# [3/Love-o-meter] it seems TMP36 doesn't work (volts: 0.00 ; degrees: -50.00)

hiduino:

kukulo: I implemented project 03 (love-o-meter) but the value measured by the sensor varies between 144 and 146, that means 0 volts and a temperature of -50.00 degrees.

The formula for the voltage should be;

Voltage = (sensor / 1024) X 5.0

So if you had a sensor value of 145 then it should be (145/1024) X 5 = 0.71 volts, not 0 volts.

Thank you, hiduino! Do you know what? I calculated Voltage by multiplying to 0.5 instead of 5.0 :blush: Adjusting the multiplication factor, it works fine.

Just a short note: if I write "Voltage = (sensor /1024) * 5.0", Voltage is calculated as 0.00; instead, if I write "Voltage = (sensor /1024.0) * 5.0", the result is correct (not zero). Do I need to write any number using at least a decimal place after point? But this is not really a problem for me: probably, a better knowledge of this specific coding language could help me in avoiding this kind of mistakes.

There are rules how the compiler handles math operators. If both are int the result will be int. That is why sensor/1024 = 0; and sensor/1024.0 = >0;

Furthermore from performance point of view it is always faster to multiply than to divide e.g.

x/10.0 is slower than x * 0.1;

Garmien:

hiduino:

Garmien: Any idea what i'm doing wrong?

Should be the same as in the manual.

``````const int sensorPin = A0;
const float baselineTemp = 20.0;
``````

void setup(){  Serial.begin(9600);  for(int pinNumber = 2; pinNumber < 5; pinNumber++){    pinMode(pinNumber, OUTPUT);    digitalWrite(pinNumber, LOW);  } }

void loop(){  int sensorVal = analogRead(sensorPin);  Serial.print("Sensor Value: ");  Serial.print(sensorVal);  float voltage = (sensorVal/1024.0)*5.0;  Serial.print(", Volts: ");  Serial.print(voltage);  Serial.print(", Degrees: ");  float temperature = (voltage - .5)*100;  Serial.println(temperature);    if(temperature < baselineTemp){    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);  }  delay(100); }

I just realised i had made some changes, so the numbers are different (but still not correct). This is the true outprint example with the above code:

Sensor Value: 52, Volts: 0.25, Degrees: -24.61 Sensor Value: 53, Volts: 0.26, Degrees: -24.12 Sensor Value: 56, Volts: 0.27, Degrees: -22.66 Sensor Value: 61, Volts: 0.30, Degrees: -20.21 Sensor Value: 69, Volts: 0.34, Degrees: -16.31 Sensor Value: 74, Volts: 0.36, Degrees: -13.87 Sensor Value: 75, Volts: 0.37, Degrees: -13.38 Sensor Value: 73, Volts: 0.36, Degrees: -14.36 Sensor Value: 68, Volts: 0.33, Degrees: -16.80 Sensor Value: 58, Volts: 0.28, Degrees: -21.68 Sensor Value: 56, Volts: 0.27, Degrees: -22.66 Sensor Value: 53, Volts: 0.26, Degrees: -24.12 Sensor Value: 52, Volts: 0.25, Degrees: -24.61

Garmien: I just realised i had made some changes, so the numbers are different (but still not correct). This is the true outprint example with the above code:

Sensor Value: 52, Volts: 0.25, Degrees: -24.61 Sensor Value: 53, Volts: 0.26, Degrees: -24.12 Sensor Value: 56, Volts: 0.27, Degrees: -22.66 Sensor Value: 61, Volts: 0.30, Degrees: -20.21 Sensor Value: 69, Volts: 0.34, Degrees: -16.31 Sensor Value: 74, Volts: 0.36, Degrees: -13.87 Sensor Value: 75, Volts: 0.37, Degrees: -13.38 Sensor Value: 73, Volts: 0.36, Degrees: -14.36 Sensor Value: 68, Volts: 0.33, Degrees: -16.80 Sensor Value: 58, Volts: 0.28, Degrees: -21.68 Sensor Value: 56, Volts: 0.27, Degrees: -22.66 Sensor Value: 53, Volts: 0.26, Degrees: -24.12 Sensor Value: 52, Volts: 0.25, Degrees: -24.61

Looks like your sensor acts more like a TMP 35 range. If you remove the - .5 from the formula (temperature = voltage * 100) do the readings make sense? Are the sensor values changing that fast? It could be bad connections causing sporadic readings. Otherwise I guess it could be just a bad sensor.

