Audio Jack Short

Other Hardware Audio
1

Hey guys I just recently made a project for my band.
The scope of the project is to receive audio from my guitar/pedal-chain and "translate" that audio to light on an addressable ledstrip.
Tried the circuit by powering my Arduino through the usb. And that worked fine. Actually much better than expected.

Then I tried powering the Arduino through a power supply and suddenly my guitar pedals switched off. So I guessed that the audio jack should be carrying voltage already. I disconnected the jack from the pedal chain and measured the voltage on the tip/sleeve of the jack. And as expected the jack carried around 5v.

Can anyone point what I am doing wrong here? Bellow you will find a poorly drawn schematic of my connections.

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2

Your linking to google did not work too well :wink: Below you attached image.

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PS
This is the errro that I get when I try to access https://lh6.googleusercontent.com/PrU9SbgeULxpNbQZtkU-PTgemfxhc6rWfu2yKlEX48a1R4OVGr72nvtwzYcLXxw-fCTFfJGm4670d8oQkxIy=w1920-h920-rw

  1. That’s an error.

Your client does not have permission to get URL /PrU9SbgeULxpNbQZtkU-PTgemfxhc6rWfu2yKlEX48a1R4OVGr72nvtwzYcLXxw-fCTFfJGm4670d8oQkxIy=w1920-h920-rw from this server. (Client IP address: aa.bb.cc.dd)

Forbidden That’s all we know.

3

You may want to consider an OPTO ISOLATOR between your main rig and the Arduino.
An some stage equipment the signal may be too much also and you might have to buffer it in some form.

Easy way to test those aspects is to feed a known signal to the Arduino.
Or as a very simple test hook up a phone or mp3 player to the Arduino to make sure it works as expected.

You have the common ground which is a wise thing to do between the leds and the power supply and arduino.

4

Tried the circuit by powering my Arduino through the usb. And that worked fine. Actually much better than expected.

Then I tried powering the Arduino through a power supply and suddenly my guitar pedals switched off.

That shouldn't have happened.

So I guessed that the audio jack should be carrying voltage already. I disconnected the jack from the pedal chain and measured the voltage on the tip/sleeve of the jack. And as expected the jack carried around 5v.

The voltage on an unconnected pin is floating and "undefined" and it's possible for it to float-up to 5V. But the meter should pull it down to zero (or near zero) so I'm betting the Arduino is fried. Hopefully your pedal isn't also fried!

Do you have any resistors? A resistor between A0 and ground will pull the voltage down to ground (about zero volts). A 1M resistor would be great because that's in the ballpark for a guitar pickup, but a 10K resistor would also be a valid experiment. If you're still getting 5V, the Arduino is bad or A0 might be programmed as an output (software error).

Or as a more complete test try [u]Analog Read Serial[/u] with a potentiometer.

The Arduino can be damaged by negative voltages, including the negative half of an AC audio signal. That shouldn't happen with a direct guitar connection but it could happen with a pedal (lower impedance and more current capability).

It's also possible you "zapped" the Arduino with a [u]static discharge[/u] when you touched the circuitry.

The normal solution for handling the positive & negative halves of an audio signal is to bias the input at 2.5V. The schematic for the standard bias circuit is attached to [u]this post[/u]. But for a guitar, increase the resistors to 1M or more. (The capacitor in the bias circuit will also isolate/protect your guitar & pedals from any DC voltage.)

With the bias, silence will read about 512 on the ADC and your audio readings will be centered around 512. Depending on what your software is doing you may want to subtract-out the bias.

You may want to consider an OPTO ISOLATOR between your main rig and the Arduino

No... Opto-isolators are digital (non-linear) and a guitar pick-up can't drive the internal LED.

5

I once built an effects peddle rack for my son. I found I could not power all of them off the same supply because it was impossible for them to share a ground due to the ground lift resistor in some of the peddles. The attempt to do so burned out the resistors.

I assume the same sort of thing is happening here.

If you have 5V on the audio jack you can remove it by placing a series capacitor, about 16uF, before feeding it into the audio input of the Arduino. Make the positive end of the capacitor go to the jack.

6

DVDdoug:
That shouldn't have happened.
The voltage on an unconnected pin is floating and "undefined" and it's possible for it to float-up to 5V. But the meter should pull it down to zero (or near zero) so I'm betting the Arduino is fried. Hopefully your pedal isn't also fried!

Do you have any resistors? A resistor between A0 and ground will pull the voltage down to ground (about zero volts). A 1M resistor would be great because that's in the ballpark for a guitar pickup, but a 10K resistor would also be a valid experiment. If you're still getting 5V, the Arduino is bad or A0 might be programmed as an output (software error).

Or as a more complete test try [u]Analog Read Serial[/u] with a potentiometer.

The Arduino can be damaged by negative voltages, including the negative half of an AC audio signal. That shouldn't happen with a direct guitar connection but it could happen with a pedal (lower impedance and more current capability).

It's also possible you "zapped" the Arduino with a [u]static discharge[/u] when you touched the circuitry.

The normal solution for handling the positive & negative halves of an audio signal is to bias the input at 2.5V. The schematic for the standard bias circuit is attached to [u]this post[/u]. But for a guitar, increase the resistors to 1M or more. (The capacitor in the bias circuit will also isolate/protect your guitar & pedals from any DC voltage.)

With the bias, silence will read about 512 on the ADC and your audio readings will be centered around 512. Depending on what your software is doing you may want to subtract-out the bias.
No... Opto-isolators are digital (non-linear) and a guitar pick-up can't drive the internal LED.

Sorry guys for my absence, but many things happened in the meanwhile...
So, i tried the 1M resistor between A0 and the gnd, the voltage seems to be around 1,20... So i guess i "fried-up" my uno?

7

So, i tried the 1M resistor between A0 and the gnd, the voltage seems to be around 1,20... So i guess i "fried-up" my uno?

Maybe, but I wouldn't pronounce it dead just-yet.

Is that with nothing else connected? Is that voltage measured with a multimeter or with the Arduino itself?

…With 1M you could be picking-up noise.

If you have a 1K or 10K pot, try the [u]Analog Read Serial Example[/u].

If you don't have a pot run the Analog Read Serial and ground the input and you should read zero. Then connect the input to 5V and you should read about 1023.

If either of those fail you can assume the Arduino is bad.