LamaPLC: Gas sensors

The gas sensor modules contain the additional technology required for sensor ICs (voltage regulation, pull-up resistors,…) and the connection pins simplify the connection of the sensors to, for example, Arduinos. The modules are typically universal and can be used for several sensors, so it's worth paying attention to which sensor is installed on the module, mainly because of the power supply (almost all sensors work with 3.3V, but not all of them work with 5V). There are often bridges used for addressing on the modules, which can be soldered in and out, and for example I²C addresses can be set with them.

Type of measurement	Name	Pics	Sensors	Description
CO2 TVOC	CJMCU-811		CCS811	I²C interface, address: ADDR pin low: 0x5A, ADD pin high: 0x5B VCC: normally 3.3V GND: GND SCL: Serial Clock Line, interface to I2C SDA: Serial Data Address, interface to I2C WAK: Wake (active low, not connected) INT: Interrupt (active low, not connected) RST: Reset (active low, not connected) ADD: 10k pull-down to GND, setting the I2C address to 0x5A Arduino library: ✔
gas	MQ-nnn		MQ-2 (flamable gas) MQ-3 (alcohol) MQ-4 (CH4) MQ-5 (LPG, LNG, natural gas) MQ-6 (LPG, iso-butane,..) MQ-7 (CO) MQ-8 (H2) MQ-9 (CO, CH4, LPG) MQ-135 (NH3, benzene)	Analog and digital signals Pinout for modul: VCC: normally 5V GND: GND DO: Digital (alarm) signal, by setting a threshold value using the potentiometer AO: Analog (measuring) signal, 0..5 V Pinout for sensor: H-Pins: Out of the two H pins, one pin is connected to supply and the other to ground A-B-Pins: A pins and B pins are interchangeable. These pins will be tied to the supply voltage Preheat duration minimum 20 seconds Arduino library: ✔
CO H2 Alcohol (C2H5OH) Hydrogen(H2) Formaldehyde(CH2O) Alcohol gas NO²	GRV GAS SENS V2		All 4 sensors in one platform: GM-102b (NO²) GM-302b (alcohol gas) GM-502b (Alcohol (C2H5OH), Hydrogen(H2), Formaldehyde(CH2O)) GM-702b (Carbon monoxide (CO), Hydrogen (H2))	I²C interface, default address:0x55 VCC: normally 5V GND: GND SCL: Serial Clock Line, interface to I2C SDA: Serial Data Address, interface to I2C Arduino library: ✔
Temperature Humidity CO²	SCD-30 modul		SCD-30	Pinout: - VDD: Supply Voltage (-0.3 V –6.0V) - GND: Ground - TX/SCL: Modbus: Transmission line (Push/Pull with 3V level) I²C:Serial clock(internal 45kΩ pull-up resistor, pulled to 3V, for higher voltages a level shifter is needed) - RX/SDA: Modbus: Receive line (Input must not exceed 5.5V) I²C:Serial data(internal 45kΩ pull-up resistor, pulled to3V, for higher voltages a level shifter is needed) - RDY: Data ready pin. High when data is ready for read-out - PWM: PWM output of CO² concentration measurement - SEL: Interface selectpin. Pull to VDD(do not exceed 4V, use voltage divider in case your VDD is > 4V)for selecting Modbus, leave floating or connect to GND for selecting I²C The default I²C address of SCD30 is 0x61

The easiest way to find the example program for the current sensor is in the Arduino program in the “Library Manager”.

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