Vex Light Sensor

[swe9]

Originally Posted by Don Rotolo

Basically, it is a standard CdS sensor which has low resistance in bright light and high resistance in darkness. Since it carries the current from the +5 supply to ground, the analog sensor has a value of about 0 in bright light, and about 255 in darkness.

The Inventors Guide on the item is here.

If you mean the specific characteristics of the CdS device used in the Vex product, I don't have that info, but I am sure Vex Labs would answer that in their forum.

Don

I purchased a defective light sensor, so I have some graphs of the performance of both a good and a bad sensor. The good sensor returned values from 78 to 970 and had a sharply vertical responsde. The bad sensor was diagnosed as having a defective pull-up resistor and went vertical early but had a long exponential tail that kept it from settling on a value for a very long time. The low/high values could have been related to the amounts of light I had but seem representative of the range 0-1000 or 0-1024.