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Light sensor and automatic streetlight

Adjust ambient illumination and reference resistance to set a streetlight that switches on in darkness.

    E22 · Light sensor and automatic streetlight0.00 s · Ready

    Electronics · Sensors and analog signals / Principles and inquiry

    Light sensor and automatic streetlight experiment guide

    Adjust ambient illumination and reference resistance to set a streetlight that switches on in darkness.

    How does it work?

    With CdS as the lower resistor, the divider output rises as it gets darker.

    Key relationship

    Rcds = 10 kΩ(lux/100)^−0.7 · Vs = V Rcds/(R+Rcds)

    Try this investigation

    1. Adjust ambient illumination and reference resistance to set a streetlight that switches on in darkness.
    2. Run and record each of the three baseline presets.
    3. Compare the changed variable and its result with the baseline records.

    Interpreting your results

    Is the streetlight on with sensor output 4.17 V and a 3.5 V reference?

    On

    Assumptions and limitations

    A single representative CdS curve is used. Delay, device variation and comparator hysteresis are omitted. Experiment on screen; do not reproduce this with real power supplies, outlets or high voltage.