@tutorial: Homemade Spot Welder with Microwave transformer

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#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

// OLED Display Configuration
#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

// Hardware Pin Definitions (Check scheamtic)
const int TRIAC_PIN = 9;     // Output to the MOC3052 optocoupler input
const int PEDAL_PIN = 8;     // Foot switch input (INPUT_PULLUP)
const int BTN_UP = 2;        // Menu Button Up / Safety Toggle
const int BTN_DOWN = 4;      // Menu Button Down
const int BUZZER_PIN = 5;    // Piezo buzzer pin for audio feedback
const int POT_PULSE_1 = A0;  // Potentiometer 1: Pre-weld pulse duration
const int POT_PULSE_2 = A1;  // Potentiometer 2: Main weld pulse duration

// Variables for Weld Timings
int pulse1_ms = 15;
int pulse2_ms = 60;
const unsigned long PAUSE_BETWEEN_PULSES = 40; // 40ms settling gap

// Safety and System States
bool systemArmed = false;    // System starts in SAFE mode
bool welding = false;
unsigned long lastButtonPress = 0;

void setup() {
  pinMode(TRIAC_PIN, OUTPUT);
  pinMode(PEDAL_PIN, INPUT_PULLUP);
  pinMode(BTN_UP, INPUT_PULLUP);
  pinMode(BTN_DOWN, INPUT_PULLUP);
  pinMode(BUZZER_PIN, OUTPUT);
  
  digitalWrite(TRIAC_PIN, LOW); // Force TRIAC off at boot

  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) { 
    for(;;); // Halt if screen fails
  }
  
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  
  // System start beep
  tone(BUZZER_PIN, 1800, 150);
}

void loop() {
  readPotentiometersWithFilter();
  handleButtons();
  checkPedal();
  updateDisplay();
}

// Software smoothing filter to prevent potentiometer value jumping/jittering
void readPotentiometersWithFilter() {
  int raw1 = analogRead(POT_PULSE_1);
  int targetPulse1 = map(raw1, 0, 1023, 0, 60); // 0ms (OFF) to 60ms
  
  // Only update value if knob moves by more than 1ms (filters out minor noise)
  if (abs(targetPulse1 - pulse1_ms) > 1 || targetPulse1 == 0) {
    pulse1_ms = targetPulse1;
  }

  int raw2 = analogRead(POT_PULSE_2);
  int targetPulse2 = map(raw2, 0, 1023, 15, 300); // 15ms to 300ms
  
  if (abs(targetPulse2 - pulse2_ms) > 2) {
    pulse2_ms = targetPulse2;
  }
}

void handleButtons() {
  // Use UP Button to toggle Armed/Safe mode for security
  if (digitalRead(BTN_UP) == LOW) {
    if (millis() - lastButtonPress > 300) {
      systemArmed = !systemArmed;
      if (systemArmed) {
        tone(BUZZER_PIN, 2800, 150); // High pitch double beep for ARMED
        delay(100);
        tone(BUZZER_PIN, 2800, 150);
      } else {
        tone(BUZZER_PIN, 1200, 300); // Low long pitch tone for SAFE
      }
      lastButtonPress = millis();
    }
  }
  
  // Down button reserved for future menu expansions (like a counter reset)
  if (digitalRead(BTN_DOWN) == LOW) {
    if (millis() - lastButtonPress > 300) {
      tone(BUZZER_PIN, 2000, 30); // Short click
      lastButtonPress = millis();
    }
  }
}

void checkPedal() {
  if (digitalRead(PEDAL_PIN) == LOW && !welding) {
    // Only fire if the system has been explicitly armed via the button
    if (systemArmed) {
      executeWeldSequence();
    } else {
      // Alert user they forgot to arm the system
      tone(BUZZER_PIN, 800, 200); 
      delay(300);
    }
  }
}

void executeWeldSequence() {
  welding = true;
  
  // Pre-weld count-down tone
  tone(BUZZER_PIN, 2500, 80); 
  delay(200); 

  // --- PULSE 1 (Fires only if potentiometer is turned past 0) ---
  if (pulse1_ms > 0) {
    digitalWrite(TRIAC_PIN, HIGH);   
    delay(pulse1_ms);            
    digitalWrite(TRIAC_PIN, LOW);    
    delay(PAUSE_BETWEEN_PULSES);     // Settlement window
  }

  // --- PULSE 2 (Main Weld) ---
  digitalWrite(TRIAC_PIN, HIGH);     
  delay(pulse2_ms);             
  digitalWrite(TRIAC_PIN, LOW);      

  // Fire confirmation tone
  tone(BUZZER_PIN, 1500, 100);
  
  // Safety Lockout: Hold program until pedal is fully released
  while(digitalRead(PEDAL_PIN) == LOW) {
    delay(10); 
  }
  
  delay(500); // Thermal cooling delay
  welding = false;
}

void updateDisplay() {
  display.clearDisplay();
  
  // Status Bar
  display.setCursor(0, 0);
  if (systemArmed) {
    display.print("STATUS: ** ARMED **");
  } else {
    display.print("STATUS:    LOCKED ");
  }
  
  display.drawFastHLine(0, 11, 128, SSD1306_WHITE);
  
  // Potentiometer 1 Readout
  display.setCursor(0, 22);
  display.print("P1 Pre-Weld: ");
  if (pulse1_ms == 0) {
    display.print("OFF");
  } else {
    display.print(pulse1_ms);
    display.print(" ms");
  }
  
  // Potentiometer 2 Readout
  display.setCursor(0, 42);
  display.print("P2 MainWeld: ");
  display.print(pulse2_ms);
  display.print(" ms");
  
  // Quick Menu Hint
  display.setCursor(0, 56);
  display.setTextSize(0); 
  display.print("Press UP to Lock/Arm");
  display.setTextSize(1);
  
  display.display();
}