This code is an Arduino sketch that controls and logs...

September 2, 2025 at 09:29 PM

#include <SPI.h>
#include <SD.h>
#include <Wire.h>
#include <RTClib.h>

#define TV_RELAY 8
#define GEYSER_RELAY 9
#define SD_CS 3
#define PIR_PIN 7

#define TV_SENSOR A1
#define GEYSER_SENSOR A0

RTC_DS1307 rtc;
File logFile;

// Motion tracking
unsigned long lastMotionTime = 0;
const unsigned long MAX_INACTIVE_TIME = 2UL * 60UL * 60UL * 1000UL; // 2 hours in ms

void setup() {
  Serial.begin(9600);

  // Relays
  pinMode(TV_RELAY, OUTPUT);
  pinMode(GEYSER_RELAY, OUTPUT);
  digitalWrite(TV_RELAY, HIGH);     // Assume relay is active LOW
  digitalWrite(GEYSER_RELAY, HIGH);

  // PIR
  pinMode(PIR_PIN, INPUT);

  // RTC
  if (!rtc.begin()) {
    Serial.println("RTC not found!");
    while (1);
  }

  // SD
  if (!SD.begin(SD_CS)) {
    Serial.println("SD init failed!");
    while (1);
  }

  logFile = SD.open("energy.csv", FILE_WRITE);
  if (logFile) {
    logFile.println("Time,TV_Current,Geyser_Current,TV_Status,Geyser_Status");
    logFile.close();
  }
}

void loop() {
  // ==== Motion Detection ====
  if (digitalRead(PIR_PIN) == HIGH) {
    lastMotionTime = millis(); // Update motion timestamp
  }

  // Check inactivity for TV
  if (millis() - lastMotionTime > MAX_INACTIVE_TIME) {
    digitalWrite(TV_RELAY, HIGH); // TV off
  }

  // ==== Read Sensors ====
  float tvCurrent = analogRead(TV_SENSOR);     // raw for now
  float geyserCurrent = analogRead(GEYSER_SENSOR);

  // ==== Get Time ====
  DateTime now = rtc.now();

  // ==== Log Data ====
  logFile = SD.open("energy.csv", FILE_WRITE);
  if (logFile) {
    logFile.print(now.timestamp());
    logFile.print(",");
    logFile.print(tvCurrent);
    logFile.print(",");
    logFile.print(geyserCurrent);
    logFile.print(",");
    logFile.print(digitalRead(TV_RELAY) == LOW ? "ON" : "OFF");
    logFile.print(",");
    logFile.println(digitalRead(GEYSER_RELAY) == LOW ? "ON" : "OFF");
    logFile.close();
  }

  delay(5000); // log every 5s
}

This code is an Arduino sketch that controls and logs the energy usage of two devices (a TV and a geyser) while monitoring motion and inactivity using a PIR sensor. Here's a detailed breakdown of what it does:

Summary:

The code monitors motion using a PIR sensor, turns a TV off after 2 hours of inactivity, logs the current (sensor readings) and relay states (ON/OFF status) of the TV and geyser to an SD card, and timestamps the logs using an RTC (Real-Time Clock).

Key Components and Features:

Hardware Setup:
- Relay control for two devices:
  - TV_RELAY (Pin 8) controls the TV.
  - GEYSER_RELAY (Pin 9) controls the geyser.
  - The relays are assumed to be active LOW (they are ON when the pin is LOW and OFF when the pin is HIGH).
- Current sensors:
  - TV_SENSOR (Analog pin A1) measures the current (or some value) for the TV.
  - GEYSER_SENSOR (Analog pin A0) measures the current (or some value) for the geyser.
- PIR motion detection:
  - PIR_PIN (Digital pin 7) detects motion. When motion is detected, the PIR sensor's output is HIGH.
- SD card for logging:
  - Connected via SPI (SD_CS pin 3) to log data into a CSV file named energy.csv.
- RTC (Real-Time Clock):
  - The RTC (DS1307) provides the current date and time for timestamping the log entries.

Code Execution Flow:

setup():
- Sets up serial communication, pin modes for relays, and initializes the RTC, SD card, and log file:
  - Writes the CSV header (Time,TV_Current,Geyser_Current,TV_Status,Geyser_Status) to energy.csv on the SD card.
- Ensures proper functioning of the RTC and SD card or halts the program.
loop():
- Motion Detection & Inactivity Handling:
  - Monitors the PIR sensor for motion (PIR_PIN). If motion is detected, it updates lastMotionTime with the current time.
  - If no motion is detected for more than 2 hours (MAX_INACTIVE_TIME), the TV is turned off by setting TV_RELAY to HIGH.
- Sensor Readings:
  - Reads raw analog sensor values for TV_SENSOR and GEYSER_SENSOR to estimate current usage for the TV and geyser.
- Logging Data:
  - Retrieves the current timestamp from the RTC (rtc.now()).
  - Logs the following information into energy.csv:
    - Current timestamp (time).
    - Current readings (TV_SENSOR and GEYSER_SENSOR).
    - TV relay state (ON or OFF).
    - Geyser relay state (ON or OFF).
- Logs data every 5 seconds (delay(5000)).

Key Functionalities:
- Power Management:
  - Automatically turns off the TV after 2 hours of inactivity, conserving energy.
- Data Logging:
  - Records the energy usage (via current sensor readings) and the ON/OFF status of devices into a file on an SD card, providing a history for monitoring.
- Timestamping:
  - Uses a real-time clock (RTC) to timestamp the logged data for accurate records.
- Motion Tracking:
  - Tracks motion using a PIR sensor to determine when the TV should remain ON or turn OFF due to inactivity.

Example Log Entry:

A log entry might look like this (assuming placeholders for sensor data):

2023-10-12T10:45:30,345,123,ON,OFF

This means:

Timestamp: 2023-10-12T10:45:30.
TV current: 345 (raw sensor reading).
Geyser current: 123 (raw sensor reading).
TV status: ON (relay is LOW).
Geyser status: OFF (relay is HIGH).

Purpose:

This code automates controlling and monitoring energy usage and logs the relevant data for analysis. It is useful for building energy-efficient systems where monitoring and optimization of device usage is important.

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Built by @thebuilderjr