{"product_id":"hfd4-3-s-relay-module-3-3v-5v-stm32-microcontroller-industrial-control","title":"HFD4\/3-S Relay Module 3.3V–5V for STM32 Microcontrollers","description":"\n\u003ch2\u003eHFD4\/3-S Thin Relay Module — 3.3V to 5V, Low Power, Wide Compatibility\u003c\/h2\u003e\n\u003cp\u003eTake your electronics projects and industrial control systems to the next level with this compact \u003cstrong\u003eHFD4\/3-S Relay Module\u003c\/strong\u003e. Designed for seamless integration with STM32, 51, Arduino, Raspberry Pi, and other popular microcontrollers, this slim relay module delivers reliable signal switching and on\/off load control in a space-saving form factor. Whether you're building automation circuits, prototyping embedded systems, or designing industrial control boards, this module is engineered to perform.\u003c\/p\u003e\n\n\u003ch3\u003eKey Features\u003c\/h3\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eWide Supply Voltage:\u003c\/strong\u003e Operates across a broad 3.3V–6V range, making it compatible with 3.3V and 5V microcontroller systems without additional level shifters.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eLow Power Consumption:\u003c\/strong\u003e Quiescent current of just 5µA; action current of 40mA — ideal for battery-powered and energy-conscious designs.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eHigh-Level Trigger:\u003c\/strong\u003e Triggered by a logic-high signal greater than 1.3V (and below VCC), with a low level threshold below 0.5V. Trigger current: 1.8mA.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eGenerous Load Capacity:\u003c\/strong\u003e Supports up to 2A @ 30VDC and 0.5A @ 220VAC. \u003cem\u003eNote: For voltages exceeding 60V, an insulation protection enclosure is strongly recommended to prevent electric hazard.\u003c\/em\u003e\n\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eLow Signal Insertion Loss:\u003c\/strong\u003e Signal insertion loss \u0026lt;0.3dB @ 1kMHz — perfect for signal switching applications where integrity matters.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eCompact \u0026amp; Thin Design:\u003c\/strong\u003e The slim HFD4\/3-S relay fits tight PCB layouts and enclosures, saving valuable board space.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eTechnical Specifications\u003c\/h3\u003e\n\u003ctable style=\"width:100%; border-collapse:collapse;\"\u003e\n  \u003ctr style=\"background:#f5f5f5;\"\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003e\u003cstrong\u003eSupply Voltage (VCC)\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003e3.3V – 6V\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003e\u003cstrong\u003eQuiescent Current\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003e5µA\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr style=\"background:#f5f5f5;\"\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003e\u003cstrong\u003eAction Current\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003e40mA\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003e\u003cstrong\u003eTrigger Mode\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003eHigh Level (IO)\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr style=\"background:#f5f5f5;\"\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003e\u003cstrong\u003eTrigger Voltage (High)\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003e\u0026gt;1.3V, \u0026lt;VCC\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003e\u003cstrong\u003eTrigger Voltage (Low)\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003e\u0026lt;0.5V\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr style=\"background:#f5f5f5;\"\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003e\u003cstrong\u003eTrigger Current\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003e1.8mA\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003e\u003cstrong\u003eMax DC Load\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003e2A @ 30VDC\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr style=\"background:#f5f5f5;\"\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003e\u003cstrong\u003eMax AC Load\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003e0.5A @ 220VAC\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003e\u003cstrong\u003eSignal Insertion Loss\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003e\u0026lt;0.3dB @ 1kMHz\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr style=\"background:#f5f5f5;\"\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003e\u003cstrong\u003ePackage Quantity\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003e1 pc\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003e\u003cstrong\u003eCountry of Origin\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd style=\"padding:8px; border:1px solid #ddd;\"\u003eMade in China\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/table\u003e\n\n\u003ch3\u003eWho Is This For?