HFD4/3-S Relay Module 3.3–5V for STM32 & 51 Microcontrollers

HFD4/3-S Thin Relay Module – 3.3V to 5V, STM32 & 51 MCU Compatible

Take precise control of your electronics projects with this compact HFD4/3-S Relay Module. Designed for compatibility with STM32, 51 series, and other popular microcontrollers, this slim relay module bridges the gap between low-voltage control signals and real-world switching tasks — perfect for hobbyists, engineers, and makers alike.

Made in Mainland China.

Key Features

• Wide Supply Voltage: Operates across a broad 3.3V–6V range, making it compatible with 3.3V (STM32, ESP32) and 5V (Arduino, 51 MCU) systems without extra circuitry.
• High-Level Trigger: Triggered by a high logic level (>1.3V), with low trigger current of just 1.8mA — easy on your microcontroller's GPIO pins.
• Low Standby Power: Quiescent current of only 5µA keeps your overall system power consumption minimal.
• Signal Switching Ready: Signal insertion loss <0.3dB @ 1KHz makes it ideal for clean signal routing and switching applications.
• Maximum Load Capacity: Handles up to 2A @ 30VDC and 0.5A @ 220VAC — suitable for both signal switching and small-load power control.
• Compact & Thin Form Factor: The slim HFD4/3-S design saves precious board space in tight enclosures or project boxes.
• Safety Note: For loads exceeding 60V, we strongly recommend using an insulation protection enclosure to prevent accidental contact.

Technical Specifications

Ideal Use Cases

• Microcontroller-driven automation and switching circuits
• Signal routing and on/off control in embedded systems
• Smart home DIY projects with STM32, ESP32, or Arduino
• Low-power IoT device control and prototyping

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Note: Please allow 2%–3% dimensional tolerance due to manual measurement. Product color may vary slightly from images due to monitor calibration differences.

Learn more: EPA guidance on lithium-ion battery handling

Frequently Asked Questions

Q: Is this relay module compatible with 3.3V microcontrollers like STM32 or ESP32?

A: Yes! The HFD4/3-S relay module supports a wide supply voltage range of 3.3V to 6V, making it fully compatible with 3.3V microcontrollers such as STM32 and ESP32, as well as 5V systems like Arduino and 51-series MCUs — no level shifter required.

Q: What is the maximum switching load this relay module can handle?

A: This relay module can switch up to 2A at 30VDC or 0.5A at 220VAC. For any load voltage exceeding 60V, it is strongly recommended to place the module inside an insulation protection enclosure to ensure safe operation.

Q: How much current does the GPIO pin need to provide to trigger the relay?

A: The relay requires a trigger current of just 1.8mA from the IO pin, and a high logic level greater than 1.3V (but below VCC). This is well within the output capability of virtually all modern microcontroller GPIO pins, so no additional driver transistor is needed in most cases.

Q: How many relay modules are included in one purchase?

A: Each order includes 1 piece of the HFD4/3-S relay module.

Production & Packaging Notice

To maintain high stock availability and fast shipping times, our items are sourced from multiple verified manufacturing facilities. While the core quality, materials, and product specifications remain identical, you may notice slight variations in the packaging design, manufacturing origin, or the wording of the printed instructions.