how to detect that the VL6180 sensor beam is totally blocked (the sensor directly touches an object)?

[JBM]

Greetings.

how to detect that the VL6180 sensor beam is totally blocked (the sensor directly touches an object)?

When an object touches and blocks the VL6180 sensor, the sensor returns distances of 255 mm and typically the error message: ECE (Early convergence estimate) failure / Signal/Noise error / No convergence.

The sensor returns exactly the same status when objects are too far away.

 

How can I detect that an object is mistakenly lying and blocking the sensor so that it does not work as it should?

 

Kind regards

Joergen

[John E KVAM]

I don't have an answer, so these are some ideas in a random order. 

One difference I can see between a completely blocked sensor and one with no target would be the amount of ambient light. It's possible, I suppose, that in a room with no windows and only LED lighting, you would have a 'no ambient' situation, but generally you could use that. Might not work at night though. 

Another thing would be to provide your own tiny target. Something just out of the FoV that would return a very faint signal. Something dull enough so it doesn't throw off your main target distance, but gets a few photons. 

Perhaps you could turn off ECE every now and again. Just to check for the 'blocked' case?

Another thought... With a coverglass, a number of photons are reflected through the glass. If the glass were blocked, I'd expect a larger number of photons to be reflected. Could you -every now and again- turn off the ECE and get a measure of the crosstalk? I think that might do it. But it would take some testing. 

Great question though. 

[JBM]

Thank you John.

I will try the solution with protective glass and experiment with ECE. In all circumstances, it is necessary to protect the sensor from dust and dirt in order to ensure stable operation in the environment in which the sensor is to be used.

 

Kind Regards

Joergen.