555 Circuit Help Needed

[Howard]

Hello to all and thanks for reading. I am attempting to build a 555
circuit that will "listen" to audio output from a computer speaker
(hard wired to the speaker) and fire a relay and hold it for 5 seconds
after the music stops.

I put a Bowden 555 circuit together that fires the relay when a push
button is pressed and holds it for a 5 second time period.

I am looking for suggestions on a circuit that will replace the manual
push button, thus allowing the relay to remain energized while music
is playing.

Any help appreciated.

 

[JeffM]

I am attempting to build a 555 circuit
that will "listen" to audio output from a computer speaker[...]
and fire a relay and hold it for 5 seconds after the music stops.

It is good netiquette, before posting,
to READ some of the previous threads.

Bob Monsen laid out almost this identical project
barely 2 weeks ago in the BEGINNERS' group:
http://groups.google.com/group/sci....=*-*-bird-is-*-noisy+The.sound.detector&fwc=1

 

[Jim Gregory]

Hello to all and thanks for reading. I am attempting to build a 555
circuit that will "listen" to audio output from a computer speaker
(hard wired to the speaker) and fire a relay and hold it for 5 seconds
after the music stops.

I put a Bowden 555 circuit together that fires the relay when a push
button is pressed and holds it for a 5 second time period.

I am looking for suggestions on a circuit that will replace the manual
push button, thus allowing the relay to remain energized while music
is playing.

Any help appreciated.

You will need to modify /lengthen the 'audio' presence after amplifying it
to 'crushing' and rectifying its envelope to a DC level. Then, by a RC time
constant with electrolytics, make sure it ramps up fast and discharges
(decays) slower. This 'stretched' DC level will have to be amplified enough
to hold a relay on for about 5 secs. That's the gist. The 555 timing
function might be superfluous when audio is punchy and continuous.
Jim

 

[LVMarc]

Hello to all and thanks for reading. I am attempting to build a 555
circuit that will "listen" to audio output from a computer speaker
(hard wired to the speaker) and fire a relay and hold it for 5 seconds
after the music stops.

I put a Bowden 555 circuit together that fires the relay when a push
button is pressed and holds it for a 5 second time period.

I am looking for suggestions on a circuit that will replace the manual
push button, thus allowing the relay to remain energized while music
is playing.

Any help appreciated.

5 seconds is pushing the slow side and the R values to thelimimts. You
may want to add counter or use a time delay chip more suited to
##seconds, LSI logic makes a fine series of these delay timers...

Marc