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Micropython Generic Thermistor Library

Micropython Generic Thermistor Library is a basic software module designed to simplify temperature sensing using NTC thermistors within MicroPython-based projects. The library assumes a generic NTC thermistor on the ground side of a voltage divider. It provides functions for converting raw analog sensor readings into temperature values, taking into account the non-linear nature of thermistors using the β parameter equation.

Features

• Temperature output in Kelvin, Celsius, or Fahrenheit
• Checks for thermistor shorts to VCC or GND
• Checks for reasonable output values as specified in Constants
• New thermistors only require one line of code!

Installation - Hardware

Figure 1 demonstrates the expected wiring scheme. R1 and the thermistor cannot be swapped with this library; the code assumes the thermistor is on the ground side of the voltage divider.

Notes:

• The resistance of R1 should be similar to the nominal resistance of the thermistor
• Thermistor nominal resistance and beta values can be found on the thermistor datasheet
• Thermistor is assumed to be NTC

Installation - Software

1. Have a Micropython environment set up on something; for example, an ESP32
2. Upload the thermistor.py file onto the Micropython device; upload steps vary based on familiarity with the terminal, OS, and/or IDE. You can create a new file named thermistor.py on the embedded device and copy-paste the code into the file.
3. Configure the object constructor "Thermistor" with your values. The below example uses pin 4 on an ESP32 with a 10k ohm NTC, beta=3435, thermistor, and 10k ohm voltage divider. Make sure you use your own values here!

therm = Thermistor(ADC(4, atten=ADC.ATTN_11DB), beta=3435, therm_ohm=10_000, divider_ohm=10_000)

4. See the example main.py file

Warnings

• This code was only tested on a single ESP32, with a single version of Micropython. Your mileage may vary.
• This code does not have thermal runaway protection; use heating devices at your own risk.