Sensors

This is a list of sensors and their related information.

MH-Z19 CO2 Sensor

These CO2 modules cost about $17 USD. They come in 3 models: 0-2000PPM, 0-5000PPM, and 0-10000PPM.

Interface: PWM or UART

See: MH-Z19 Carbon Dioxide Sensor

CCS811 Air Quality Sensor

The CCS811 air quality sensor can measure Volatile Organic Compounds (VOCs). These cost about $8 USD.

Pin Number	Pin Name	Description
1	VCC	Power supply for the module can typically 3.3V is used
2	GND	Ground of the module, connected to ground of the circuit
3	SCL	Serial Clock Line, used to provide clock pulse for I2C communication
4	SDA	Serial Data Address, used to transfer the data through I2C communication
5	WAK	Wake (active low)
6	INT	Interrupt (active low)
7	RST	Reset (active low)
8	ADD	Single address select bit to allow alternate address to be selected

DHT 11, DHT22

The DHT11 is a digital temperature and humidity sensor. They are notable by their blue perforated plastic package. The DHT11 is created by Aosong Guangzhou Electronics Co. Ltd. Each unit costs around $1.5 USD.

The DHT22, also called AM2302, RHT03, is similar to the DHT11 but offers a slightly wider operating temperature range and higher temperature and humidity resolution. The DHT22 is slightly more expensive at around $3 USD per unit.

The difference between the two modules are outlined in the table below.

	DHT11	DHT22
Relative Humidity Operating Range	20 ~ 90%	0 ~ 100%
Relative Humidity Accuracy	±5%RH	±2%RH (Max ±5%RH)
Humidity Resolution	1%RH	0.1%RH
Humidity Repeatability	±1%RH	±1%RH
Humidity Hysteresis	±1%RH	±0.3%RH
Long-term Stability	±1%RH/year	±0.5%RH/year
Temperature Operating Range	0 ~ 50°C	-40 ~ 80°C
Temperature Accuracy	±2°C	±0.5°C
Temperature Resolution	1°C	0.1°C

BMP085, BMP180, BMP280

These BMPs are atmospheric pressure sensors. They use I2C or SPI. The BMP280 appears to have superseded and are readily available on Ebay for around $0.50 and $1 USD each.

MAX30102

The MAX30102 is a heart rate monitor and pulse oximeter biosensor. These modules cost about $2 USD on AliExpress.

HC-SR501 Infrared Motion Sensor

The SR501 is an infrared motion sensor. They cost around $1.5 USD each. It has 2 potentiometers that are used to adjust the detection sensitivity and duration of the signal. The middle output pin gives a 3.3V signal when motion is detected and resets back to ground after a period of time.