analogRead

Forum 2005-2010 (read only) Hardware Troubleshooting
1

Hello,

In an arduino mega analog pins are consistently displaying value with no hardware connected.

Test code is below, with serial monitor results.
All pins have this behavior of reading values ~300 without input.

I am expecting zero, any hints?
Is something broken?

Thanks, cnash.

/TESTCODE/
const int Pin1 = 3;
int ANALOG_PRESS_LEVEL = 0;

void setup() {
Serial.begin(2400);
Serial.print("ALIVE_#");
}

void loop(){
ANALOG_PRESS_LEVEL = analogRead(Pin1);
Serial.print(ANALOG_PRESS_LEVEL,DEC);
Serial.print(", ");
delay(1000);
}

/OUTPUT/
ALIVE_#390, 335, 329, 327, 325, 324, 324, 324, 323, 323, 323, 324,

2

As the pins are not connected to 0V or 5V the are floating just in between. Connecting a resistor between pin and GND helps.

Please read this tutorial that explains all http://arduino.cc/en/Tutorial/DigitalPins

3

Thank you. My mistake. Corrected many months ago with the information referenced. Porting proof of concept to prototype introduced pull-down-resistor wiring error(trying to combine them). This indeed was the solution.

Best Regards,
Nash