\u003c\/h3\u003e\n\u003cp\u003eThis relay module is a go-to component for:\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eHobbyists and makers building DIY automation projects\u003c\/li\u003e\n  \u003cli\u003eEngineers prototyping embedded control systems\u003c\/li\u003e\n  \u003cli\u003eStudents learning microcontroller interfacing with STM32 or 51-series MCUs\u003c\/li\u003e\n  \u003cli\u003eIndustrial control applications requiring compact, reliable switching\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eExplore More Components for Your Projects\u003c\/h3\u003e\n\u003cp\u003eLooking for more parts to complete your builds? Check out these related items from our store:\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003e\u003ca href=\"\/products\/stainless-steel-cord-end-caps-with-loop-jewelry-making-6pcs\"\u003eStainless Steel Cord End Caps with Loop – 6pcs Jewelry Findings\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"\/products\/stainless-steel-flat-disc-spacer-beads-gold-silver-jewelry-making\"\u003eStainless Steel Flat Disc Spacer Beads Gold Silver – 20-50pcs\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"\/products\/metal-q-ring-spring-clasps-gold-silver-plated-jewelry-connectors\"\u003e10pcs Metal Q Ring Spring Clasps Gold Silver Plated Jewelry\u003c\/a\u003e\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003e\u003cem\u003ePlease allow a 2–3% dimensional variance due to manual measurement. Actual product color may differ slightly from images depending on your monitor settings.\u003c\/em\u003e\u003c\/p\u003e\n\n\u003cp\u003eLearn more: \u003ca href=\"https:\/\/www.osha.gov\/personal-protective-equipment\" target=\"_blank\" rel=\"noopener\"\u003eOSHA on personal protective equipment\u003c\/a\u003e\u003c\/p\u003e\n\u003ch3\u003eFrequently Asked Questions\u003c\/h3\u003e\n\u003ch4\u003eQ: Is the HFD4\/3-S relay module compatible with 3.3V microcontrollers like STM32?\u003c\/h4\u003e\n\u003cp\u003eA: 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, as well as 5V systems like Arduino and 51-series MCUs. No additional level-shifting circuitry is required for standard 3.3V logic outputs.\u003c\/p\u003e\n\u003ch4\u003eQ: What is the maximum load this relay module can switch?\u003c\/h4\u003e\n\u003cp\u003eA: The relay module can handle a maximum load of 2A at 30VDC or 0.5A at 220VAC. For safety, always use an insulation protection enclosure when working with voltages above 60V to prevent electrical hazard.\u003c\/p\u003e\n\u003ch4\u003eQ: How much power does this relay module consume when idle?\u003c\/h4\u003e\n\u003cp\u003eA: The module draws an extremely low quiescent (standby) current of just 5µA, making it well-suited for low-power and battery-operated designs. When activated, the action current is 40mA.\u003c\/p\u003e\n\u003ch4\u003eQ: What trigger signal does this relay module require?\u003c\/h4\u003e\n\u003cp\u003eA: The relay is triggered by a high-level logic signal. The trigger voltage must be greater than 1.3V (and below VCC) to activate, and below 0.5V to deactivate. The trigger current is only 1.8mA, so it is easily driven directly from standard microcontroller GPIO pins.\u003c\/p\u003e\n\u003c!-- production-packaging-notice --\u003e\n\u003ch3\u003eProduction \u0026amp; Packaging Notice\u003c\/h3\u003e\n\u003cp\u003eTo 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.\u003c\/p\u003e\n\u003cscript type=\"application\/ld+json\"\u003e{\"@context\": \"https:\/\/schema.org\", \"@type\": \"FAQPage\", \"mainEntity\": [{\"@type\": \"Question\", \"name\": \"Is the HFD4\/3-S relay module compatible with 3.3V microcontrollers like STM32?\", \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"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, as well as 5V systems like Arduino and 51-series MCUs. No additional level-shifting circuitry is required for standard 3.3V logic outputs.\"}}, {\"@type\": \"Question\", \"name\": \"What is the maximum load this relay module can switch?\", \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"The relay module can handle a maximum load of 2A at 30VDC or 0.5A at 220VAC. For safety, always use an insulation protection enclosure when working with voltages above 60V to prevent electrical hazard.\"}}, {\"@type\": \"Question\", \"name\": \"How much power does this relay module consume when idle?\", \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"The module draws an extremely low quiescent (standby) current of just 5µA, making it well-suited for low-power and battery-operated designs. 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