The Cyber-Spy.Com Usenet Archive Feeds Directly
From The Open And Publicly Available Newsgroup
This Group And Thousands Of Others Are Available
On Most IS NNTP News Servers On Port 119.
Cyber-Spy.Com Is NOT Responsible For Any Topic,
Opinions Or Content Posted To This Or Any Other
Newsgroup. This Web Archive Of The Newsgroup And
Posts Are For Informational Purposes Only.
From: firstname.lastname@example.org (N. Thornton)
Subject: Re: powering a bulb or led(s) with audio amplifier?
Date: 23 Oct 2002 08:17:32 -0700
NNTP-Posting-Date: 23 Oct 2002 15:17:32 GMT
> "Adam Bowen" schrieb im Newsbeitrag
> > I'm interested in hooking up light-emitting devices in parallel with a
> > home stereo speaker. I just want it to glow with the overall amplitude.
> > I've read most stereo amps push 4-30V; don't know if this is true. Seems
> > like basic DC lamps should work, but I"ve never tried it. LEDs would be
> > cool - ideally, those sequenced flashing RGB leds. If necessary, I could
> > run the light device on a separate channel and rig whatever circuitry's
> > necessary.
> > Any ideas about these, or zanier options? (this is for an art project)
> > Thanks,
> > Adam
> Now take a 10 ohms resistor and connect a bridge rectifier in series with
> it. Put an electrolytic capacitor 100uF/40V to the + and - output
> and you can drive a LED with a current limiting resistor.
> To calculate the resistor:
> Upeak - 1.4V - Uled(1.8V red, 2.2V gn, 3.5V blue) = Ures;
> Ures/0.03A = value of resistor in Ohms reduce it by the 10 ohms of the other
> resistor. With a higher valued capacitor you can make it less flickering.
> If the amplifier is small and the additional voltage drop through the bridge
> rectifier lights the led only at higher volume:
> put two leds antiparallel and connect through a common resistor:
> (Upeak-Uled)/0.03A= resistor
> Both devices shouldn't affect the sound, so you can connect them to the
> speaker terminals.
A bicolour LED, whcih contains 2 back to back LEDs within it, in
series with a resistor would be far simpler. The frequencies in use
are too high to cause eye problems.
To get it to follow the bass beat better, use as much inductance as
poss in series with the R. Reduce the resistnace value by the
To get more change in light level, use 2 back to back zeners in
series, and adjust your R value as the R will have lower V to deal
And dont be afraid to give the LED twice its rated current at peak: it
wont be running on d.c.
Go Back To The Cyber-Spy.Com
Usenet Web Archive Index Of
The sci.electronics.design Newsgroup