{"product_id":"iotextra-octal3-digital-io-latching-relay-module","title":"IoTextra Octal3 — Digital I\/O with Latching Relay Module","description":"\u003c!-- IoTextra Octal3 — Shopify Product Card --\u003e\n\u003cp\u003e\u003cbr\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cimg src=\"https:\/\/raw.githubusercontent.com\/makethingshappy\/IoTextra-Digital\/main\/Octal3\/overview.svg\"\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cimg src=\"https:\/\/raw.githubusercontent.com\/makethingshappy\/IoTextra-Digital\/main\/Octal3\/software.svg\"\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cimg src=\"https:\/\/raw.githubusercontent.com\/makethingshappy\/IoTextra-Digital\/main\/Octal3\/latching.svg\"\u003e\u003c\/p\u003e\n\u003cp\u003e\u003cb\u003e\u003cspan style=\"font-size: 14.0pt;\"\u003eKey Features\u003c\/span\u003e\u003c\/b\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cb\u003e4 Latching DPDT Relays (KEMET EC2-5SNU):\u003c\/b\u003e Bistable relays that retain their state without coil power — no heat, no holding current, no unexpected switching on power failure.\u003c\/li\u003e\n\u003cli\u003e\n\u003cb\u003eState Retention Across Power Cycles:\u003c\/b\u003e Relay contacts hold position mechanically. The relay is exactly where you left it when power returns.\u003c\/li\u003e\n\u003cli\u003e\n\u003cb\u003eIndustrial-Grade Isolation:\u003c\/b\u003e All digital channels feature individual galvanic isolation with a dielectric strength of \u003cb\u003e3750 Vrms\u003c\/b\u003e.\u003c\/li\u003e\n\u003cli\u003e\n\u003cb\u003eHigh-Voltage Input:\u003c\/b\u003e Digital input signals handle up to \u003cb\u003e36 VDC\u003c\/b\u003e.\u003c\/li\u003e\n\u003cli\u003e\n\u003cb\u003eRelay Switching Capacity:\u003c\/b\u003e 2A at \u003cb\u003e250 VAC \/ 220 VDC\u003c\/b\u003e.\u003c\/li\u003e\n\u003cli\u003e\n\u003cb\u003eH-Bridge Driver:\u003c\/b\u003e Relay switching performed via \u003cb\u003eTI DRV8837C\u003c\/b\u003e — polarity-reversal pulse generation, built-in flyback protection, no external diodes required.\u003c\/li\u003e\n\u003cli\u003e\n\u003cb\u003eI²C Control:\u003c\/b\u003e All relay outputs controlled via onboard \u003cb\u003eTCA9534A\u003c\/b\u003e I\/O expander. Address set by DIP switch (A0–A2). Up to 16 modules per I²C bus.\u003c\/li\u003e\n\u003cli\u003e\n\u003cb\u003enSLEEP Power Management:\u003c\/b\u003e Shared nSLEEP signal (AP5) enables\/disables all four DRV8837C drivers simultaneously — near-zero standby consumption.\u003c\/li\u003e\n\u003cli\u003e\n\u003cb\u003eLogic Thresholds (inputs):\u003c\/b\u003e 0–2 V (Logical \"1\"), 4–36 V (Logical \"0\").\u003c\/li\u003e\n\u003cli\u003e\n\u003cb\u003eStatus Indication:\u003c\/b\u003e Green LED per relay (LD_K1–K4) and LED per digital input channel.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cb\u003e\u003cspan style=\"font-size: 14.0pt;\"\u003eControl Architecture\u003c\/span\u003e\u003c\/b\u003e\u003c\/p\u003e\n\u003cp\u003eThe \u003cb\u003eIoTextra Octal3\u003c\/b\u003e requires both the \u003cb\u003eHOST\u003c\/b\u003e connector and the \u003cb\u003eI²C\u003c\/b\u003e bus. Digital inputs (IN1–IN4) are read directly via HOST signals AP0–AP3. Relay outputs are controlled via \u003cb\u003eI²C → TCA9534A → DRV8837C\u003c\/b\u003e. The nSLEEP line (AP5) must be driven High before any relay switching pulse and returned Low afterwards.\u003c\/p\u003e\n\u003cp\u003eUp to 16 modules can be connected to one I²C bus, provided that the \u003cb\u003enSLEEP\u003c\/b\u003e signal (shared across all modules or individual per module) is supplied to each module — this signal is required to enable the \u003cb\u003eDRV8837C\u003c\/b\u003e relay drivers.