10 years, 7 months ago.

Nikki,

A simple idea would be to put a CDS photocell on one of the Analog-In pins. The CDS cell connected to 3.3V and the Analog-In pin together with a 10k resistor connected to ground and the same Analog-In pin. You may have to play around with the 10k value, depending on the CDS part you use.

...kevin

10 years, 7 months ago.

That's a wide open question... Much depends on what kind of sensor you want to use and what you want to measure about the light.

Sensor options include: photo transistor or diode, CDS cell, PIN photo diode, any number of TAOS light-to-something sensors.

Do you need to differentiate bright from dark? Or do you need to measure a continuous range of light values? Do you only need relative but finely graded light values or do you need to know absolute values (like for exposing film/sensors for photography)?

10 years ago.

What connections with the ARM board do we use to differentiate between light and dark using a CdS photocell? We are looking for HIGH (when bright) and LOW (when dark) inputs only.