A digital multimeter is preferred for precision work, ... Digital multimeters have numerical displays, like digital clocks, for indicating ... readout
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5.10. PULSED-LIGHT SENSOR
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voltage when exposed to light, in a manner not unlike a semiconductor solar cell. By itself, the LED
does not produce enough electrical power to drive the audio detector circuit, so a transistor is used
to amplify the LED's signals. If the LED is exposed to a pulsing source of light, a tone will be heard
in the headphones.
Sources of light suitable for this experiment include fluorescent and neon lamps, which blink
rapidly with the 60 Hz AC power energizing them. You may also try using bright sunlight for a
steady light source, then waving your fingers in front of the LED. The rapidly passing shadows will
cause the LED to generate pulses of voltage, creating a brief "buzzing" sound in the headphones.
With a little imagination, it is not difficult to grasp the concept of transmitting audio information
such as music or speech over a beam of pulsing light. Given a suitable "transmitter" circuit
to pulse an LED on and off with the positive and negative crests of an audio waveform from a
microphone, the "receiver" circuit shown here would convert those light pulses back into audio
signals.
Summary :
Given a suitable "transmitter" circuit to pulse an LED on and off with the positive and negative crests of an audio waveform from a microphone, the "receiver" circuit shown here would convert those light pulses back into audio signals.
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light,led,audio,circuit,signals,oltage,pulsing,power,pulses,exposed,source,headphones,rapidly