How to Turn On LED with Audio ? - simple circuit

[Whoops]

Hi friends,

I need to build a simple circuit where Audio tuns on a LED,
I could do it with Arduino, but probably it's possible to do this with a much simple analog circuit than to use Arduino.

The goal would be, when there's audio in (Line Level) at the circuit input, the LED turns on, stays On for a 10 seconds, or Blinks (On and Off) for 10 seconds.

Is there anyone that could help me on this?

Thank you so much

 

[elskardio]

SparkFun make a simple sound detector that uses an electret microphone. The circuit could be easily modified to suit your needs... and there's already an LED indicator in the design.

https://www.sparkfun.com/products/12642?_ga=2.100548574.1336886560.1710119846-1860487470.1710119846

The schematic is available here:
https://cdn.sparkfun.com/assets/8/a/1/2/5/sound-detector-v11.pdf

 

[Whoops]

SparkFun make a simple sound detector that uses an electret microphone. The circuit could be easily modified to suit your needs... and there's already an LED indicator in the design.

That circuit goal is to connect it to a Text display to show a variable text number that reads the audio amplitube. It also has an Electret built-in Microphone and a simple mic preamp that I don't need, I will use it with Line Level.

I'm looking to build or buy something that it's much more simple, Live Level In, when Audio is present the LED lights up and stays on for a little bit.
It's just this

Thanks mate

 

[JohnRoberts]

Back in the late 80s a friend of mine didn't have a drummer for his band. He wrote (good) original music using a drum machine. When performing live in bars with his live bass player, he had a 6' tall cardboard cutout of a robot that would stand on stage with them. The name of his band was "robodrum".

I whipped up a simple one transistor circuit with a cheap microphone for input. The cardboard robot had red LED eyes that blinked along with the music.

Sorry no schematic, but not rocket science.

JR

 

[Whoops]

The cardboard robot had red LED eyes that blinked along with the music.

Yes, something as simple as that would work, I think.

I'm a Professional Mixing/Mastering Engineer,
I can do DIY projects without problems, but I have no formal Electronics education, so I'm not able to design circuits, even simple ones

So I gladly accept you help,
thanks

 

[JohnRoberts]

Think about what you want... are you thinking of a peak indicator? A signal present? A meter...?

There are simple circuits to do these.

JR

 

[kags]

Lots of info here:
Just modify threshold

https://www.sound-au.com/project146.htm

 

[Whoops]

Think about what you want... are you thinking of a peak indicator? A signal present? A meter...?

Don't know how to call it John,
but the goal is: when there's audio at the input the LED will turn on and stay On for 10 seconds,
After 10 seconds if there's no audio signal present at the input it will turn of.

What would you call this in terms of circuitry?

 

[Whoops]

Lots of info here:
Just modify threshold

https://www.sound-au.com/project146.htm

Nice One, thank you so much my friend,
that would work well for most of the duty, I would just need that the LED would stay On for litle longer after the signal is detected, instead of turning off right away when the signal is not present.

Maybe this circuit can be modified for that,
do I need a sort of timer circuit for that?

Thanks

 

[kags]

A 555 timer circuit or possibly a supercap could both work- others prob know better the cost vs benefits of each.

 

[JohnRoberts]

Don't know how to call it John,
but the goal is: when there's audio at the input the LED will turn on and stay On for 10 seconds,
After 10 seconds if there's no audio signal present at the input it will turn of.

What would you call this in terms of circuitry?

To light the LED for 10 seconds is called a one-shot or a monostable multivibrator. The ne555 is/was one. Then you need to boost/condition the audio adequately to trigger the one shot.

Maybe search for typical 555 circuits.

JR

 

[SoundBlaster]

Look at NJM2072. Or roll your own based the schematic. This IC is used in a lot of products for automatic input sensing. The capacitor at pin 5 determines how long the output stays latched after a signal is removed.

 

[Whoops]

A 555 timer circuit or possibly a supercap could both work- others prob know better the cost vs benefits of each.

Thank you

To light the LED for 10 seconds is called a one-shot or a monostable multivibrator. The ne555 is/was one. Then you need to boost/condition the audio adequately to trigger the one shot.

Maybe search for typical 555 circuits.

JR

Thank you

Look at NJM2072. Or roll your own based the schematic. This IC is used in a lot of products for automatic input sensing. The capacitor at pin 5 determines how long the output stays latched after a signal is removed.

Thank you

 

[JohnRoberts]

Interesting... I did not see a typical application circuit, but data sheet reveals 7V PS max, and roughly 2 second hold time after signal is removed.

JR

 

[Hubbub]

The NJM2072 block diagram is the application circuit, although I'd add a power supply bypass cap of 0.1uF. The input coupling cap is chosen as you need to ignore lower frequencies. Here 0.1uF puts the low corner at 80Hz. The input is rather sensitive, for line level add an attenuator (20-30dB?) before the input cap. For your indicator add a 1K resistor from V+ pin to an LED to ground, connect pin 6 to the node between resistor and LED. Since the 10uF cap gives 2 seconds use a 47uF cap at pin 5 for a 10 second delay. Got no +5V but have +15V power? use a 9V zener from +15V to the V+ pin.

 

[Voyager10]

Here's a sketch of how you might do it with a 555:



For a 10s time you'll need a CMOS one, TLC555 or TS555 (https://www.st.com/resource/en/datasheet/ts555.pdf).

This is basically just the standard 555 'one-shot' circuit. The output pin 3 will drive a small LED directly (the 470R resistor gives about 6mA through the LED).

The circuit is triggered whenever pin 2 goes below 1/3 of the supply voltage. The 47K resistors and the trimmer put a DC level adjustable between 1/3 and 2/3 the supply voltage on pin 2, and any (negative) peaks in the input signal will then take it below the threshold. The trimmer therefore sets the input sensitivity.

The TS555 will operate from 2V to 16V, although the LED won't work much below 3V, and you'll need to increase the 470R resistor for higher voltages.

 

[Hubbub]

The 555 will not give a 10 second delay from the last audio, it will give you 10 seconds from the start of the audio. What is needed is a re-triggerable monostable, which the 555 is not. The NJM2072 looks like the best and simplest approach so far, it is re-triggerable.

https://www.mouser.com/datasheet/2/294/NJM2072_E-1375739.pdf

 

[Whoops]

The 555 will not give a 10 second delay from the last audio, it will give you 10 seconds from the start of the audio.

That's totally fine, the LED just needs to stay on for a little bit after the audio starts, it doesn't matter if its 10 seconds after the audio ends or 10 seconds when the audio starts.
Both work well, actually I was thinking about 10 seconds after the start of the audio (or at the start)

 

[JohnRoberts]

Most typical circuits will start hold time from when the signal stops, and keep resetting it as long as signal is playing.

JR

 

[Whoops]

Most typical circuits will start hold time from when the signal stops, and keep resetting it as long as signal is playing.

JR

That's good also, it would work well