Chapter 10. Experiment 10: From Sound to Light

You can now create a noise-activated LED. Figure 10-1 shows the same circuit as before, with just five components added. A photograph is included in Figure 10-2.

meme 1001
Figure 10-1. This op-amp test circuit will flash the LED whenever the electret microphone picks up sound of moderate intensity.
meme 1002
Figure 10-2. The circuit with a noise-activated LED, breadboarded (9V battery is not shown).

An LED-Transistor Combination

After the output from the LM741 passes through the coupling capacitor, it reaches the ...

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