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Custom IoT Hardware Carriers

The core physical foundation of this IoT ecosystem is a pair of custom open-hardware PCB carrier boards designed in KiCad. These boards break out microcontrollers, precision environmental sensors, and low-power e-paper displays into compact modules that mount directly onto standard LEGO plates and enclosures.

Carrier Board Family

  • Sensor Board 12x6 Both Sides

    Sensor Carrier 12×6 (Rev 1, 2, 3)

    • Footprint: 12×6 LEGO plate (96 mm × 48 mm)
    • Microcontroller: ESP32-C3 SuperMini (Rev 3) / ESP32-C3-FH4 WeAct (Rev 1 & 2)
    • Display Options: WeAct 2.13" E-Paper (122 × 250) or 1.54" E-Paper (200 × 200)
    • Sensors: BME280 / BME680, SGP30 / SGP40, TEMT6000 light sensor
    • Socketing: Through-hole sockets for modular replacement of MCU and sensors

    Read 12×6 Carrier specifications

  • 1.54" E-Paper 3D View

    Mini Sensor Carrier 8×6

    • Footprint: 8×6 LEGO plate (64 mm × 48 mm)
    • Microcontroller: ESP32-C6 SuperMini (WiFi 6, BLE 5, Zigbee/Thread capability)
    • Display: Dedicated WeAct 1.54" E-Paper (200 × 200, SSD1680/SSD1681)
    • Sensors: BME680 via SPI bus (T/P/H/VOC), TEMT6000 ambient light sensor
    • Optimization: Ultra-compact surface-mount jumpers with direct LCSC manufacturing BOM

    Read 8×6 Mini Carrier specifications

Hardware Comparison Matrix

Feature 12×6 Sensor Carrier (Rev 3) 8×6 Mini Sensor Carrier
Target Repository m-lego/sensor m-lego/sensor-1.54
Grid Dimensions 12 studs × 6 studs (96 × 48 mm) 8 studs × 6 studs (64 × 48 mm)
Mounting Holes 4 corner holes + 2 center (4.8 mm dia) 4 corner holes (4.8 mm dia)
Microcontroller ESP32-C3 SuperMini ESP32-C6 SuperMini
Wireless Protocols 2.4 GHz Wi-Fi 4 (802.11b/g/n), BLE 5 Wi-Fi 6 (802.11ax), BLE 5.3, Zigbee, Thread
Supported Displays 2.13" B&W/BWR or 1.54" B&W WeAct 1.54" B&W/BWR WeAct E-Paper
Climate Sensor BME280 (I2C) or BME680 (SPI) BME680 (SPI bus)
Air Quality (VOC) SGP30 or SGP40 (I2C) BME680 integrated gas resistance
Light Sensor TEMT6000 (Analog ADC) TEMT6000 (Analog ADC)
Bussing Dedicated SPI bus + I2C bus Unified high-speed SPI bus
Power Supply 5V USB-C or 3.3V header rail 5V USB-C or 3.3V header rail

Supported Sensor Suite

graph LR
    subgraph MCU ["ESP32 Controller"]
        SPI["SPI Bus<br>(CLK, MOSI, MISO)"]
        I2C["I2C Bus<br>(SDA, SCL)"]
        ADC["ADC Input<br>(Analog GPIO)"]
    end

    subgraph Peripherals ["Sensors & Displays"]
        EPD["WeAct E-Paper Display<br>(CS, DC, RST, BUSY)"]
        BME680["Bosch BME680<br>(Temp, Humidity, Pressure, Gas)"]
        BME280["Bosch BME280<br>(Temp, Humidity, Barometer)"]
        SGP["Sensirion SGP40<br>(VOC Index Algorithm)"]
        TEMT["TEMT6000 Sensor<br>(Illuminance / Lux)"]
    end

    SPI --> EPD
    SPI --> BME680
    I2C --> BME280
    I2C --> SGP
    ADC --> TEMT

1. Environmental Sensing

  • Bosch BME280: Combined digital temperature, relative humidity, and barometric pressure sensor communicating over I2C (0x76 or 0x77). Extremely stable baselines and low current draw.
  • Bosch BME680: Upgraded 4-in-1 sensor with volatile organic compound (VOC) gas sensing and metal oxide resistance measurements, connected over high-speed hardware SPI.
  • Sensirion SGP30 / SGP40: Dedicated metal-oxide gas sensor calculating indoor VOC index (1–500 scale) with on-chip humidity compensation fed directly from the BME280 state.

2. Ambient Light & Power Gating

  • TEMT6000: High-sensitivity phototransistor tuned to human eye sensitivity (~570 nm peak). Output voltage directly correlates with room illuminance.
  • Used across the ESPHome fleet to conditionally inhibit E-Paper display refreshes whenever the ambient light level drops below 1.0 lx (e.g. night in bedrooms), avoiding unwanted ghosting clears or clicking relays.

Why Modular LEGO Enclosures?

  1. Precision & Consistency — Injection-molded LEGO bricks provide tolerances under 0.01 mm, eliminating warping, layering defects, and brittle clips typical of budget FDM 3D printing.
  2. Infinite Reconfiguration — Convert a tabletop desk clock into a wall-hanging display or angled dashboard bracket in seconds without re-designing CAD models.
  3. Thermal Management — Generous clearance and open grid construction prevent heat from the ESP32 power converter from skewing adjacent temperature readings.
  4. Learn more in the LEGO Mounting & CAD Guide.