Protect analog pin from negative voltage

can someone tell me what i need to protect my analog pins from negative voltage? I am trying to input audio from PC headphone jack I need to test volume, or pitch, Like is it loud or soft, or is it high pitched or is it low pitched. 2 possible conditions. thanks

Use a Schottky diode from ground ( anode ) to input (cathode).
Having said that you should be biasing that input correctly so that you don’t have a negative input in the first place. In effect you will get a half wave rectified signal.

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Thank you for your response:
I know I look smarter than I am but, Technical terns are not my strong suit. what is biasing and how do I do it. Please remember I’m old and don’t have a lot of time like I used to.

A DC offset or shift on a signal.

for an AC signal like this:-
Audio Bias

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Ok here comes what I don’t understand most. do I need the Schottky diode and what looks like a voltage divider. or is the divider enough by itself, And I really appreciate your help.

No there is no diode in that diagram.

No you also need that capacitor. The capacitor removed any direct coupling between your input and the Arduino input and the potential divider produces the DC shift or biasing. This is good for AC signals up to 2.5V peak to peak.

ok thank you. I’ll get right on it. Lets see what i can screw up.

or 5 ?

5 V peak to peak means 2.5 V peak in either direction.

From a lazy old timer: A simple series resistor will provide the best protection you could need. Each input of the processor has internal diodes connected to Vcc and other to GND. If the voltage on any pin exceeds Vcc by ~ 0.7 volts these diode start to conduct. I do it all the time, I size it to keep below a few mills and under 10K.

Thanks Mike and all the rest of you , I made my little project work because of you. who says you can’t teach an old dog new tricks. you just need a 2x4 Thanks all I don’t know where else to put this.

In this context what is “this” ?

this is (was) the thank You. Boy you are Grumpy. lol

It’s my job :wink:

good enough.

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