Analog Pins printing Wrong values

system · November 8, 2011, 5:51am

Hi i m new to Arduino. Now i m at interfacing basic sensors with arduino. and my issue is while getting data from the simple IR Sensors and printing in the serial port, i m getting some others values which is not corresponds to the sensor's output. Even when i unplug the sensors from the input port i m getting values(Without any input i m getting some values in serial)!!!. whats the problem? Why it is giving me some floating Values?

retrolefty · November 8, 2011, 8:08am

Why it is giving me some floating Values?

Because when you read a analog input pin that has nothing wired to it, you have a "floating" input pin condition and the value your read will just be noise and capacitive coupling to other input pins, etc, that is normal. Wire the pin to ground and see if you have a steady zero value, then wire the pin to +5vdc and you should see a steady 1023 count value. The analog input pins like to 'see' a signal source impedance of 5k ohms or less for most stable readings. What is the sensor type and do you know it's output impedance value? Perhaps a link to the sensor would help us.

Lefty

Grumpy_Mike · November 8, 2011, 9:02am

See:-
http://www.thebox.myzen.co.uk/Tutorial/Inputs.html

By the way the description of this section says:-

For problems with Arduino itself, NOT your project

In what way does your problem conform to this description?

Pleas post in the correct section!

system · November 9, 2011, 5:33am

Hey Retrolefty Really Thanks For your Quick Reply .As u said i did the Analog pin reading with the Ground and Vcc(+5V) of the arduino it was not exactly o and 1023 but it was (+ or -)10 to that and I'm Using Arduino Diecimila its Fine i think the Board is good and i'm able to read Analog Values But When i connect this Analog Sensor(http://bit.ly/uME9Mb ) When I connect Vcc and Ground to the Board and Signal to the 0th pin of Analog Port to output signal of the Sensor,And when Sensor is Placed without Any movement, I'm getting these values

And i'm using Standard Arduino Analog Serial Read Sketch Which is given Below:

void setup() {
Serial.begin(9600);
}

void loop() {
int sensorValue = analogRead(A0);
Serial.println(sensorValue, DEC);
}

Thanks in Advance

Moderator edit: Whitespace trimmed. Obnoxiously long list put inside [code] [/code] tags.

system · November 9, 2011, 5:37am

Sorry As Grumpy_Mike quoted my post shouldn't to be here so i'm posted my Post on This link (http://arduino.cc/forum/index.php/topic,78393.0.html) And Thanks to Retrolefty For Your Quick Reply

retrolefty · November 9, 2011, 5:43am

I've used a similar (but a shorter range model) module. The device doesn't have a accuracy or variation spec but there are two things I can think of that you can try and do to help stabilize the readings.

Mount a filter capacitor, say 10 ufd right at the + and - terminals on the sensor.
Learn to use averaging methods in your coding, say take 8 readings in a row, sum them and then divide by 8 and then send that value out the serial port. See if that doesn't give you smoother values.

Lefty

system · November 10, 2011, 10:03am

Yaahhhh.... It's working good(But the Values are Little Bit Not Accurate :)). I'm Happy and Thanks

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Analog Pins printing Wrong values

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