IoTextra Octal3 — 4-channel isolated digital input and 4-channel latching DPDT relay module. Supply voltage: 5VDC, relay contacts up to 250VAC / 220VDC / 2A. Digital inputs up to 36VDC. Control via GPIO (inputs) and I²C / TCA9534A / DRV8837C (relay outputs). Compatible with ESP32-S3, RP2350, RP2040, Raspberry Pi, and IoTsmart. Supports Node-RED, IoTflow, Tasmota, and Home Assistant. Open Source Hardware.

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IoTextra Octal3 — Digital I/O with Latching Relay Module

Regular price: $28.00
Regular price
Sale price: $28.00

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SKU: 040304302311
Type: Digital IO
Availability: In Stock

DESCRIPTION

Key Features

4 Latching DPDT Relays (KEMET EC2-5SNU): Bistable relays that retain their state without coil power — no heat, no holding current, no unexpected switching on power failure.
State Retention Across Power Cycles: Relay contacts hold position mechanically. The relay is exactly where you left it when power returns.
Industrial-Grade Isolation: All digital channels feature individual galvanic isolation with a dielectric strength of 3750 Vrms.
High-Voltage Input: Digital input signals handle up to 36 VDC.
Relay Switching Capacity: 2A at 250 VAC / 220 VDC.
H-Bridge Driver: Relay switching performed via TI DRV8837C — polarity-reversal pulse generation, built-in flyback protection, no external diodes required.
I²C Control: All relay outputs controlled via onboard TCA9534A I/O expander. Address set by DIP switch (A0–A2). Up to 16 modules per I²C bus.
nSLEEP Power Management: Shared nSLEEP signal (AP5) enables/disables all four DRV8837C drivers simultaneously — near-zero standby consumption.
Logic Thresholds (inputs): 0–2 V (Logical "1"), 4–36 V (Logical "0").
Status Indication: Green LED per relay (LD_K1–K4) and LED per digital input channel.

Control Architecture

The IoTextra Octal3 requires both the HOST connector and the I²C bus. Digital inputs (IN1–IN4) are read directly via HOST signals AP0–AP3. Relay outputs are controlled via I²C → TCA9534A → DRV8837C. The nSLEEP line (AP5) must be driven High before any relay switching pulse and returned Low afterwards.

Up to 16 modules can be connected to one I²C bus, provided that the nSLEEP signal (shared across all modules or individual per module) is supplied to each module — this signal is required to enable the DRV8837C relay drivers.

Important: 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.

Flexible Operation Modes

The IoTextra Octal3 features a HOST-P connector designed for three primary use cases:

🔌 Standalone

Connect via HOST-P12 cable or Qwiic I²C connectors from any host microcontroller (ESP32, RP2040, etc.).

🧠 Smart

Insert an IoTsmart module (ESP32-S3, RP2350, RP2040, XIAO) vertically into HOST-P12 — one-board stack, no wiring.

🏗 Mezzanine

Install into an IoTbase carrier board (PICO, Nano) for expanded system integration.

Applications

⚡	IIoT — Control Cabinet Management Digital inputs monitor circuit breakers and voltage presence; latching relays hold contactors or disconnect switches through power outages with zero coil energy consumption. Use with Node-RED or IoTflow for real-time cabinet monitoring.
📡	Telecommunications — Bypass & Line Switching Physical bypass switching of backup lines. Relays remain in position indefinitely without holding current — critical for equipment running continuously for years. Works with Tasmota and MQTT.
🌱	Smart Farming — Irrigation Control Monitor 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 Node-RED and IoTflow.
🏠	Smart Home — Blinds, Gates & Dampers Connect position sensors and manual buttons to inputs; relays retain last position after a power cut — no unexpected movement on power restoration. Integrates with Home Assistant.