🛠 Commander une charge 230 V avec un relais de sortie

Objectives

Control a power load via the Opta's 4 relay outputs. Each relay is a NO (SPST) contact rated 10 A / 250 VAC (up to 400 VAC), with a 6 ms operate time, 3 ms bounce time, and a mechanical life of 10 million cycles. The critical point: there is no internal protection against short circuits, so an external fuse is mandatory.

Hardware

• Arduino Opta powered by 24 VDC (USB-C cannot power the relays)
• A load: 230 V bulb, test resistor, or contactor coil
• Fuse holder + appropriately rated fuse in series with the load (mandatory)
• Suitable power wire, tester

Complete code

// opta_sortie_relais.ino — cycle de test sur OUTPUT1 (RELAY1, broche D0)

const int CHARGE = RELAY1; // OUTPUT1 : contact NO 10 A / 250 VAC

void setup {
  Serial.begin(9600);
  pinMode(CHARGE, OUTPUT);
  digitalWrite(CHARGE, LOW); // defaut securise : contact ouvert
}

void loop {
  digitalWrite(CHARGE, HIGH); // fermeture du contact
  Serial.println("CHARGE ON");
  delay(2000);
  digitalWrite(CHARGE, LOW);  // ouverture
  Serial.println("CHARGE OFF");
  delay(2000);
}

Expected verification

You will hear the relay click every 2 seconds, and the load will turn on/off. The serial monitor reports the state. The contact at rest (default) must be open: this is the safe mode.

Common errors

• No external fuse: The Opta has NO internal relay protection; a short circuit will destroy the contact. Size the fuse according to the load.
• Relay overload: 10 A max resistive, and only 10,000 cycles at this level; for a motor or inductive load (AC15 500 VA), use a contactor and limit the switching frequency.
• Forgetting the minimum load: Below 300 mW (5 V / 5 mA), the contact may become sulfated and fail to conduct current.
• Connecting 230 V to an input terminal: Check the terminal three times. OUTPUT1..4 = relays, I1..I8 = inputs only.