Audio noise..

Hey all,
First off, I’m a newbie…

I’m using an Arduino to control a relay, which would then control the on/off state of another circuit, powered by AA batteries. To cut things short, the controlled circuit is then connected to a speaker.

The problem :
I’m hearing a buzz through the speaker. I tried troubleshooting it, and i found out the buzz can only be heard when the Arduino is powered (with USB, wall adapter or battery).
Since the Audio circuit is only connected to the Arduino through the relay, is it possible that it is causing the buzz?
Would a solid state relay solve this problem?

Any inputs are greatly appreciated.

Thanks!
Anis :-?

To cut things short

Please dont :). What exactly is the other circuit doing? And what are its components?

LOL… ::slight_smile:

The other circuit is from a Sony walkman…
A speaker is connected to the walkman circuit audio output, then the relay, controlled with an Arduino, is switching the circuit on and off.

:-/
Best,
Anis

then the relay, controlled with an Arduino, is switching the circuit on and off

So there is no connection electrically between the walkman and the arduino? relay contacts don’t count as they are not connected to the arduino.

Yea… No electrical connection between the arduino and the walkman circuit. But,yea… the relay is connected to the arduino…

Still puzzled,
Anis
:-?

Reed relay with a coil around the switch contacts?
Induced noise?
Just guessing here. (in the absence of a circuit)

What is happening is that your walkman is picking up electrical noise from the arduino. I suspect that it will do this without the relay connection.

It might be it is picking it up on the long power wires going out to the relay. You can improve this by putting extra decoupling capacitors across the supply feeding into the walkman, as close to the walkman as you can.

De-coupling

Thanks! I will try it out…

Btw, I changed the relays to TIP120 transistors… Still buzzing…

Another question…
Eventually, i would want my project to not run on batteries. I tried getting the different voltages i need from a 12vdc wall adapter using LM317s… but, it causes even more audio noise/buzz/hum from the speakers… Tried using a Behringer hum destroyer, supposed to kill ac hums, but it didn’t work…

Any suggestions? I’m thinking of trying out a computer power supply, but i don’t know if it would make any difference…

Thanks again!!
Anis
:slight_smile:

I changed the relays to TIP120 transistors… Still buzzing…

That is not a surprise, why would the transistor type make any difference?

The problem with a mains supply is that you need it to have a low ripple voltage.

I’m thinking of trying out a computer power supply,

Probably not a good idea as those are designed for digital circuits and so can have more ripple generating even more noise.

What frequency is this hum? Is it 50/60 or 100/120Hz? If so it is from the mains. If it is a higher frequency it is from a switching power supply and you might be better going for a liner regulator and supply.