Decoding Coolant Temp Sensor Code for Arduino: A DIY Guide

Automotive sensors are increasingly popular in DIY electronics projects, especially with platforms like Arduino. Among these, the coolant temperature sensor is a useful component for monitoring engine health or various temperature-sensitive systems. This guide focuses on utilizing a widely available General Motors (GM) coolant temperature sensor, part number 12146312, with your Arduino. We’ll break down the wiring, the necessary components, and most importantly, the Coolant Temp Sensor Code to get accurate temperature readings.

Understanding how to read a coolant temperature sensor is crucial for various automotive projects. These sensors are designed to measure the temperature of the engine coolant, providing critical data to the vehicle’s computer system to regulate engine performance and prevent overheating. By interfacing this sensor with an Arduino, you can create custom digital dashboards, temperature monitoring systems, or even integrate it into more complex DIY automotive control systems.

For this project, we’ll be using the GM coolant sensor part #12146312. This sensor is robust, readily available, and designed for automotive environments. It’s a two-wire sensor that operates on a 5V system, making it compatible with Arduino’s voltage levels. The datasheet for this sensor, including the mating connector details, can be found at DELPHI COOLANT TEMPERATURE SENSOR PART NUMBER 12146312.

To interface this sensor with your Arduino Uno, you’ll need a couple of resistors in addition to the sensor itself. After some experimentation and calculations based on the sensor’s operating range, a combination of a 2.2K ohm resistor and a 550 ohm resistor in series has proven effective.

Here’s how to wire the GM coolant temperature sensor to your Arduino:

• The sensor has two wires. One wire needs to be connected to the ground of your Arduino.
• The other wire is the data wire. This wire connects to the Arduino’s 5V supply through the series of resistors (2.2K ohm and 550 ohm). Specifically, the resistors are placed in series between the Arduino’s 5V pin and the sensor’s data wire. The point where the two resistors connect then goes to the sensor’s signal wire, and the other end of the resistor chain connects to the 5V pin on the Arduino.
• For reading the sensor data, the data wire (the one connected to the resistors and sensor) is also connected to Analog pin 0 on the Arduino. You can use any analog pin from A0 to A5 on your Arduino Uno, just make sure to adjust the code accordingly.

Below is a diagram illustrating the wiring setup for the GM coolant temperature sensor (part #12146312) with Arduino.

GM Coolant Temperature Sensor Wiring Diagram for Arduino using Part Number 12146312 and Resistors

Now, let’s look at the Arduino code required to read the coolant temperature sensor data and convert it into a readable temperature value. This code is designed for the GM coolant sensor 12146312 and outputs the temperature in Fahrenheit via the serial monitor. You can easily modify it to display in Celsius or adapt it for other display methods.

// Arduino code to read GM coolant sensor 12146312
// Outputs temperature in Fahrenheit via serial monitor

#include <math.h> // Include math library for Steinhart-Hart equation

void setup() {
  Serial.begin(115200); // Initialize serial communication at 115200 baud rate
}

double Thermister(int RawADC) { // Function to calculate temperature using Steinhart-Hart equation
  double Temp;
  Temp = log(((10240000/RawADC) - 10000)); // Steinhart-Hart equation - part 1
  Temp = 1 / (0.001129148 + (0.000234125 + (0.0000000876741 * Temp * Temp ))* Temp ); // Steinhart-Hart equation - part 2
  Temp = Temp - 273.15; // Convert Kelvin to Celsius
  Temp = (Temp * 9.0)/ 5.0 + 32.0; // Convert Celsius to Fahrenheit
  return Temp;
}

void loop() {
  int val; // Variable to store analog reading
  double temp; // Variable to hold temperature value
  val = analogRead(0); // Read analog value from pin A0
  temp = Thermister(val); // Convert analog value to temperature
  Serial.print ("Coolant Temperature: "); // Label for serial output
  Serial.println(temp); // Print temperature value to serial monitor
  delay(1000); // Wait for 1 second before next reading
}

Code Explanation:

• #include <math.h>: This line includes the math library, which is necessary for the log() function used in the Steinhart-Hart equation.
• Serial.begin(115200);: Initializes serial communication, allowing you to view the temperature readings in the Arduino Serial Monitor. The baud rate is set to 115200 for faster data transfer.
• double Thermister(int RawADC): This function implements the Steinhart-Hart equation, a mathematical model used to convert the resistance of a thermistor (like the coolant temperature sensor) into a temperature reading. The equation is broken into two parts for clarity. The raw analog reading from the Arduino’s ADC is passed into this function.
• Temp = log(((10240000/RawADC) - 10000)); and Temp = 1 / (0.001129148 + (0.000234125 + (0.0000000876741 * Temp * Temp ))* Temp );: These lines are the Steinhart-Hart equation itself. The constants (0.001129148, 0.000234125, 0.0000000876741) are specific to the GM 12146312 coolant temperature sensor and are derived from its datasheet.
• Temp = Temp - 273.15;: Converts the temperature from Kelvin to Celsius.
• Temp = (Temp * 9.0)/ 5.0 + 32.0;: Converts the temperature from Celsius to Fahrenheit. You can comment out this line and uncomment the previous line if you need the temperature in Celsius.
• void loop(): The main loop of the Arduino program.
• val = analogRead(0);: Reads the analog voltage value from Analog pin 0 and stores it in the val variable. This raw analog value represents the sensor’s resistance, which changes with temperature.
• temp = Thermister(val);: Calls the Thermister function to convert the raw analog reading (val) into a temperature value and stores it in the temp variable.
• Serial.print ("Coolant Temperature: "); and Serial.println(temp);: Prints the temperature reading to the Serial Monitor with a descriptive label.
• delay(1000);: Pauses the program for 1 second before taking the next reading.

This setup provides a basic yet functional way to read coolant temp sensor code using an Arduino and a GM 12146312 sensor. You can now monitor coolant temperature for various DIY automotive projects or experiments. Remember to always verify the sensor readings and ensure proper wiring for accurate results.