seems that indeed the floor was the major cause of errors. I don't know exactly why in this particular location, maybe it was made of a particular material. We solved the problem with a reflective white sticker on the floor and it now works like a charm.

Thanks a lot !