Re:Measuring keyboard-to-photon latency with a light sensor
by mncharity on Tuesday June 02, 2020 @04:40PM
(#23396043)
> You can see that some combination of the light sensor and the monitor take nearly 100ms to fully transition.
That's the sensor. It's not a wonderful match for this job.
The linked[1] light sensor module looks like a CdS photoresistor. In its Amazon Q&A, the seller claims "The response time: Rise 30ms Decline 30ms", under unspecified conditions.
Better to use a phototransistor like [2], with a rise time of microseconds. 4 orders of magnitude faster. It's easy - one resistor, and an analog input on the Teensy.
Deja vu. For 3D UI prototyping on my laptop, I diy'ed LCD shutter glasses driven by an arduino with a photosensor reading a white/black square rendered flashing in a screen corner. IIRC, I actually tried a photoresistor first, but the plotted screen response curve times weren't plausible. Only then did I look for a datasheet, and had an "okaaay, that's not the right thing" moment. :/
That's the sensor. It's not a wonderful match for this job.
The linked[1] light sensor module looks like a CdS photoresistor. In its Amazon Q&A, the seller claims "The response time: Rise 30ms Decline 30ms", under unspecified conditions.
Better to use a phototransistor like [2], with a rise time of microseconds. 4 orders of magnitude faster. It's easy - one resistor, and an analog input on the Teensy.
Deja vu. For 3D UI prototyping on my laptop, I diy'ed LCD shutter glasses driven by an arduino with a photosensor reading a white/black square rendered flashing in a screen corner. IIRC, I actually tried a photoresistor first, but the plotted screen response curve times weren't plausible. Only then did I look for a datasheet, and had an "okaaay, that's not the right thing" moment. :/
[1] https://www.amazon.com/gp/product/B01N1FKS4L/ [2] https://www.adafruit.com/product/2831