MICAMonitor for Indoor Climate & Air

CO₂VOCtemperaturehumiditypressure on a friendly 1.69″ screen, and in Home Assistant over Zigbee. Built on the ESP32-C6, powered over USB-C or an optional LiPo, in a 3D-printable case with open-source firmware under the Apache 2.0 license.

STL files Firmwarev0.1.1 Codev0.1.1

STL files

Files To Print Assembly Instructions

Software

The dashboard on a green border: temperature 18.7 °C, CO₂ 468 ppm, VOC 17 ppb, gas 180 kOhm, humidity 47.5 %, pressure 1013 hPa, each with an hour's sparkline — Fresh air

Printing

The dashboard on an orange border with a VOC warning tag, the VOC row highlighted at 3517 ppb — VOC alert

The dashboard on an orange border with a CO₂ warning tag, the CO₂ row highlighted at 1598 ppm — CO₂ alert

The dashboard with a VOC index of 150 and a NOx index of 3 — SGP41

The boot screen listing SCD41, SGP41, SGP30, SHT45 and BME680, each with a status dot — Boot

How to Flash

Install Rust, then espflash:
$cargo install espflash --locked
Download the firmware.
Plug the board in over USB-C and write it:
$espflash write-bin --chip esp32c6 0x0 air-monitor-0.1.1-esp32c6.bin

Build from source

Add the ESP32-C6 target and espflash:
$rustup target add riscv32imac-unknown-none-elf
$cargo install espflash --locked
Download the source code (Apache 2.0) and unzip it:
$unzip air-monitor-0.1.1-source.zip && cd air-monitor-0.1.1
Plug the board in, then build, flash and watch the log:
$make run

Buttons

Key	Click	Hold 2 s
BOOT	Wake	Fan test
PWR	Screen off	Power off

Home Assistant, over Zigbee

Sensors	Temperature, humidity, pressure, CO₂, VOC, battery
Fan	On, timed
Chime	Volume, repeat
Screen	Brightness, timeout
CO₂ calibration	Write the true CO₂

Assembly

Sensors

Cut one STEMMA QT cable and solder it to the board's header; chain the sensors in any order.

Red	`3V3`
Black	`G`
Blue	`SDA`
Yellow	`SCL`

Battery

It plugs into the board's BAT connector. Check the polarity first: many LiPo leads are wired the other way round for it.

Assembly Instructions

Components

Everything to buy for one monitor, besides the printed parts.

#	Part	Qty	Function	Source
Board and power
01	Waveshare ESP32-C6-LCD-1.69	1	MCU, 1.69″ screen, LiPo charger, buttons	Amazon
02	USB-C panel socket	1	Power and flashing through the body	Amazon
03	LiPo battery2000 mAh, 51.7 × 33.85 × 10.3 mm	1	Optional: runs it without USB
04	STEMMA QT cable	4	Sensor chain; one is cut for the board
SensorsAdafruit breakouts, chained over I²C
05	SCD41`0x62`	1	CO₂	Adafruit
06	SGP41 or SGP30`0x59 / 0x58`	1	VOC (SGP41: and NOx)	SGP41 SGP30
07	SHT45`0x44`	1	High Precision Temperature, Humidity	Adafruit
08	BME680`0x77`	1	Pressure, gas	Adafruit
Fan driverOptional, soldered
09	Fan30 × 30 × 10 mm, 5 V	1	Draws air past the sensors
10	BC337NPN transistor, TO-92	1	Switches the fan from the board's PWM
11	STPS5H100BSchottky diode, DPAK	1	Absorbs the fan's turn-off spike
12	Resistor330 Ω	1	Transistor base
13	Electrolytic capacitor220–470 µF	1	Fan supply, close to the fan
14	Ceramic capacitor100 nF–1 µF	1	Fan supply, close to the fan
Hardware
15	ScrewM2 × 6	19
16	ScrewM2 × 10	4
17	ScrewM2 × 16	4
18	ScrewM3 × 6	4
19	ScrewM3 × 8	4
20	ScrewM5 × 8	2
21	Heat-set insertM2 × 3, short	23
22	Heat-set insertM3 × 3, short	8
23	Heat-set insertM5 × 5.8, short	2
24	WasherM2, Ø5 / Ø2.2 × 0.5	13
25	MagnetØ6 × 3	16

Fan Driver

Solder it yourself: a transistor lets the board's PWM switch the 5 V fan; a diode absorbs its turn-off spike.