🛠 Lire une entrée numérique 24 V (capteur de proximité)

Objectives

Read a real industrial signal on the Opta's multifunction inputs. The 8 inputs I1..I8 (pins A0..A7) accept 0–24 VDC directly: no conditioning card is required. VIH threshold ≥ 6.6 V, VIL ≤ 4.46 V, impedance 8.9 kΩ, overvoltage and reverse polarity protection.

Hardware

• Arduino Opta with 24 VDC power supply on the power terminals (12–24 VDC, tightening torque 0.80 Nm)
• A 3-wire PNP inductive proximity sensor (or a simple button connected to +24 V)
• Wires 0.5–6 mm², insulated screwdriver
• Arduino IDE with the Opta core

Complete code

// opta_entree_24v.ino — etat d'un capteur sur I1 (broche A0)

const int CAPTEUR = A0; // borne I1 : 0 V / +24 V, VIH >= 6,6 V

void setup {
  Serial.begin(9600);
  pinMode(CAPTEUR, INPUT); // entree 24 V toleree, 8,9 kOhm
}

void loop {
  bool present = digitalRead(CAPTEUR) == HIGH;
  Serial.println(present ? "PIECE PRESENTE" : "RIEN");
  delay(50);
}

Expected verification

Bring a metal piece close to the sensor (or close the button towards +24 V): the serial monitor displays "PIECE PRESENTE". At rest, the input below 4.46 V reads LOW. The input is protected against reverse polarity, but respect the 0–24 VDC range.

Common errors

• PNP/NPN confusion: the Opta expects a source signal (+24 V on the terminal); an NPN sensor (sinking) will not drive the input correctly without adaptation.
• Forgetting sensor power: the 24 V on the input terminals is not a sensor power supply, provide a separate 24 V power supply for the sensors.
• Watch out for interrupts: terminals I1 (A0) and I4 (A3) cannot use interrupts simultaneously (documented limitation in the user manual).
• Floating input: an unwired input may oscillate; in production, connect a real load or a 0 V reference.