Ambient light sensor response time

[espena]

I am thinking of adding a VEML7700 ambient light sensor to a NTP/GPS timed LED clock that I'm working on in order to auto-adjust the display brightness.

By placing the light sensor beneath the front glass among the LEDs (which is pretty much my only option), it will be disturbed the brightness of the display. So I will have to turn the display off to do a proper ambient light readout (or simply sync the VEML readouts with the PWM drivers).

I was thinking of blanking the display for a very few milliseconds, reading the ambient light and then turn the display back on. Since I want the adjustment sequence to be unnoticeable for the human eye, I'm granted only a few milliseconds. Probably at or below 10 ms.

Is VEML7700 sufficiently responsive for this to work? How much time will the sensor need to settle? Normally, I would say that 10 ms is an ocean of time -- perhaps not quite so in this case...

I tried to find some clues on whether my approach will work from the datasheet https://www.vishay.com/doc?84286, but to no avail. It might be possible to deduce something from the i2c timing characteristics.

Is there anyone here having experience with ambient light sensors and response time? Either for the VEML7700 specifically or in general?

[PlainName]

The datasheet gives a refresh time, based on the integration time and power saving mode. It lists 600ms as not quite best value (doesn't give data for 50ms integration time). Bottom of page 9.

[Algoma]

The display brightness is a known value, it can be calibrated out. Perhaps take frequent readings with the display on, adjusting for the known brightness. Then Blank it to take cailibration readings every minute when the time changes. A display flicker with a digit change will be less noticable. Or only blank the (minute) digit nearest the sensor, the one that is changing the most often.

[eutectique]

VEML7700 has programmable integration time from 25ms to 800ms (register 0, bits ALS_IT). Nowhere near 1ms. Here is the application note.

[espena]

Oh, it was there all the time, in my face (I swear, I did read the doc, but not thoroughly enough, obviously). Thanks! Far too long integration time. I guess I will have to try calibrate out the display's illumination instead, as  suggested by Algoma.