open_ozone_sensor

Air quality sensor for monitoring ozone levels

Proof of concept

Components

• Arduino Nano (v3) or Uno (ATMega328)
• AM2320 - I2C Humidity and Temperature sensor ( temporary )
• Ozone2Click - SPI Ozone sensor ( based on MCP3551 and MQ131 )

Sensor wiring

MCP3551 22bit adc on SPI and AM2320 on I2C.

Arduino pin	Sensor pin
10	MCP3551 - CS
12	MCP3551 - SDO
13	MCP3551 - SCK
A4	AM2320 - SDA
A5	AM2320 - SCL

UART Protocol

// HEADER
typedef struct {
	uint8_t  firstLeadIn; // 0x55
	uint8_t  lastLeadIn;  // 0xAA
	uint8_t  packetLength;
	uint8_t  packetID;	  // 0 - error, 1 - sensor data, 2 - controller log
	uint8_t  headerCRC;	  // CRC8
} __PACKED UARTHEADER;

// SENSOR PACKET
typedef struct {
	float ozonePPM;
	float temperature;
	float humidity;
	float ratio;
} __PACKED SENSORPACK; 	  // + 2 bytes of CRC16

Prototype

Prototype sensor board should incorporate both low and high concentration versions of MQ131 ozone sensors and a precise temperature and humidity sensor. For communication there should be an easy to access BUS to allow multiple sensor nodes to connect to a network and a central controller. ( At this point MODBUS and CAN are both an option. )

With external 22 bit ADC

With internal 16 bit ADC