Best way to make LEDs flash in time with a music source


Could someone suggest the best circuit to make LEDs flash in time with a music source directly connected to the circuit? BTW the circuit needs to run off batteries, I've seen circuits using TIP31 transistors, but are they any good?

Best Answer

There's a website for analog audio circuitry that I really like:

In keeping with the author's request, I've only provided a link to the home page, but if you add these to the end of the URL, you'll get:

  • /project60.htm
    • LED volume meter
  • /project136.htm
    • Real-Time Analyser (RTA), basically a full spectrum of what's happening at the moment
  • /project62.htm
    • Complete lighting system, including a "Sound to Light" (S2L) module at the bottom of /project62a.htm

Perhaps you could adapt one of those?

Or if all you want is to flash a single LED in sync with, say, the kick drum, then you could use a dual opamp to:

  1. Lowpass the signal so you're more likely to trigger on the kick rather than the hihat
  2. Compare the result to some reference level

The result of that can either drive the LED directly if the opamp is strong enough, or feed a transistor.