I ripped 2 analog VU meters from some old stereo I found in the trash, and I'm not exactly sure how I should go about using them. They rarely respond to the output of my stereo but that is expected.. how do I beef up the signal to get them to respond the right way? I also assume I need to tune them to properly show the real signal strength, how would I go about accomplishing that?
You'll need 2 things, an op-amplifier stage to adjust the signal to the standard level, and a "perfect rectifier" (typically an opamp with a rectifier diode in the feedback loop so there's no voltage loss) to convert the AC music signal to varying DC. Can be done with cheap dual or quad opamps, sound quality won't be affected. Calibrating to the standard dB levels could be done with a signal generator and multimeter (plus a read at the spec) or maybe a Test CD. I think circuits have been covered here before, or there's a slightly different approach here.
<3 ESP's site, learned a lot from him, also bought two of his projects. anyway, i'll look into what you said, thanks looks like ive got a bit of expirimenting to do with no info on these meters. glad my school has all the necessary equipment
Also check the LM3915/6 datasheets, I thing they give an example circuit for the preamp/rectifier stage.
