Circuit Documentation

Summary

This circuit is designed to function as a tachometer using an Arduino Nano as the central processing unit. It reads the rotational speed of an object via a Hall sensor and displays the measured RPM (Revolutions Per Minute) on an MKE-M07 LCD1602 I2C display. The circuit is powered by a 9V battery, and a diode is used to protect the Arduino from potential reverse voltage damage. The Hall sensor's output is connected to one of the digital pins of the Arduino, which counts the number of pulses per second to calculate the RPM. The LCD display communicates with the Arduino via the I2C protocol.

Component List

Arduino Nano

• Microcontroller board based on the ATmega328P
• Provides digital and analog I/O pins
• Features serial communication capabilities

MKE-M07 LCD1602 I2C

• Alphanumeric LCD display module with 16 characters and 2 lines
• Equipped with an I2C interface for communication

9V Battery

• Standard 9V battery used to power the circuit

Hall Sensor

• Magnetic field sensor that outputs a digital signal in response to a magnetic field
• Used to detect the presence of a magnet and thus the rotation of an object

Diode

• Semiconductor device that allows current to flow in one direction only
• Used to prevent reverse current flow that could damage the circuit

Wiring Details

Arduino Nano

• 5V pin connected to the 5V power rail
• GND pin connected to the ground rail
• VIN pin connected to the anode of the diode
• A4 pin connected to the SDA pin of the LCD display
• A5 pin connected to the SCL pin of the LCD display
• D5 pin connected to the S pin of the Hall sensor

MKE-M07 LCD1602 I2C

• GND pin connected to the ground rail
• 5V pin connected to the 5V power rail
• SDA pin connected to the A4 pin of the Arduino Nano
• SCL pin connected to the A5 pin of the Arduino Nano

9V Battery

• + pin connected to the cathode of the diode
• - pin connected to the ground rail

Hall Sensor

• + pin connected to the 5V power rail
• - pin connected to the ground rail
• S pin connected to the D5 pin of the Arduino Nano

Diode

• anode connected to the + pin of the 9V battery
• cathode connected to the VIN pin of the Arduino Nano

Documented Code

/*
 * Arduino Tachometer Project
 * This code reads the speed from a Hall sensor and displays it on an LCD.
 * Connections:
 * - Hall Sensor S pin to Arduino D5
 * - LCD SDA to Arduino A4
 * - LCD SCL to Arduino A5
 * - Power and ground connections as per the net list
 */

#include <Wire.h>
#include <LiquidCrystal_I2C.h>

// Initialize the LCD, address 0x27, 16 chars, 2 lines
LiquidCrystal_I2C lcd(0x27, 16, 2);

const int hallSensorPin = 5; // Hall sensor connected to D5
volatile int rpmCount = 0;
unsigned long lastTime = 0;

void setup() {
  pinMode(hallSensorPin, INPUT);
  attachInterrupt(digitalPinToInterrupt(hallSensorPin), rpmCounter, RISING);
  lcd.begin();
  lcd.backlight();
  lcd.setCursor(0, 0);
  lcd.print("Tachometer");
}

void loop() {
  unsigned long currentTime = millis();
  if (currentTime - lastTime >= 1000) { // Update every second
    detachInterrupt(digitalPinToInterrupt(hallSensorPin));
    int rpm = (rpmCount * 60); // Calculate RPM
    rpmCount = 0;
    lastTime = currentTime;
    lcd.setCursor(0, 1);
    lcd.print("RPM: ");
    lcd.print(rpm);
    attachInterrupt(digitalPinToInterrupt(hallSensorPin), rpmCounter, RISING);
  }
}

void rpmCounter() {
  rpmCount++;
}

This code is responsible for reading the number of pulses from the Hall sensor, which is indicative of the rotational speed. It then calculates the RPM and displays the value on the LCD. The rpmCounter function is an interrupt service routine that increments the rpmCount variable each time a pulse is detected from the Hall sensor. The main loop updates the display every second with the latest RPM value.