Audio to LED circuit..

[[email protected]]

I'm looking for a circuit that will do the following. It will plug
into a headphone jack and will light up an LED when any audio signal
is outputted. The brightness of the LED does not vary depending on the
strength of the audio output or the volume of the device, it will
always be on when there is any audio signal and off when there isn't.
I will be sending it short pulses of audio, basically to make it blink
at a certain intervals. The specs of the LED are: 1.2VDC 29mA. I'd
like to try and use the smallest size battery as possible.

I've done a lot of circuit building, but not much design, so I would
consider myself a bit of a newbie. Any help?

 

[neon]

the word ANY AUDIO will gets into trouble 10microvolts is still audio. Neverthe less try an optoisolator driving leds it is the cheapest and less troublesome. just in-out

 

[Phil Allison]

The specs of the LED are: 1.2VDC 29mA.

** Really ??

Even red LEDs take 1.5 volts to make any light at all.

Other colours take higher voltages.


...... Phil

 

[[email protected]]

<[email protected]>




 **  Really ??

Even red LEDs take 1.5 volts to make any light at all.

Other colours take higher voltages.

.....  Phil

Sorry, forgot to mention it's an IR. Any help on a design?

 

[Phil Allison]

** Really ??

Even red LEDs take 1.5 volts to make any light at all.

Other colours take higher voltages.

..... Phil

Sorry, forgot to mention it's an IR. Any help on a design?


** Any help on what you are trying to do ?




...... Phil

 

[K Ludger]

Most basic idea I can think of right now is to use a comparator to
drive an LED..
However this solution may not yield a bright LED.


D from BC
myrealaddress(at)comic(dot)com
British Columbia
Canada

What about slaving a 74123 off the back of the comparator to keep the LED on
for a fixed minimum period. I used this years ago for detecting PCM signals.

 

[Jasen Betts]

I'm looking for a circuit that will do the following. It will plug
into a headphone jack and will light up an LED when any audio signal
is outputted. The brightness of the LED does not vary depending on the
strength of the audio output or the volume of the device, it will
always be on when there is any audio signal and off when there isn't.
I will be sending it short pulses of audio, basically to make it blink
at a certain intervals. The specs of the LED are: 1.2VDC 29mA. I'd
like to try and use the smallest size battery as possible.

I've done a lot of circuit building, but not much design, so I would
consider myself a bit of a newbie. Any help?

.-------------------------------------------------------------.
| This is an ascii schematic, if the diagram appears garbled |
| try switching to a fixed-pitch font (courier works well) |
| pasting it into notepad works well on ms-windows. |
| or in google groups "show original" (in "more options") |
`-------------------------------------------------------------'

LED
+3v---+--[33R]----->|----------------+
| |
+--[1K]--+--[100]--+ +
| | | /
|| | | |/ BC547
in >-----||----|---------+-[100]--|
|| | |\
| | \|
100nF +-->|---+ ~\
1N914 | |
| |
0V >-----------------+--------------+--

If the LED doesn't light brightly enough try a 1uF capacitor across the
C-E of the transistor.

if the LED doesn't get dark enough during silence add a 1K resistor in parallel with
it.

brightness may vary depending on the signal, but this should be OK for
morse practice etc.

 

[Phil Allison]

"Jasen Betts" <[email protected]

If the LED doesn't light brightly enough try a 1uF capacitor across the
C-E of the transistor.

** It's a fucking IR LED - you sheep shagging cretin !!

if the LED doesn't get dark enough during silence add a 1K resistor in
parallel with
it.

** It's a fucking IR LED - you sheep shagging cretin !!

brightness may vary depending on the signal, but this should be OK for
morse practice etc.

** It's a fucking IR LED - you sheep shagging cretin !!



....... Phil

 

[[email protected]]

I'm looking for a circuit that will do the following. It will plug
into a headphone jack and will light up an LED when any audio signal
is outputted. The brightness of the LED does not vary depending on the
strength of the audio output or the volume of the device, it will
always be on when there is any audio signal and off when there isn't.
I will be sending it short pulses of audio, basically to make it blink
at a certain intervals. The specs of the LED are: 1.2VDC 29mA. I'd
like to try and use the smallest size battery as possible.

I've done a lot of circuit building, but not much design, so I would
consider myself a bit of a newbie. Any help?

I'd rectify the signal then low pass and amplfiy to make "minimum"
input signal send output to rail. Put output through resistor and
LED.
One dual op-amp should do it.

George Herold