Audio input to microcontroller

[pavans2510]

I want to input the analog signal to analog port of arduino. Since the audio input signal is ac and arduino's ADC range is 0 to 5v. I increased the dc offset level of the ac signal to 2.5v as shown in picture below. But the problem is that there is some amount of noise induced, I don't know from where. Even if the input audio is muted I get some variations around 2.5 volts to the arduino. Should i insert any circuitry into this or is there any other solution to this?

 

[FoxyRick]

Your resistors are quite high - high impedance is more prone to noise. Try 10K.

The other thing is your power supply - how 'clean' is it? I'm not familiar with the Arduino, but when I do ADC on PIC's the power supply, and especially the separate analogue supply input when available needs to be very clean. With just a cheap, switch-mode PSU as the main power source the ADC twitches all over the place!

 

[pavans2510]

FoxyRick thanks for the reply,
I'm using on board 5 v power supply and that is causing the problem.
I tried to change resistor values from 100k to as low 180 ohms in steps with wiring as shown in the picture below. But in every range there was noise present. As the resistor values reached around 1k the noise level was reduced to some extent but not fully. Is there any method to filter out the power supply noise?

 

[godfreyl]

Can't you just use a capacitor to filter the bias voltage?

 

[pavans2510]

Thanks for the circuit godfreyl.
Tried with that circuit but with no change. There are still minor noise present at the audio input. Are there any other ways to filter out the power supply noise?

 

[D.A.(Tony)Stewart]

Use low ESR caps close to V+ in and use ferrite choke or beads before Vin. If you short audio input with a large cap to ground and still get noise, then your V+ and V ref are too noisy.

 

[jignesh.patel47]

hi,
I want to take a only audio output from set-top box or any other receiver of TV through RCA cable or RF output on microtroller.I want to know how can i take it on my controller ADC and also which extra circuit require between microcontroller and out put of set-box.

Thanks in advance

 

[crutschow]

What is the value and frequency of the noise?

- - - Updated - - -

hi,
I want to take a only audio output from set-top box or any other receiver of TV through RCA cable or RF output on microtroller.I want to know how can i take it on my controller ADC and also which extra circuit require between microcontroller and out put of set-box.

Please don't hijack a thread with your questions. Start a new one of your own.