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Photo cell (CdS photoresistor)


  • Model: 161
  • Shipping Weight: 0.015Kg
  • 50 Units in Stock
  • Manufactured by: Adafruit

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Description: CdS cells are little light sensors. As the squiggly face is exposed to more light, the resistance goes down. When it's light, the resistance is about ~1K?, when dark it goes up to ~10K?.

To use, connect one side of the photocell (either one, it's symmetric) to power (for example 5V) and the other side to your microcontroller's analog input pin. Then connect a 10K pull-down resistor from that analog pin to ground. The voltage on the pin will be 2.5V or higher when it's light out and near ground when it's dark.

For a full tutorial with wiring diagrams, code examples, and project ideas, please read Adafruit's photocell tutorial page!

Technical Details:

  • Length: 4.46mm/0.18in
  • Width: 5mm/0.20in
  • Height: 2.09mm/0.08in
  • Weight: 0.25g/0.01oz
  • CdS photocells are not RoHS compliant


  • As of Dec 15, 2019 the resistance range has changed to 1K-10K: Datasheet

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