MH-Z19B

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Project MH-Z19B
Mhz19.jpg
Some research into the MH-Z19B CO2 sensor
Status Initializing
Contact Disasm
Last Update 2019-10-01

Introduction

MH-Z19B is an updated version of the MH-Z19 sensor.

Hardware

  • STM32F051K86 MCU
  • Unknown analog light+temperature sensor
  • Two 3.3V regulators
  • 1.5V voltage reference
  • Lamp

Teardown

Back side of the MH-Z19B sensor with unlabeled SWD pads on the right:

MH-Z19B-back.jpg

Front side of the (4-layer) PCB:

MH-Z19B-pcb.jpg MH-Z19B-pcb-markings.jpg MH-Z19B-pcb-tracks.jpg

Partial schematics:

MH-Z19B-schematics.png

Firmware

MCU firmware can be easily dumped through SWD pads. Pinout:

Pin Signal
1 (square) 3V3
2 GND
3 SWDIO
4 SWCLK
5 RESET (active low)

Additionally, bootloader asks for a firmware update during the first 20s of startup.