(Reference) TMP36

TMP36 Analog Temperature Sensor

Wiring

Requires analog input pin

• A0
• A1
• A2
• A5
• A3 (SDA or D0)
• A4 (SCL or D1)

Orientation

• Note that is BOTTOM VIEW

Operation

• Analog temperature sensor
• Measures environment temperature and returns a voltage
• Since this is an analog input, we use analog to digital conversion to read input
• Voltage on pin will varies 0v to 3.v, and Photon 2 will read 0 to 4095

Conversions

• 10 mV per deg C with a 0.5 v offset
• voltage = ADC_val / 4095 * 3.3
• tempCelsius = (voltage - 0.5) * (1 / 0.01)
• tempFahrenheit = tempCelsius * (9/5) + 32

Important: C++ int and float

• Division with ints in C++ truncates decimals

int x = 3;
int y = 6;
float result = x / y; // 0 since 3/6 is truncated` 

• Instead, make sure to cast (convert) one of the int values to be a float

int x = 3;
int y = 6;
float result = (float) x / y;

​

Code

const int PIN_TMP = A5;

void setup() {
    Serial.begin(9600);
    pinMode(PIN_TMP, INPUT);
}

void loop() {
    // read ADC value
    int val = analogRead(pin_temp);  // range 0-4095 ADC
    
    // calculate voltage from ADC
    float voltage = (float)val / 4095 * 3.3;
    
    // calculate celsius from voltage
    float tempC = (voltage - 0.5) / 0.01;
    
    //convert to fahrenheit
    float tempF = tempC * (9.0 / 5) + 32;
}

Credit

• Analog datasheet
• Sparkfun
• Images created with Fritzing