\u003c\/p\u003e\n\u003cp\u003e\u003cb\u003eImportant:\u003c\/b\u003e Relay state is not readable from hardware. The microcontroller must maintain relay state in EEPROM or flash and restore it on boot. The TCA9534A controls only the H-bridge inputs — no readback path from relay contacts exists.\u003c\/p\u003e\n\u003cp\u003e\u003cb\u003e\u003cspan style=\"font-size: 14.0pt;\"\u003eFlexible Operation Modes\u003c\/span\u003e\u003c\/b\u003e\u003c\/p\u003e\n\u003cp\u003eThe \u003cb\u003eIoTextra Octal3\u003c\/b\u003e features a \u003cb\u003eHOST-P\u003c\/b\u003e connector designed for three primary use cases:\u003c\/p\u003e\n\u003ctable style=\"width: 100%; border-collapse: separate; border-spacing: 10px;\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd style=\"width: 33%; vertical-align: top; background: #f7f9fc; border: 1px solid #e8edf5; border-radius: 8px; padding: 16px;\"\u003e\n\u003cp style=\"margin: 0 0 6px; font-size: 14px; font-weight: bold; color: #1a1a1a;\"\u003e🔌 Standalone\u003c\/p\u003e\n\u003cp style=\"margin: 0; font-size: 13px; color: #666666;\"\u003eConnect via HOST-P12 cable or \u003cb\u003eQwiic\u003c\/b\u003e I²C connectors from any host microcontroller (ESP32, RP2040, etc.).\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd style=\"width: 33%; vertical-align: top; background: #f7f9fc; border: 1px solid #e8edf5; border-radius: 8px; padding: 16px;\"\u003e\n\u003cp style=\"margin: 0 0 6px; font-size: 14px; font-weight: bold; color: #1a1a1a;\"\u003e🧠 Smart\u003c\/p\u003e\n\u003cp style=\"margin: 0; font-size: 13px; color: #666666;\"\u003eInsert an \u003cb\u003eIoTsmart\u003c\/b\u003e module (ESP32-S3, RP2350, RP2040, XIAO) vertically into HOST-P12 — one-board stack, no wiring.\u003c\/p\u003e\n\u003c\/td\u003e\n\u003ctd style=\"width: 33%; vertical-align: top; background: #f7f9fc; border: 1px solid #e8edf5; border-radius: 8px; padding: 16px;\"\u003e\n\u003cp style=\"margin: 0 0 6px; font-size: 14px; font-weight: bold; color: #1a1a1a;\"\u003e🏗 Mezzanine\u003c\/p\u003e\n\u003cp style=\"margin: 0; font-size: 13px; color: #666666;\"\u003eInstall into an \u003cb\u003eIoTbase\u003c\/b\u003e carrier board (PICO, Nano) for expanded system integration.\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003cp\u003e\u003cb\u003e\u003cspan style=\"font-size: 14.0pt;\"\u003eApplications\u003c\/span\u003e\u003c\/b\u003e\u003c\/p\u003e\n\u003ctable style=\"width: 100%; border-collapse: collapse;\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd style=\"width: 48px; vertical-align: top; padding: 12px 14px 12px 0;\"\u003e\n\u003cdiv style=\"width: 40px; height: 40px; background: #f0f4f8; border-radius: 8px; display: flex; align-items: center; justify-content: center; font-size: 20px; text-align: center; line-height: 40px;\"\u003e⚡\u003c\/div\u003e\n\u003c\/td\u003e\n\u003ctd style=\"vertical-align: top; padding: 12px 0; border-bottom: 1px solid #e8edf5;\"\u003e\n\u003cp style=\"margin: 0 0 3px; font-size: 14px; font-weight: bold; color: #1a1a1a;\"\u003eIIoT — Control Cabinet Management\u003c\/p\u003e\n\u003cp style=\"margin: 0; font-size: 13px; color: #666666;\"\u003eDigital inputs monitor circuit breakers and voltage presence; latching relays hold contactors or disconnect switches through power outages with zero coil energy consumption. Use with \u003cb\u003eNode-RED\u003c\/b\u003e or \u003cb\u003eIoTflow\u003c\/b\u003e for real-time cabinet monitoring.