Electronic – arduino – Excessively high temperature reading with LM35

arduinovoltage

I am really new to electronics and I am just experimenting at the moment with a breadboard.

My question here is related to the LM35 temperature sensor and Arduino micro controller. I am getting a very high reading through the sensor of 448 degrees Celsius. Obviously this is way off. The conversion formula I am using is:

inputvoltage = (5.0*inputvoltage*100.0)/1024.0;

I am feeding 5V into the sensor from the Arduino and I am getting a 0.50 voltage reading on my multimeter between 5V in and output. Do you think the sensor might be faulty? Any help on this issue would be great!

EDIT: Some people have asked for my code from the arduino so here it is:

int tempPin = 0;

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

void loop() {
  float temp = (5.0 * analogRead(tempPin) * 100.0) / 1024;
  Serial.print(temp,1);
  Serial.println(" degrees C   ");
  delay(1000);
  }

enter image description here This schematic shows the really simple configuration I have.

enter image description here

I have added a picture of my setup if anybody can spot something I can't.

Best Answer

4.15V from Vout to GND with short wires and 5V supply is totally wrong. Either you have the connections wrong or the LM35 is toast. Please double-check the connection vs. the datasheet.

I suspect just because of that particular voltage reading that you may have the connections mixed up.

Edit: Thanks for the photo. Looking at the part from the front (the part with the markings) from left to right, the pin order is:

enter image description here

Vs, Vout, GND = +5, Vout, GND

In your photo I see +5, Vout, GND as it should be. So it it's reading more than 10mV/°C at Vout with the blue wire disconnected from the Arduino (and 5V/0V on the orange and black wires respectively) I would say it's dead. Perhaps the power got momentarily reversed on it?

Related Topic