Floating SIgnal Fingerprint to Arduino

Projects General Guidance
1

please give me some solutions my project.

so this is interlock door acces control using arduino uno. using relay module LOW trigger, Reed Switch doorsensor, Fingerprint standalone, diode 1n40007.

PCB_pcb_interlock_2025-06-16 (1)
PCB_pcb_interlock_2025-06-16 (1)560×358 16.5 KB

so this the pcb wiring of my project. the problem is why if i testing with 1 diode connected with FP each the door, validation from FP still okei. but if i testing with 2 diode 2 FP to one line pin arduino, serial monitor read finger validation validation where I haven't done finger. and if i use diode mode multimeter to diode that connected NC FP, EMLOCK switching without FP. give me some suggestion

Screenshot 2025-06-30 112256
Screenshot 2025-06-30 112256616×377 45.2 KB

this my schematic

const int reedPin1 = 8;      // Sensor pintu 1 (NC) 
const int reedPin2 = 9;      // Sensor pintu 2 (NC)

const int fingerPin1 = 4;    // Fingerprint 1 (NC COM via diode+MOSFET)
const int fingerPin2 = 5;    // Fingerprint 2

const int relayPin1 = 2;    // Relay pintu 1
const int relayPin2 = 3;     // Relay pintu 2

unsigned long door1OpenTime = 0;
unsigned long door2OpenTime = 0;
const unsigned long relayOpenDuration = 3000; // Durasi relay ON (ms)

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

  pinMode(reedPin1, INPUT_PULLUP);
  pinMode(reedPin2, INPUT_PULLUP);

  pinMode(fingerPin1, INPUT_PULLUP);
  pinMode(fingerPin2, INPUT_PULLUP);

  pinMode(relayPin1, OUTPUT);
  pinMode(relayPin2, OUTPUT);

  digitalWrite(relayPin1, LOW);
  digitalWrite(relayPin2, LOW);
}

void loop() {
  unsigned long currentMillis = millis();

  // Handle pintu 1 dan pintu 2
  handleDoor(reedPin1, fingerPin1, relayPin1, reedPin2, door1OpenTime);
  handleDoor(reedPin2, fingerPin2, relayPin2, reedPin1, door2OpenTime);

  // Interlock safety: jika dua pintu terbuka bersamaan → matikan relay
  bool door1Open = digitalRead(reedPin1) == HIGH;
  bool door2Open = digitalRead(reedPin2) == HIGH;

  if (door1Open && door2Open) {
    Serial.println("❌ INTERLOCK VIOLATION: Kedua pintu terbuka!");
    digitalWrite(relayPin1, LOW);
    digitalWrite(relayPin2, LOW);
  }
}

// ======== FUNCTION UNTUK HANDLE TIAP PINTU ========
void handleDoor(int doorSensorPin, int fingerPin, int relayPin, 
                int otherDoorSensorPin, unsigned long &lastOpenTime) {
  unsigned long currentMillis = millis();

  bool doorOpen = digitalRead(doorSensorPin) == HIGH;
  bool otherDoorOpen = digitalRead(otherDoorSensorPin) == HIGH;
  bool fingerValid = digitalRead(fingerPin) == HIGH; // HIGH = fingerprint valid

  // Jika fingerprint valid dan pintu lain TERTUTUP, buka relay
  if (fingerValid && !otherDoorOpen) {
    Serial.print("✅ Finger valid di pin ");
    Serial.print(fingerPin);
    Serial.println(" → Buka pintu");

    digitalWrite(relayPin, HIGH);
    lastOpenTime = currentMillis;
  }

  // Matikan relay setelah durasi
  if (currentMillis - lastOpenTime > relayOpenDuration) {
    digitalWrite(relayPin, LOW);
  }
}


here my interlock code
2

Please edit your post, select all code and click the <CODE> button; next save your post.

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A schematic might also be useful.

3

thankyou for the suggestion, i just edited done

4

These four inputs are floating, without an obvious ground connection.
They will give spurious readings unless there is a ground reference.

Capture
Capture239×219 11.6 KB

What is the purpose of the diodes?