temp reader for array (thermistor and arduino)

[jana-daouk]

No description provided.

[gemini-code-assist]

Summary of Changes

Hello @jana-daouk, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a new Arduino sketch that enables temperature measurement using a thermistor. It provides a foundational example for integrating analog temperature sensors with an Arduino board, performing necessary calculations to convert raw sensor data into human-readable temperature units, and outputting them via serial communication.

Highlights

• New Arduino Sketch for Thermistor Reading: Introduces ArduinoTemp.ino, a new sketch designed to interface with a thermistor, read analog values, and convert them into temperature readings in both Celsius and Fahrenheit.
• Steinhart-Hart Equation Implementation: The sketch includes the implementation of the Steinhart-Hart equation, a common method for accurately converting thermistor resistance to temperature in Kelvin, which is then converted to Celsius and Fahrenheit.
• Serial Output for Monitoring: The program outputs raw Analog-to-Digital Converter (ADC) readings, calculated voltage, and the final temperature values to the serial monitor, allowing for easy debugging and monitoring.

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Changelog

• arduino/ArduinoTemp.ino
  • Added a new Arduino sketch (.ino file) for reading temperature from a thermistor.
  • Includes setup for serial communication at 9600 baud.
  • Implements the Steinhart-Hart equation to convert thermistor resistance to Kelvin, then to Celsius and Fahrenheit.
  • Outputs raw ADC values, voltage, and calculated temperatures to the serial monitor every 500 milliseconds.

Activity

• No specific activity (comments, reviews, or progress updates) has been recorded for this pull request yet.

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[gemini-code-assist]

Code Review

This pull request adds an Arduino sketch for reading temperature from a thermistor. The code is a good starting point, but there are several areas for improvement. I've identified a critical issue regarding a potential division-by-zero error and an inconsistency between a comment and the code logic. I've also suggested several improvements for maintainability and readability, such as using constants for fixed values, scoping variables correctly, and a minor optimization for the temperature calculation. Addressing these points will make the code more robust and easier to maintain.

[gemini-code-assist]

There are two issues here:

1. Inconsistent Comment: The comment on line 33 describes a circuit (5V -> R1 -> A0 -> thermistor -> GND) that is inconsistent with the formula on line 34. The formula R2 = R1 * (1023.0 / (float)Vo - 1.0) is for a circuit where the thermistor and fixed resistor are swapped (5V -> thermistor -> A0 -> R1 -> GND). This should be corrected to avoid confusion.

2. Division by Zero: If Vo is 0 (which can happen if the thermistor circuit is open), the formula on line 34 will cause a division-by-zero error, leading to inf values in subsequent calculations. It's critical to handle this edge case to prevent undefined behavior and provide meaningful feedback.

Here is a suggested fix that corrects the comment and adds a safety check:

Suggested change

	// Assumes: 5V -> R1 -> A0 -> thermistor -> GND
	R2 = R1 * (1023.0 / (float)Vo - 1.0);
	// Assumes: 5V -> thermistor -> A0 -> R1 -> GND
	if (Vo < 1) {
	Serial.println("Error: Thermistor open circuit?");
	delay(500); // Prevent spamming serial output
	return; // Skip the rest of the loop
	}
	R2 = R1 * (1023.0 / (float)Vo - 1.0);

[gemini-code-assist]

For pin definitions, it's better to use const to prevent accidental changes. Also, for analog pins, it's idiomatic in Arduino to use the A0, A1, etc. aliases for better readability and portability across different Arduino boards.

Suggested change

	int ThermistorPin = 0;
	const int ThermistorPin = A0;

[gemini-code-assist]

The variables Vo, logR2, R2, T, Tc, and Tf are declared as global but are only used within the loop() function. It's a good practice to limit the scope of variables to where they are needed. Please move their declarations inside the loop() function. This makes the code cleaner, easier to reason about, and prevents potential unintended side effects.

For example:

void loop() {
  int Vo;
  float logR2, R2;
  float T, Tc, Tf;

  // ... rest of the loop code
}

[gemini-code-assist]

The resistor value is a constant and should be declared with const to prevent accidental modification. It's also good practice to define floating-point constants with a decimal point to make their type clear.

Suggested change

	float R1 = 10000;
	const float R1 = 10000.0;

[gemini-code-assist]

The Steinhart-Hart coefficients are constants and should be declared with const to prevent accidental modification at runtime.

Suggested change

	float c1 = 1.009249522e-03;
	float c2 = 2.378405444e-04;
	float c3 = 2.019202697e-07;
	const float c1 = 1.009249522e-03;
	const float c2 = 2.378405444e-04;
	const float c3 = 2.019202697e-07;

[gemini-code-assist]

The calculation of the Steinhart-Hart equation can be made slightly more efficient and arguably more readable by factoring out logR2, similar to using Horner's method for polynomial evaluation. This reduces the number of multiplications.

Suggested change

	T = 1.0 / (c1 + c2 * logR2 + c3 * logR2 * logR2 * logR2);
	T = 1.0 / (c1 + logR2 * (c2 + c3 * logR2 * logR2));