Resistive Light Sensor

Overview

In this lesson you will be measuring the light level in the room using a photocell. A photocell is a resistor that varies the value of its resistance based on the level of light that strikes its surface.

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Exercise:

  1. Construct the circuit shown below.

    _images/image43.png

  2. Measure the voltage at the output using a multimeter.

  3. Copy the following table into your note book and record voltages when the photocell is covered with the following materials.

    Light Sensor

    Sensor Block

    Voltage

    Uncovered

    Paper

    Tape

    Pinky

    Thumb

    Wood

    What would account for the different voltages and light levels? Can light pass through these objects?

    TEACHER CHECK ____

  4. Connect the output of the light sensor circuit to one of the analog pins on your Metro Mini.

  5. Write a program to read the value of the output and print it in the Serial Monitor in a single column.

  6. Note the changes in values in different light levels.

    TEACHER CHECK ____