NTC sensor – RPI Pico

Table of Contents

NTC Readout (micropython)
Products
Source

NTC Readout (micropython) #

We wire the circuit on the Breadboard and connect it to the Raspberry Pi Pico device.

In the MicroPython code we need to do the following steps:

We measure Vout using the ADC on Raspberry Pi Pico
We calculate Rt using the Voltagee Divider Equation
Then we use Steinhart-Hart equation for finding the Temperature
Finally we convert from degrees Kelvin to Celsius

MicroPython Code Eeample for reading and calculation the Temperature Value from a Thermistor:

from machine import ADC
from time import sleep
import math

adcpin = 28
thermistor = ADC(adcpin)

# Voltage Divider
Vin = 3.3
Ro = 10000  # 10k Resistor

# Steinhart Constants
A = 0.001129148
B = 0.000234125
C = 0.0000000876741

while True:
    # Get Voltage value from ADC   
    adc = thermistor.read_u16() >> 4 # Get original 12-bit value 0-4096
    print ("ADC Value:", adc)
    Vout = (3.3/4096) * adc
    
    # Calculate Resistance
    Rt = (Vout * Ro) / (Vin - Vout) 
    #Rt = 10000  # Used for Testing. Setting Rt=10k should give TempC=25
    
    # Steinhart - Hart Equation
    TempK = 1 / (A + (B * math.log(Rt)) + C * math.pow(math.log(Rt), 3))

    # Convert from Kelvin to Celsius
    TempC = TempK - 273.15
    
    #Correction for %5
    TempC = TempC - 7

    print(round(TempC, 1))
    sleep(1)