How to use the VL53L5CX with indirect sunlight

[jdumaresq]

HI,

We have an application where the VL53L5CX is used near a door that are indirectly exposed to sunlight.

I try to be able to do some measurement around 1m. Indoor, the sensor is working good. If I put the sensor near an exterior door, I see some of the cell get values, but most of them have a statuses of 255 or 12.

What's is the maximum ambient light value to have a working sensor ? (the ambient value from the sensor reading).

How we should interpret the SignalPerSpad ?

The sensor is facing face down from the top of the door on the inside side. So the sensor is not directly exposed on the sun.

Is there config values that we can change to add a bit more sunlight noise ?

[John E KVAM]

One's eye is a terrible tool for measuring brightness. The Iris closes down and and it's very hard to tell a really bright day from a bright one. Generally one gets a clue as to the sun's brightness by lack of clouds or temperature.

The sensor returns a measure of ambient light. And if this ambient gets too high, the sensor cannot find the returning signal because the sensor is saturated.

Generally we could overcome some of this by turning up the laser power. But that would affect the eye-safety. So it's not an option.

When you find a situation where the zone returns 255, look at the ambient measure. That is your max.

I've found the sensor works best if the sun is 90 degrees to both the sensor and the target.

I've also found that 4x4 works better than 8x8 in high sunlight.

good luck,

• john

[jdumaresq]

Hi,

Thanx for the quick answer,

I also found that the halogen lamp create similar effect of the sun. I place the sensor at 950mm of a wall and I light up my 500w halogen lamp and point the lamp to the wall.

here a screen shot off 1 sample before lights up the halogen lamp

After I light up the lamp

R is ranging

S is status

A is ambiant

L is signal per pads.

How should I interpret those number ?

Are there any other information should I show/take care of ?

[John E KVAM]

Thankfully halogen lights are rarely used anymore. They generate a lot more unusable energy than usable light. And your plots show the effect perfectly.

Looking at your data, I'd say anytime you get over 1200 KiloCounts per SPAD per second, you are likely to get a 255 error - 'couldn't range due to excessive ambient'.

But there was one valid range with 1900 counts so it's possible that your target was especially bright in that one zone.

Consider the signal to noise or (L to A) ratio in this plot. You have a good strong signal, but then you have an amazing amount of ambient.

How well you can range this light depends on your target - which is why it's so hard to write a useful specification.

I'd say you have conducted the perfect experiment to evaluate the system.

Now hang your favorite shirt on that same wall and see if you can range on it.

It will tell you if the sensor will find you (or your shirt) in this lighting condition.