DustSensor

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Project Dust Sensor
Pms7003.jpg
Experiments with a dust sensor
Status Initializing
Contact bertrik
Last Update 2017-12-12

Introduction

I ordered a dust sensor module to perform measurements of airborne dust. In particular, I ordered this one, the Plantower PMS 7003, AliExpress link. It's being advertised as an advanced generation of dust sensor (7th generation), while still reasonably priced (E15,-). It uses lasers to perform the measurement and I think it contains a small fan to move the air around.

Hardware

Data sheets can be found:

The module takes 5V to run and communicates using 3.3V levels.

It makes an estimate of the number of particles per size category, total 6 categories: 0.3-0.5-1.0-2.5-5.0-10 micrometer. It also gives an estimate of the total mass of the particles in 3 categories: PM1.0, PM2.5 and PM10.

I plan to connect this thing up using an ESP8266.

Software

The software archive can be found at github, code has been written but not tested on actual hardware yet. Typing 'make' builds and runs unit tests that verify parsing of measurement data and construction of command data. The sub-directory 'pms7003_esp' contains the .ino file to be opened in the Arduino IDE.

Libraries used:

  • SoftwareSerial
  • WiFiClient
  • WiFiManager
  • PubSubClient

This dust sensor outputs its data as a 32-byte serial data stream at 9600 bps.

I plan to run the sensor in 'passive' mode. This means it's not doing a measurement unless the software explicitly tells it do one measurement.

Protocol outgoing data

The protocol for measurement data from the module is that data is sent in frames. Each frame starts with specific begin marker bytes, then a length byte, then the actual data, and finally a checksum. I think it is a good match to use a simple finite state machine to parse the stream and get synchronized to the frames.

Protocol
Value Meaning Remark
0x42 0x4D Begin marker ASCII for characters 'B' and 'M'
0x00 0x1C Length Length of following data
XX YY PM1.0 concentration (ug/m3) CF=1, standard particles
XX YY PM2.5 concentration (ug/m3) CF=1, standard particles
XX YY PM10 concentration (ug/m3) CF=1, standard particles
XX YY PM1.0 concentration (ug/m3) in atmospheric environment
XX YY PM2.5 concentration (ug/m3) in atmospheric environment
XX YY PM10 concentration (ug/m3) in atmospheric environment
XX YY Number of particles >0.3 um in 0.1 liter air
XX YY Number of particles >0.5 um in 0.1 liter air
XX YY Number of particles >1.0 um in 0.1 liter air
XX YY Number of particles >2.5 um in 0.1 liter air
XX YY Number of particles >5.0 um in 0.1 liter air
XX YY Number of particles >10 um in 0.1 liter air
VV Version number ?
EE Error code ?
C1 C2 Check code basically the sum of all bytes up to the check code

Data is encoded in big-endian format.

Protocol incoming data

This protocol allows commands to be sent to the module, also in frames. Each command frame consists of 7 bytes. It starts with two marker bytes, then a command byte, two data bytes and finally two checksum bytes.

Command Protocol
Value Meaning Remark
0x42 0x4D Begin marker ASCII for characters 'B' and 'M'
CC Command 0xE1, 0xE2 or 0xE4
HH LL Data Depends on command
C1 C2 Check code basically the sum of all bytes up to the check code

References

List of dust sensors:

Citizen science projects for measuring ultra fine dust:

Dust measurement blog: