CdS cells are made of Cadmium Sulfide which has the interesting property of changing resistance when exposed to light. Typically, the more light its exposed to, the lower the resistance. It's also one of the easiest sensors to use. This particular CdS cell has an approximate head diameter of 5mm.
A typical application circuit consists of a simple voltage divider where the CdS cell sits on the bottom resistor. The output of the voltage divider just gets fed into an ADC. As the resistance changes, the voltage can be directly measured in the ADC and translated into a light reading.
These CdS cells have the following specs (min, typ, max):
- Resistance: (25, 42.5, 60) kohm @ 10 Lux
- Min dark resistance: 1 MOhm
- Max voltage rating: 100V
- Peak spectral response: 550 nm
- Manufacturer: Macron
- Model: MI5527