My sensor doesn't seem to work either. I get these values: Sensor value: 26, Volts: 0.13, degrees C: -37.30 Sensor value: 25, Volts: 0.12, degrees C: -37.79 I have the same code as in the manual, and connected everything like the manual too. If i use 3.3V instead of 5V i get: Sensor value: 34, Volts: 0.17, degrees C: -33.40 Sensor value: 34, Volts: 0.17, degrees C: -33.40

hiduino:

Garmien: I just realised i had made some changes, so the numbers are different (but still not correct). This is the true outprint example with the above code:

Sensor Value: 52, Volts: 0.25, Degrees: -24.61 Sensor Value: 53, Volts: 0.26, Degrees: -24.12 Sensor Value: 56, Volts: 0.27, Degrees: -22.66 Sensor Value: 61, Volts: 0.30, Degrees: -20.21 Sensor Value: 69, Volts: 0.34, Degrees: -16.31 Sensor Value: 74, Volts: 0.36, Degrees: -13.87 Sensor Value: 75, Volts: 0.37, Degrees: -13.38 Sensor Value: 73, Volts: 0.36, Degrees: -14.36 Sensor Value: 68, Volts: 0.33, Degrees: -16.80 Sensor Value: 58, Volts: 0.28, Degrees: -21.68 Sensor Value: 56, Volts: 0.27, Degrees: -22.66 Sensor Value: 53, Volts: 0.26, Degrees: -24.12 Sensor Value: 52, Volts: 0.25, Degrees: -24.61

Looks like your sensor acts more like a TMP 35 range. If you remove the - .5 from the formula (temperature = voltage * 100) do the readings make sense? Are the sensor values changing that fast? It could be bad connections causing sporadic readings. Otherwise I guess it could be just a bad sensor.

Above print is with 100ms delay. Also, the sensor does not react on temperature changes at all. I've tried with different sensors of the same type, the result is the same (print below is without the -.5):

Sensor Value: 55, Volts: 0.27, Degrees: 26.86 Sensor Value: 55, Volts: 0.27, Degrees: 26.86 Sensor Value: 56, Volts: 0.27, Degrees: 27.34 Sensor Value: 57, Volts: 0.28, Degrees: 27.83 Sensor Value: 60, Volts: 0.29, Degrees: 29.30 Sensor Value: 67, Volts: 0.33, Degrees: 32.71 Sensor Value: 72, Volts: 0.35, Degrees: 35.16 Sensor Value: 75, Volts: 0.37, Degrees: 36.62 Sensor Value: 75, Volts: 0.37, Degrees: 36.62 Sensor Value: 70, Volts: 0.34, Degrees: 34.18 Sensor Value: 64, Volts: 0.31, Degrees: 31.25 Sensor Value: 59, Volts: 0.29, Degrees: 28.81 Sensor Value: 57, Volts: 0.28, Degrees: 27.83 Sensor Value: 56, Volts: 0.27, Degrees: 27.34 Sensor Value: 55, Volts: 0.27, Degrees: 26.86 Sensor Value: 55, Volts: 0.27, Degrees: 26.86

EDIT: Something is very wrong, if i change the sensors position on the breadboard i get different values..

Garmien: EDIT: Something is very wrong, if i change the sensors position on the breadboard i get different values..

It might be that the Arduino input port is bad? Can you try changing to another analog input port? (make sure you update your code to match) Also some times if the wire leads are too long they can affect the sensor measurements.

hiduino:

Garmien: EDIT: Something is very wrong, if i change the sensors position on the breadboard i get different values..

It might be that the Arduino input port is bad? Can you try changing to another analog input port? (make sure you update your code to match) Also some times if the wire leads are too long they can affect the sensor measurements.

I tried some of the other projects before going back to this, now i get these numbers(again with 100ms delay):

Sensor Value: 0, Volts: 0.00, Degrees: -50.00 Sensor Value: 0, Volts: 0.00, Degrees: -50.00 Sensor Value: 0, Volts: 0.00, Degrees: -50.00 Sensor Value: 0, Volts: 0.00, Degrees: -50.00 Sensor Value: 0, Volts: 0.00, Degrees: -50.00 Sensor Value: 35, Volts: 0.17, Degrees: -32.91 Sensor Value: 92, Volts: 0.45, Degrees: -5.08 Sensor Value: 96, Volts: 0.47, Degrees: -3.13 Sensor Value: 97, Volts: 0.47, Degrees: -2.64 Sensor Value: 89, Volts: 0.43, Degrees: -6.54 Sensor Value: 74, Volts: 0.36, Degrees: -13.87 Sensor Value: 0, Volts: 0.00, Degrees: -50.00 Sensor Value: 0, Volts: 0.00, Degrees: -50.00 Sensor Value: 0, Volts: 0.00, Degrees: -50.00 Sensor Value: 0, Volts: 0.00, Degrees: -50.00 Sensor Value: 0, Volts: 0.00, Degrees: -50.00

with this code:

``````const int sensorPin = A0;
const float baselineTemp = 20.0;

void setup(){
Serial.begin(9600);
for(int pinNumber = 2; pinNumber < 5; pinNumber++){
pinMode(pinNumber, OUTPUT);
digitalWrite(pinNumber, LOW);
}
}

void loop(){
Serial.print("Sensor Value: ");
Serial.print(sensorVal);
float voltage = (sensorVal/1024.0)*5.0;
Serial.print(", Volts: ");
Serial.print(voltage);
Serial.print(", Degrees: ");
float temperature = (voltage - .5)*100;
Serial.println(temperature);

if(temperature < baselineTemp){
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);
}
delay(100);
}
``````

I've noticed the numbers are the same whether i have the + connected or not, so i guess there's something wrong with the power? Or the sensor(s)?

hello I tested the tmp36 and I think I will not use again! the tmp36 is too sensitive to electrostatic waves. the only way I managed it by adding a 0.1 uf ceramic capacitor for the values ??are more stable on the breadboard. but when you make a perforated plate or you use more than one tmp36 or otherwise in a surrounding with lots of electrostatic waves (film studio, or near a motor). this is not the same games. the first tmp36 influences the values ??of the other and so on. Environmental electrostatic waves distort the sensor values

The slightest change of voltage (power outage, run down, connection error etc.). Sensor burns. must be experienced in electronics, it's really not recommended to beginners! it should be noted that on this forum there are requests for help almost every 2 days for tmp36. must deduce something. I finally used a thermistor (variable resistor heat) and everything is settled.

emmanuelle

Double check that you are using the correct componant. I made the mistake of using the wrong componant.

Yes the Transistor looks similar to the Temperature Sensor. They have the same black body with 3 legs though the Transistor outer legs are bent whereas the Temp Sensor I have the legs are all straight.

Anyway I tried a transistor in the circuit and got varying negative readings like those in this thread.

So ensure it's really the Temperature Sensor and not one of the Transistors. In my official kit I got 1X Temp Sensor and 5X Transistors which were taped to a card.

for project love-o-meter This is my code, its from the book, and when I compile it works without errors, when I connected Arduino to it, only the LED that was connected to pin 3 came on, nothing else happened, nothing on the serial monitor, what am I doing wrong

const int sensorPin = A0; const float baselineTemp = 20.0; void setup(){ Serial.begin(9600); for(int pinNumber=2; pinNumber<5; pinNumber++){ pinMode(pinNumber,OUTPUT); digitalWrite(pinNumber, LOW); } } void loop (){ int sensorVal=analogRead(sensorPin); Serial.print("Sensor Value: "); Serial.print(sensorVal); float voltage=(sensorVal/1024.0)* 5.0; Serial.print(",Volts:"); Serial.print(voltage); Serial.print(",degrees C:"); float temperature=(voltage-.5)*100; Serial.println(temperature); 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); } delay(1); }

As @arucarn posted, make sure you are using the correct component. The TMP36 temperature sensor looks almost identical to the BC 547B transistor.

If you have the Arduino starter kit then you will most likely have 5 transistors but only 1 temperature sensor.

The temperature sensor has entirely straight legs where as the transistor has straight legs that pinch in at the top.

I don't know if this will help anyone but just in case... I was having similar problems to those listed above with negative reads on my sensor. I checked and double checked the circuit and the code. I was about to give up when I realized it was way hotter in this room than my defined baseline temp, and hotter my max baseline temp +. I changed my baseline to match the actual temp in the room (almost 80 degrees) and it worked.

I have the same problem. Wired correctly, using the code from the site. Normal reading are in the -40s or -50s.

I bought a couple more temperature sensors from the site so I'll try them when I get them.

I was having the same problem with the negative numbers. Turned out I just took the wrong part from the starter kit. Make sure you have the temperature sensor...

Hi there

I've played with this sample and the tmp36 sensor. No problem so far , it was quite straightforward.

Only concern is that sensor output is not really stable, i get this serial output: sensor Value: 146, Volts: 0.71, degrees C: 21.29 sensor Value: 144, Volts: 0.70, degrees C: 20.31 sensor Value: 145, Volts: 0.71, degrees C: 20.80 sensor Value: 144, Volts: 0.70, degrees C: 20.31 sensor Value: 144, Volts: 0.70, degrees C: 20.31 sensor Value: 147, Volts: 0.72, degrees C: 21.78 sensor Value: 144, Volts: 0.70, degrees C: 20.31 sensor Value: 146, Volts: 0.71, degrees C: 21.29 sensor Value: 144, Volts: 0.70, degrees C: 20.31

So my questions are: - is it normal, and is it the correct behaviour of this sensor? - if I want to improve the accuracy, should i change the sensor, the wiring, or focus on the software, with maybe a moving mean?

I've already faced this kind of analogic issue, with a capacitive sensor, and i used a moving mean. It was not really suitable for my purpose because it was for an input device, so adding latency with the computation of the mean was not good.

I'm interested in any suggestion, and quite a newb in electronics. Thanks for reading

Nico

The problem with the negative value will be solved with the answer of Simo_xx: Just use the temperature sensor and not one of the 5 transistors! VERY USEFUL. Thanks Simo_xx. Problem solved :)

Hi everyone,

I ran into a problem where my code has uploaded and everything seems to be connected but instead of lighting up after i touch the sensor. Once i plug in the power source all the LEDs are already lit.

I am not sure what happened here

Small chance this will help someone, in my case it was a goof in the code, mis-wrapped my parens:

wrote: float temperature = (voltage - .5 * 100);

instead of: float temperature = (voltage - .5) * 100;

Just one of those moments (thus a reminder), so make sure you spend some time on the obvious sources of problems if you hit this, particularly if you are seeing a lot of the ~-49C readings.