4-Channel Relay
Module Setup Guide

// 4-Channel Relay Module — Cycle Test
// Tishvi Docs · Wiring: VCC→5V | GND→GND | IN1..IN4→D2..D5
// Turns on relay K1, then K2, then K3, then K4, one at a time.

const int relayPins[4] = {2, 3, 4, 5}; // IN1..IN4

// Most boards in this family are LOW-level triggered.
// If your relays behave backwards, change this to false.
const bool RELAY_ACTIVE_LOW = true;

void relayWrite(int pin, bool on) {
  bool level = RELAY_ACTIVE_LOW ? !on : on;
  digitalWrite(pin, level ? HIGH : LOW);
}

void setup() {
  Serial.begin(9600);
  for (int i = 0; i < 4; i++) {
    pinMode(relayPins[i], OUTPUT);
    relayWrite(relayPins[i], false); // start OFF, before anything else
  }
  Serial.println("Cycling K1 -> K2 -> K3 -> K4...");
}

void loop() {
  for (int i = 0; i < 4; i++) {
    Serial.print("K");
    Serial.print(i + 1);
    Serial.println(" ON");
    relayWrite(relayPins[i], true);
    delay(1000);
    relayWrite(relayPins[i], false);
    delay(300);
  }
}

// 4-Channel Relay Module — Serial Command Control
// Type 1, 2, 3, or 4 in Serial Monitor to toggle that relay.
// Wiring: VCC→5V | GND→GND | IN1..IN4→D2..D5

const int relayPins[4] = {2, 3, 4, 5};
bool relayState[4] = {false, false, false, false};
const bool RELAY_ACTIVE_LOW = true; // flip if your board triggers HIGH

void relayWrite(int pin, bool on) {
  bool level = RELAY_ACTIVE_LOW ? !on : on;
  digitalWrite(pin, level ? HIGH : LOW);
}

void setup() {
  Serial.begin(9600);
  for (int i = 0; i < 4; i++) {
    pinMode(relayPins[i], OUTPUT);
    relayWrite(relayPins[i], false);
  }
  Serial.println("Send 1, 2, 3, or 4 to toggle that relay.");
}

void loop() {
  if (Serial.available()) {
    char c = Serial.read();
    if (c >= '1' && c <= '4') {
      int idx = c - '1';
      relayState[idx] = !relayState[idx];
      relayWrite(relayPins[idx], relayState[idx]);

      Serial.print("K");
      Serial.print(idx + 1);
      Serial.println(relayState[idx] ? " -> ON" : " -> OFF");
    }
  }
}