Arduino Nano incorrect analogReading values

Question

I'm new in using Arduino, just recieved board from china today. Arduino Nano 3.0 clone (CH340). I installed drivers, everything worked at the first try. Tried to blink diode on it without problem.

Then I connected LM35Z (temperature chip) using built in voltage source. But I keep getting really weird values. They goes from 0 to 70 randomly very quickly.

raw values looks like this:

Any1 had similar experience or have any tips what am I doing wrong?

With code:

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

void loop() {
  int sensorValue = analogRead(A5);
  Serial.println(sensorValue);
  delay(200);        
}

0 0 0 0 0 0 0 0 2 6 8 10 14 17 20 23 25 29 32 35 36 41 42 46 49 52 55 57 60 60 62 62 62 61 60 60 57 57 56 56 55 55 53 53 52 49 46 42 38 35 31 28 24 22 18 15 11 8 7 0 0 0 0 0 0 0 another output -_- — Tomáš John

Vladimir Tsykunov Vladimir Tsykunov · Accepted Answer · 2016-03-31T07:14:32

Seems you code is ok. But try to use another pin, A0. Because A5 is sharing I2C interface and this may be the issue. Also:

try to use decoupling capacitor 0.1 uF close to the sensor.
you can do a simple check if the sensor is in good condition. Replace the sensor with voltage source with known output. Measure if output of adc function returns valid results.
look at sensors output using osciliscope or multimeter. If it has voltage drops to zero or not.

I also suppose that you may be measuring voltage splashes at 50Hz (60 for US) that are common for usb.

Arduino Nano incorrect analogReading values

1 Answers