G3MB-202P Solid State Relay — 5V Logic Input, 100–240VAC / 2A Output, Zero-Cross, Opto-Isolated

G3MB-202P Solid State Relay — 5V Logic, 100–240VAC / 2A, Zero-Cross Switching

The Omron G3MB-202P is a miniature single-channel solid state relay (SSR) that switches 100–240VAC at up to 2A from a 5V logic control signal. Unlike electromechanical relays, the G3MB-202P has no moving parts — it switches silently, instantly, and with no contact wear. Built-in phototriac coupler isolation provides electrical separation between the low-voltage control circuit and the mains AC load. Zero-cross switching minimizes electrical noise and inrush current by switching only at the AC waveform zero-crossing point.

The G3MB-202P is the SSR used in the majority of Chinese-made SSR relay modules. Available here as a standalone component for custom SSR circuit design, module repair, or direct integration into PCB designs.

Key Specifications

Control Input Voltage	4–6V DC (5V typical)
Logic HIGH threshold	≥4V
Logic LOW threshold	≤1.0V
Control Input Current	<14mA (directly drivable from MCU GPIO)
Output Voltage Range	75–264VAC (recommended: 100–240VAC)
Output Current	0.1–2A
Max Inrush Current	30A (8.3ms)
Switching Type	Zero-cross (switches at AC waveform zero point)
Isolation	Phototriac coupler (built-in opto-isolation)
Output Type	SPST Normally Open (NO)
Switching Speed	Every half-cycle (~8.3ms @ 60Hz)
Dimensions	24.5 × 20.5 × 5.5mm
Manufacturer	Omron

SSR vs Electromechanical Relay — Key Differences

	Electromechanical Relay	G3MB-202P SSR (this)
Moving parts	Yes (contacts wear over time)	No (unlimited switching life)
Switching noise	Audible click	Silent
Switching speed	~10ms	~8.3ms (zero-cross)
DC switching	Yes	No (AC only)
Parallel operation	Yes	No (do not parallel for higher current)
Max current	10A+ typical	2A

Wiring Guide

• Pin 3 (+) → MCU GPIO (logic HIGH = relay ON). Draws <14mA — safe for direct GPIO connection.
• Pin 4 (−) → GND (shared with MCU ground)
• Output terminals (1, 2) → In series with AC load and AC power source

Important: When switching mains AC voltage, ensure all connections are properly insulated and inaccessible. The G3MB-202P body is not insulated — mount on an insulating surface or use an SSR module with enclosure.

Important Limitations

• AC only — cannot switch DC voltages
• No parallel operation for higher current — SSRs do not share current equally; the first to turn on carries full load until it fails
• No dimming — zero-cross switching means ON/OFF only, not phase-angle dimming
• 2A maximum — for higher current AC switching, use a larger SSR or electromechanical relay

Typical Applications

• Arduino / ESP32 AC mains switching (lamps, fans, small appliances ≤2A)
• 3D printer heated bed control (12V DC bed — use electromechanical relay instead)
• Aquarium heater and pump control
• HVAC zone valve control
• Custom SSR module design and PCB integration
• SSR relay module repair and component replacement

Package Contents

• 1 × Omron G3MB-202P Solid State Relay

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