\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"width: 48px; vertical-align: top; padding: 12px 14px 12px 0;\"\u003e\n\u003cdiv style=\"width: 40px; height: 40px; background: #f0f4f8; border-radius: 8px; display: flex; align-items: center; justify-content: center; font-size: 20px; text-align: center; line-height: 40px;\"\u003e📡\u003c\/div\u003e\n\u003c\/td\u003e\n\u003ctd style=\"vertical-align: top; padding: 12px 0; border-bottom: 1px solid #e8edf5;\"\u003e\n\u003cp style=\"margin: 0 0 3px; font-size: 14px; font-weight: bold; color: #1a1a1a;\"\u003eTelecommunications — Bypass \u0026amp; Line Switching\u003c\/p\u003e\n\u003cp style=\"margin: 0; font-size: 13px; color: #666666;\"\u003ePhysical bypass switching of backup lines. Relays remain in position indefinitely without holding current — critical for equipment running continuously for years. Works with \u003cb\u003eTasmota\u003c\/b\u003e and \u003cb\u003eMQTT\u003c\/b\u003e.\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"width: 48px; vertical-align: top; padding: 12px 14px 12px 0;\"\u003e\n\u003cdiv style=\"width: 40px; height: 40px; background: #f0f4f8; border-radius: 8px; display: flex; align-items: center; justify-content: center; font-size: 20px; text-align: center; line-height: 40px;\"\u003e🌱\u003c\/div\u003e\n\u003c\/td\u003e\n\u003ctd style=\"vertical-align: top; padding: 12px 0; border-bottom: 1px solid #e8edf5;\"\u003e\n\u003cp style=\"margin: 0 0 3px; font-size: 14px; font-weight: bold; color: #1a1a1a;\"\u003eSmart Farming — Irrigation Control\u003c\/p\u003e\n\u003cp style=\"margin: 0; font-size: 13px; color: #666666;\"\u003eMonitor water level sensors and valve limit switches; activate irrigation valves with a short pulse and hold open with zero energy — ideal for solar-powered installations. Flexible scheduling with \u003cb\u003eNode-RED\u003c\/b\u003e and \u003cb\u003eIoTflow\u003c\/b\u003e.\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"width: 48px; vertical-align: top; padding: 12px 14px 12px 0;\"\u003e\n\u003cdiv style=\"width: 40px; height: 40px; background: #f0f4f8; border-radius: 8px; display: flex; align-items: center; justify-content: center; font-size: 20px; text-align: center; line-height: 40px;\"\u003e🏠\u003c\/div\u003e\n\u003c\/td\u003e\n\u003ctd style=\"vertical-align: top; padding: 12px 0;\"\u003e\n\u003cp style=\"margin: 0 0 3px; font-size: 14px; font-weight: bold; color: #1a1a1a;\"\u003eSmart Home — Blinds, Gates \u0026amp; Dampers\u003c\/p\u003e\n\u003cp style=\"margin: 0; font-size: 13px; color: #666666;\"\u003eConnect position sensors and manual buttons to inputs; relays retain last position after a power cut — no unexpected movement on power restoration. Integrates with \u003cb\u003eHome Assistant\u003c\/b\u003e.\u003c\/p\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003cp\u003e\u003cb\u003e\u003cspan style=\"font-size: 14.0pt;\"\u003eCompact Design\u003c\/span\u003e\u003c\/b\u003e\u003c\/p\u003e\n\u003cp\u003eThe module's compact size of \u003cb\u003e47×56 mm\u003c\/b\u003e and integrated mounting holes allow for easy installation in a base module or a Raspberry Pi.\u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e","brand":"Make Things Happy!","offers":[{"title":"HOST-12 and Qwiic (I2C)","offer_id":59709880336670,"sku":"040304302311","price":28.0,"currency_code":"USD","in_stock":true},{"title":"HOST-12","offer_id":59709880369438,"sku":"040304302309","price":27.0,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0860\/7481\/8846\/files\/01_-_IoTextra_Octal3_-_3D_view.png?v=1785418996","url":"https:\/\/makethingshappy.io\/products\/iotextra-octal3-digital-io-latching-relay-module","provider":"Make Things Happy!","version":"1.0","type":"link"}