Datasheet

Measuring Light

As we've said, a photocell's resistance changes as the face is exposed to more light. When its dark, the sensor looks

like an large resistor up to 10MΩ, as the light level increases, the resistance goes down. This graph indicates

approximately the resistance of the sensor at different light levels. Remember each photocell will be a little different so

use this as a guide only!

Note that the graph is not linear, its a log-log graph!

Photocells, particularly the common CdS cells that you're likely to find, are not sensitive to all light. In particular they

tend to be sensitive to light between 700nm (red) and 500nm (green) light.

Basically, blue light wont be nearly as effective at triggering the sensor as green/yellow light!

What the Heck is Lux?