Documentation

Overview

This 4-channel solid state relay module switches four independent AC loads with no moving parts. Each channel is an Omron G3MB-202P solid state relay: an opto-triac device that couples your logic signal to the AC side through light, switching 24–240 V AC at up to 2 A per channel. No coil, no click, no contact wear — and switching happens at the AC zero-crossing, which keeps electrical noise remarkably low.

The module is high-level trigger: drive a channel input HIGH and that channel’s SSR conducts, with an LED confirming the state. Inputs arrive twice — a pin header and a duplicate screw-terminal block — and each channel’s AC path runs through its own replaceable 2 A fuse. Power the logic side with 4–6 V on DC+/DC− and the four channel pins connect directly to microcontroller GPIOs.

One boundary to respect before wiring anything: solid state relays of this type switch AC only — a triac never turns off on DC — and 2 A is a real ceiling, not a suggestion. Within those limits it is the clean, silent way to switch lamps, fans, pumps, and heaters. This manual covers the pinout, wiring for four platforms, code, and the SSR-specific questions that surprise people.

At a Glance

Specifications

Pinout Diagram

Left side: the control inputs — DC+ (4–6 V), DC− (ground), and CH1–CH4, available on both the header and the screw-terminal block. Right side: four 2-position AC output terminals, one per channel, each in series with its green 2 A fuse. The channel LEDs sit beside the input header.

Wiring Guide

Code Examples

Arduino — Four-Channel Sequencer

const int CH[4] = {4, 5, 6, 7};

void setup() {
  for (int i = 0; i < 4; i++) {
    pinMode(CH[i], OUTPUT);
    digitalWrite(CH[i], LOW);   // all off at boot
  }
}

void loop() {
  for (int i = 0; i < 4; i++) {
    digitalWrite(CH[i], HIGH);  // ON
    delay(1000);
    digitalWrite(CH[i], LOW);   // OFF
  }
}

ESP32 — Timed Channel Control

const int CH[4] = {25, 26, 27, 33};

void setup() {
  Serial.begin(115200);
  for (int i = 0; i < 4; i++) {
    pinMode(CH[i], OUTPUT);
    digitalWrite(CH[i], LOW);
  }
}

void loop() {
  // channel 1 on a 10 s cycle, channel 2 opposite phase
  bool phase = (millis() / 10000) % 2;
  digitalWrite(CH[0], phase);
  digitalWrite(CH[1], !phase);
  Serial.printf("CH1=%d CH2=%d\n", phase, !phase);
  delay(500);
}

Raspberry Pi — Python (gpiozero)

from gpiozero import DigitalOutputDevice
from time import sleep

# active_high=True: HIGH turns the channel on
channels = [DigitalOutputDevice(pin, active_high=True, initial_value=False)
            for pin in (17, 27, 22, 23)]

try:
    while True:
        for i, ch in enumerate(channels, start=1):
            ch.on()
            print(f"Channel {i} ON")
            sleep(1)
            ch.off()
except KeyboardInterrupt:
    for ch in channels:
        ch.off()

Raspberry Pi Pico — MicroPython

from machine import Pin
import time

channels = [Pin(n, Pin.OUT, value=0) for n in (2, 3, 4, 5)]

while True:
    # all on together, then off one by one
    for ch in channels:
        ch.value(1)
    time.sleep(2)
    for ch in channels:
        ch.value(0)
        time.sleep(0.5)

Frequently Asked Questions

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