Anyway to put EASY a VuMeter with a LED

[richon]

i want to put a LED (single Led) like a very simple and easy Vu-Meter somewhere in a stompbox i'm building.

any ideas?

[darron]

the signal from your instrument is an AC voltage. the louder you play the stronger the voltage becomes. similarly you want the LED to become brighter with higher voltage. so the problem you'd face is that the LED needs DC, and a much higher voltage than what your instrument puts out.

the best thing to do would probably be to tap off your audio signal, send it to a simple opamp, then rectify it (simple way to convert AC to DC), then maybe put a small capacitor in there to smooth out the fading in/out, then use your standard 1Kohm or so limiting resistor. the gain on the opamp would be a sensitivity control for the brightnes. you could skip the rectifier and capacitor for simplicity, but i would guess it would look nicer with it. i'd probably want a buffered signal too.


you could also play with an lm 3915 IC which gives a 10 LED meter. I mucked around with one:
http://www.dazatronyx.com/forums_etc/lm3915.mp4

[Herec]

Any word on this?

I'm actually interested in putting a VU meter in a pedal myself. It reacts to DC current, I'm not sure what its range is though.

The meter is from an old car analyzer.