Panasonic-SN-GCJA5

Introduction

Micropython driver for Panasonic SN-GCJA5 particulate matter (PM) sensor. Tested on Raspberry Pico W
Port from sngcja5 The sensor updates all registers every second.

Wiring

Panasonic SN-GCJA5 uses JST SM05B-GHS-TB(LF)(SN) connector and requires 3.3V and 5V for direct wiring. Fortunately, Raspberry Pi GPIOs are 3.3V by default and also supports dual power supply voltages, 3.3V and 5V. Please refer to sensor specification sheet and table below for wiring guide.

Sensor Connector Pin	Symbol	Recommended Voltage	Description	RPico Physical Pin	RPi I/O
Pin 1	TX	3.3V	UART TX (unused if using I2C protocol)	not connected
Pin 2	SDA	3.3V	I2C Data	Pin 1	GP0 (I2C0 SDA)
Pin 3	SCL	3.3V	I2C Clock	Pin 2	GP1 (I2C0 SCL)
Pin 4	GND	0V	Ground	Pin 38	Ground
Pin 5	VDD	5V	Power supply	Pin 40	5v Power

More details about Raspberry Pico pinout

Status register

The Panasonic SN-GCJA5 has a proprietary logic capable of monitoring the status of critical parts and compensating with software correction in order to maintain a certain level of performance during the lifetime (expected lifetime of 5 years at 25°C, 60%RH on continuous current).

pm_sensor.get_status_data()
{'status_register': '00000000'} 

Particle Detect status [bit5][bit4]

0. Normal status
1. Normal status (within -80% against initial value), with S/W correction
2. Abnormal (below -90% against initial value), loss of function
3. Abnormal (below -80% against initial value), with S/W correction

LED operational status [bit3][bit2]

0. Normal status
1. Normal status (within -70% against initial LOP), with S/W correction
2. Abnormal (below -90% against initial LOP) or no LOP, loss of function
3. Abnormal (below -70% against initial LOP), with S/W correction

PWM Fan operational status [bit1][bit0]

0. Normal status
1. Normal status (1,000rpm or more), with S/W correction
2. In initial calibration
3. Abnormal (below 1,000rpm), out of control

Overall sensor status [bit7][bit6]

0. everything is fine, thanks, I appreciate your interest
1. Abnormal status for any one of Particle detect, LED, PWM statuses
2. Abnormal status for any two of Particle detect, LED, PWM statuses
3. Abnormal status for any three of Particle detect, LED, PWM statuses

Examples

from machine import Pin, I2C
from picosngcja5 import SNGCJA5


# If SDA and SCL are connected to I2C bus 0, then:
i2c = I2C(0, sda=Pin(0), scl=Pin(1))
pm_sensor = SNGCJA5(i2c)



# The get_measurement method returns a dictionary of all measurement value 
result = pm_sensor.measure()

print(result)
'''
    Structure of result
    {
    'mass_density': {
        'pm10': <float>,
        'pm2.5': <float>,
        'pm1.0': <float>
        }, 
    'particle_count': {
        'pm1.0': <float>, 
        'pm10': <float>, 
        'pm7.5': <float>, 
        'pm2.5': <float>, 
        'pm5.0': <float>, 
        'pm0.5': <float>
        }
    }
'''

Dependencies and Installation Instructions

copy the library in your project and import it

Limitation

Currently, this driver only supports I2C protocol