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12×6 LEGO Indoor Sensor Board (Rev 1, 2, 3)

The 12×6 Sensor Carrier (m-lego/sensor) is a full-featured modular environmental sensing platform designed to mount directly onto a standard 12×6 LEGO baseplate. It combines an ESP32 microcontroller with interchangeable e-paper displays, climate sensors, VOC air quality monitoring, and ambient light sensing.

Evolution & Revision History

  • Revision 1: Initial prototype utilizing the WeAct ESP32-C3-FH4 core module with a wide 24-way DIL socket and BME280 I2C sensor.
  • Revision 2: Added the TEMT6000 ambient light phototransistor circuit and support for SGP30/SGP40 air quality breakout headers.
  • Revision 3 (Current Production):
    • Standardized on the compact ESP32-C3 SuperMini footprint.
    • Added dedicated hardware SPI header routing for BME680 (allowing gas/VOC measurement alongside SPI displays).
    • Dual display mounting footprints: supports both 2.13" e-ink (122 × 250) and 1.54" e-ink (200 × 200) WeAct displays.
    • Integrated solder jumpers for voltage rail selection (3.3V vs 5V) and SPI chip select routing.

Schematic (Revision 3)

Schematic Rev 3 Click image to zoom full schematic in lightbox.

The schematic breaks out: 1. Microcontroller Bus: ESP32-C3 SuperMini 3.3V power, GND, hardware SPI (SCK GPIO4, MOSI GPIO6, MISO GPIO5), and hardware I2C (SDA GPIO8, SCL GPIO9). 2. Display Interface: 8-pin connector for WeAct E-Paper modules (BUSY: GPIO3, RST: GPIO2, DC: GPIO1, CS: GPIO7, SCK: GPIO4, MOSI: GPIO6). 3. Sensor Headers: * BME280 / BME680 dual footprint. * SGP30 / SGP40 header with pull-up resistors. * TEMT6000 analog light sensor fed into ADC channel (GPIO0).

PCB Layout & Silkscreen

PCB Rev 3 Both

PCB Rev 3 Front

PCB Rev 3 Back

- Front bare PCB Front Copper & Soldermask - Back bare PCB Back Copper & Soldermask

3D Renders with Mounted Displays

- 3D Front 2.13 inch Front View: 2.13" E-Paper & Sensors - 3D Back 2.13 inch Back View: ESP32-C3 SuperMini & Wiring

- 3D Front 1.54 inch Front View: 1.54" E-Paper & Sensors - 3D Back 1.54 inch Back View: ESP32-C3 SuperMini & Wiring

- PCB 3D Front Bare Front 3D Structure - PCB 3D Back Bare Back 3D Structure

Bill of Materials (BOM)

Component Designator / Model Description & Sourcing
Microcontroller ESP32-C3 SuperMini (Rev 3) 32-bit RISC-V @ 160MHz, 2.4GHz Wi-Fi, BLE 5, USB-C. Pinout compatible with LCSC C5364646. (Rev 1 & 2 use WeAct ESP32-C3-FH4).
E-Paper Display WeAct 2.13" or 1.54" 2.13" SSD1680 (122×250) or 1.54" SSD1681 (200×200) monochrome or 3-color panel.
Climate Sensor Bosch BME280 / BME680 BME280 (I2C) for Temp/Hum/Press, or BME680 (SPI Rev 3) for Temp/Hum/Press + VOC gas resistance.
Air Quality Sensirion SGP30 / SGP40 I2C breakout module for VOC index calculation.
Light Sensor TEMT6000 NPN phototransistor module with load resistor for analog illuminance.
Pull-Up Resistors R1, R2 (4.7 kΩ) I2C bus pull-ups for SDA and SCL rails.
DIL Socket 24-way wide socket Used on Rev 1 and 2 boards for modular chip insertion.
Mounting Base LEGO Plate 12×6 Standard 12×6 LEGO plate (e.g. LEGO Element ID 4875 / 3028).
Hardware M2.5 / M2 nylon standoffs 9 mm or 11 mm hexagonal standoffs for display standoff clearance.

Jumper Configurations

[!IMPORTANT] Verify voltage jumper settings before connecting sensors!

  • BME280 Jumper: If using a 5V-tolerant breakout board with on-board LDO, bridge the 5V jumper pad. If using a bare 3.3V module, bridge the 3.3V pad directly to avoid damaging the sensor.
  • BME680 SPI Chip Select: When using the BME680 over SPI, configure its dedicated CS pin in ESPHome without conflicting with the e-paper display CS pin (GPIO7).