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Topic: TMP36 unusual readings (Read 70 times) previous topic - next topic


So I am doing the Arduino sketch involving the "love meter" and decided that having a set baseline is silly if you find yourself in a hotter (or colder) environment that you set up in. I decided to program the sensor to set its baseline up for 5 seconds at the beginning before doing the readout. The programing seemed to work, but my sensor goes off the rails when I pinch it to increase the temp showing temps as high as 60 C (140 F) and it won't decrease past 40 C (104 F) any thoughts on this? I'll include my code below for all who are interested.

const int sensorPin = A0;
float baselineTemp = 0.0;
float currentset = 0.0;

void setup() {
  // put your setup code here, to run once:
  for(int pinNumber = 2; pinNumber <5; pinNumber++){
    pinMode(pinNumber, OUTPUT);
    digitalWrite(pinNumber, LOW);
  while(millis() < 5000) {
    // currentset is being turned into sensor value
    currentset = analogRead(sensorPin);
    // currentset is being turned into voltage
    currentset = (currentset/1024.0) * 5.0;
    // currentset is being turned into temp in C
    currentset = (currentset - .5) * 100;
    if( currentset > baselineTemp) {
      baselineTemp = currentset;

void loop() {
  // put your main code here, to run repeatedly:
  int sensorVal = analogRead(sensorPin);
  Serial.print("Sensor Value: ");
  float voltage = (sensorVal/1024.0) * 5.0;
  Serial.print(", Volts: ");
  Serial.print(", degrees C: ");
  float temperature = (voltage - .5) * 100;
  if(temperature < baselineTemp+2){
    digitalWrite(2, LOW);
    digitalWrite(3, LOW);
    digitalWrite(4, LOW);
   }else if(temperature >= baselineTemp+2 && temperature < baselineTemp+4){
    digitalWrite(2, HIGH);
    digitalWrite(3, LOW);
    digitalWrite(4, LOW);
   } else if(temperature >= baselineTemp+4 && temperature < baselineTemp+6){
    digitalWrite(2, HIGH);
    digitalWrite(3, HIGH);
    digitalWrite(4, LOW);
   }else if(temperature >= baselineTemp+6){
    digitalWrite(2, HIGH);
    digitalWrite(3, HIGH);
    digitalWrite(4, HIGH);
    digitalWrite(4, LOW);


What have you done to try to figure out the reason for the problem (such as other tests, internet research, etc)?


Sep 25, 2016, 01:54 am Last Edit: Sep 25, 2016, 02:11 am by Wawa
Usually a wiring problem.
The TMP36 works better if ground is directly connected to a ground pin of the Arduino.
Not via a breadboard with other devices/LEDs that use the same ground.
3.3volt supply might also be cleaner than a 5volt supply.

Use this sketch for testing.
Code: [Select]
// TMP36 temp

void setup() {
  analogReference(INTERNAL); // use 1.1volt bandgap Aref

void loop() {
  Serial.println((analogRead(A0) * 0.1039) - 50.0, 1);

Your code prints everything on one line.
Use Serial.println, so the next item will be printed on the next line.


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