PMSA003A Dust Sensor

PMSA003A dust sensor

The PMSA003A dust sensor can be found on Ebay for around $20 USD. Based on the datasheet, it is a laser based sensor that is capable of measuring particles as small as 0.3 micrometers.

Related and probably older dust sensors in this family include the PMS7003, PMS5003, and PMS1003.

Usage

The PMSA003A uses a 1.27mm 10 pin header. This header is smaller than the usual DIP header (those are 2.54mm). Be aware that some sellers do not sell the sensor with an adapter board or the female header which makes using this module incredibly hard to do if you don't have this header.

PMSA003A Pinout

Pinout

The pinouts for the unit I received appears to be different from the one described on the CityOS-air docs (which only lists 8 pins). Based on what I can find, here are the pinouts for this 10-pin model:

Pin	CityOS Docs	Description
1	Vcc	Pin 1 is the pin one closest to the corner
2	Vcc	Do a continuity test to confirm the orientation. It should be the one below pin 1. See picture above.
3	Gnd
4	Gnd
5	Reset	Module reset signal / TTL level @ 3.3V (reset when high, you can leave it not connected)
6	NC
7	RX	Serial receiver pin / TTL level @ 3.3V (not really useful since there're only 2 commands you can send)
8	NC
9	TX	Serial transmission pin / TTL level @ 3.3V
10	Set	Set/enable pin / TTL level @ 3.3V (high to activate, low to suspend)

Interfacing with the module

As a quick test, I connected the PMSA003A to a Raspberry Pi using the following pinout:

Function	PMSA003A	Raspberry Pi
5V	1	2 (5v)
Ground	2	6 (Ground)
Serial transmit	9	10 (UART0 RX)
Enable pin (set high)	10	7 (GPIO 4)

Set /dev/ttyAMA0 to 9600 baud with stty -F /dev/ttyAMA0 9600. You can then read the data coming in from the sensor with cat /dev/ttyAMA0.

The GPIO pin can be set up with by exporting it: echo 4 > /sys/class/gpio/export and then setting the direction: echo out > /sys/class/gpio/gpio4/direction.

To get data, toggle the GPIO 4 pin on: echo 1 > /sys/class/gpio/gpio4/value. This takes a short while (30 seconds?) for the fan to spin up and the measurement be read and returned. Toggle off the sensor again with echo 0 > /sys/class/gpio/gpio4/value.

Reading the serial data

The data sheet outlines what a data packet looks like. In summary, the structure of a payload is:

Description	Offset	Length	Comment
Start header	0	2 bytes	0x42 0x4d (ASCII "BM")
Frame length	2	2 bytes	Frame length=2*13+2(data+check bytes)
PM1.0 concentration (μ g/m3)	4	2 bytes	CF=1，standard particle
PM2.5 concentration (μ g/m3)	6	2 bytes	CF=1，standard particle
PM10 concentration (μ g/m3)	8	2 bytes	CF=1，standard particle
PM1.0 concentration (μ g/m3)	10	2 bytes	under atmospheric environment
PM2.5 concentration (μ g/m3)	12	2 bytes	under atmospheric environment
PM10 concentration (μ g/m3)	14	2 bytes	under atmospheric environment
>0.3um	16	2 bytes	number of particles with diameter beyond 0.3 um in 0.1 L of air.
>0.5um	18	2 bytes	number of particles with diameter beyond 0.5 um in 0.1 L of air.
>1.0um	20	2 bytes	number of particles with diameter beyond 1.0 um in 0.1 L of air.
>2.5um	22	2 bytes	number of particles with diameter beyond 2.5 um in 0.1 L of air.
>5.0um	24	2 bytes	number of particles with diameter beyond 5.0 um in 0.1 L of air.
>10.0um	26	2 bytes	number of particles with diameter beyond 10.0 um in 0.1 L of air.
Reserved	28	2 bytes	Reserved
Check code	30	2 bytes	Check code is computed by adding all values into two bytes

The module seems to print 'x's when no data is available or when it's not ready. So long as you are reading for the 'BM' header, the next 30 bytes should be data.

See Also

• Datasheet: https://www.evelta.com/content/datasheets/PMSA003%20series%20data%20manual_English_V2.5.pdf

• https://cityos-air.readme.io/docs/pms1003-digital-laser-dust-sensor-pm25-and-pm10
• https://cassiopeia.hk/laserdust/