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Ligne 30 : − + − {{traduction}}+ − Comment calculer la température Il faut donc convertir la tension analogique en degré. Comme le TMP36 permet de mesurer des température négatives, le 0 degré Celsius est placé à une offset de 500 milliVolts. Ainsi, toute mesure inférieur à 500 mv correspondra à une température négative. − La formule est la suivante pour le TMP36:+ − + − Donc, si la tension de sortie est de 1 Volts, la température correspondante est de+ − − Soit 50 degrés Celcius.+ − si vous utilisez un LM35 ou similaire, la température se calcule comme suit (utiliser la ligne 'a' sur le graphique):+ − Temp en °C = ( Tension_de_sortie_en_millivolts) / 10 + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + − + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + − Pour l'utiliser, connectez simplement la broche 1 (gauche) à une source d'alimentation (entre 2.7 et 5.5V), la broche 3 (droite) à la masse (gnd) et finalement la broche 2 (au milieu) sur une entrée analogique de votre microcontroleur.+ + + + + + + + + + − La tension de sortie est de 0V à -50°C et 1.75V à 125°C. Il est facile de convertir la tension de sortie (en millivolts) en température à l'aide de la formule:+ − Temp °C = 100*(lecture en V) - 50+ − La fiche technique du TMP36 est accessible ici.+ +
→High resolution reading
* [http://www.analog.com/en/mems-sensors/digital-temperature-sensors/tmp36/products/product.html TMP36 datasheet] (''analog.com'', html)
* [http://www.analog.com/en/mems-sensors/digital-temperature-sensors/tmp36/products/product.html TMP36 datasheet] (''analog.com'', html)
=== how to measure the temperature ===
=== How to measure the temperature ===
It will be necessary to convert the analogue voltage intro degree. As the TMP36 can also measure negative temperature, the 0 degree Celcius is placed at 500 mV offset. So, any voltage under 0.5 Volt is a negative temperature.
[[Fichier:TMP36-Graph.png]]
[[Fichier:TMP36-Graph.png]]
Here is the formula to use with a TMP36 powered at 3.3v:
Temp en °C = ( Tension_de_sortie_en_milliVolts - 500) / 10
Temp in °C = ( output_voltage_in_mV - 500) / 10
So, if we do have an output voltage of exactly 1 Volt (1000 mV) then the temperature would be
(1000 - 500)/10
temp = (1000 - 500)/10
So 50 Celcius degrees.
== Wiring ==
To use the TMP36, connect:
* The pin 1 (on the left) to a power source (3.3V),
* The pin 3 (the the right droite) to the ground/GND.
* The pin 2 (middle one) to the A3 analogue input.
[[Fichier:ENG-CANSAT-TMP36-01.png|480px]]
The TMP36 output voltage would range from 0V @ -50°C to 1.75V @ 125°C. So no risk for our 3V based microcontroler.
== Testing the sensor ==
In the both case show here under, the measured temperature would be identical.
{{ambox|text=However, if your project does need a high resolution analog reads then it may be appropriate to explore the "High Resolution Reading" example.}}
By default, the Arduino's {{fname|analogRead()}} use a 10 bit coding. So the range of possible value return by {{fname|analogRead()}} is 0 to 1024 (for 0 to 3.3v). This means that the accuracy of reading is 3.3 / 1024 = 0.0032 Volts, so 3.2 mV.
As the M0 does have an ADC (''Analog-to-Digital Converter'') with a precision of 12 bits, we could also use the {{fname|analogReadResolution( 12 )}} to upgrade the {{fname|analogRead()}} resolution to 12 bits. In such case, the range of possible value return by {{fname|analogRead()}} is 0 to 4095 (for 0 to 3.3v). As we have a real 12bit ADC, we can rely on that accuracy (it is not a 10 bits ADC storing the data into a 12 bits integer).
with 12bits we have an reading accuracy of 3.3 / 4095 = 0.000805 Volts, so 0.805 mV.
=== Low resolution reading ===
<syntaxhighlight lang="c">
// where is wired the TMP36
const int temperaturePin = A3; // analogue input
// Executed once when starting the microcontroler
void setup() {
// start serial connexion with the computer
Serial.begin(9600);
}
// Executed again and again
void loop() {
// read the voltage of TMP36
float voltage = getVoltage(temperaturePin);
Serial.print( "Voltage : " );
Serial.print( voltage );
Serial.println( " Volts" );
// convert voltage to temperature
// Degrees = (voltage - 500mV) multiplied by 100
float temperature = (voltage - .5) *100;
Serial.print( "Temperature: " );
Serial.print(temperature);
Serial.println( " °C" );
Serial.println( " " );
delay(1000); // wait 1 second
}
/*
* getVoltage() - return the voltage of an analog pin
*/
float getVoltage(int pin){
// AS the sketch does not call the analogReadResolution()
// function to change the analog reading resolution
// THEN Arduino use the defaut 12 bits resolution!
// Under 12 bits resolution, the analogRead() returns
// a value between 0 & 1024.
//
// Convert digital value between 0 & 1024 to
// voltage between 0 & 3.3 volts.
// (each unit equal 3.3 / 1024 = 3.2 millivolts)
return (analogRead(pin) * .0032);
}
</syntaxhighlight>
Once the sketch uploaded to the board, you can start the Serial Monitor
[[Fichier:ENG-CANSAT-BMP280-04.png]]
Which produce the following result on the Serial Monitor
[[Fichier:ENG-CANSAT-TMP36-60.png|640px]]
{{ENG-CANSAT-TRAILER}}
== Wiring ==
=== High resolution reading ===
<syntaxhighlight lang="c">
// where is wired the TMP36
const int temperaturePin = A3; // analogue input
// Executed once when starting the microcontroler
void setup() {
// start serial connexion with the computer
Serial.begin(9600);
// Upgrade the ADC resolution from 10 to 12 bits.
analogReadResolution( 12 );
}
// Executed again and again
void loop() {
// read the voltage of TMP36
float voltage = getVoltage(temperaturePin);
Serial.print( "Voltage : " );
Serial.print( voltage );
Serial.println( " Volts" );
// convert voltage to temperature
// Degrees = (voltage - 500mV) multiplied by 100
float temperature = (voltage - .5) *100;
Serial.print( "Temperature: " );
Serial.print(temperature);
Serial.println( " °C" );
Serial.println( " " );
delay(1000); // wait 1 second
}
/*
* getVoltage() - return the voltage of an analog pin
*/
float getVoltage(int pin){
// Convert digital value between 0 & 4095 to
// voltage between 0 & 3.3 volts.
// (each unit equal 3.3 / 4095 = 0.805 millivolts)
return (analogRead(pin) * .000805);
}
</syntaxhighlight>
Once the sketch uploaded to the board, you can start the Serial Monitor
[[Fichier:ENG-CANSAT-BMP280-04.png]]
Which produce the following result on the Serial Monitor
[[Fichier:ENG-CANSAT-TMP36-70.png|640px]]
{{ENG-CANSAT-TRAILER}}
{{ENG-CANSAT-TRAILER}}