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RAK12009 WisBlock MQ3 Alcohol Gas Sensor Module Datasheet

Overview​

Description​

The RAK12009 is an Alcohol Gas Sensor module, part of the RAKWireless WisBlock Sensor Series. The sensor used in this module is the MQ-3B from Zhengzhou Winsen Electronics. This sensor is capable of detecting alcohol gas in the air with an alcohol concentration detection range of 25 to 500 ppm.

Features​

  • MQ-3B Alcohol Gas Sensor
  • Alert Function
  • I2C Interface, 7-bit I2C Address: 0x54
  • Detection Range: 25 to 500 ppm (Alcohol Gas)
  • 3.3 V or VBAT Power Supply
  • Chipset: Winsen MQ-3B
  • Module size: 25 x 35 mm

Specifications​

Overview​

Mounting​

The RAK12009 WisBlock MQ3 Alcohol Gas Sensor Module can be mounted to the IO slot of the WisBlock Base board. Figure 1 shows the mounting mechanism of the RAK12009 on a WisBlock Base module.

Figure 2377: RAK12009 WisBlock MQ3 Alcohol Gas Sensor Mounting

Hardware​

The hardware specification is categorized into five parts. It shows the chipset of the module and discusses the pinouts of the module and its corresponding functions and diagrams. It also covers the electrical and mechanical parameters that include the tabular data of the functionalities and standard values of the RAK12009 WisBlock MQ3 Alcohol Gas Sensor Module.

Chipset​

VendorPart number
WinsenMQ-3B

Pin Definition​

The RAK12009 WisBlock MQ3 Alcohol Gas Sensor Module comprises a standard WisBlock connector. The WisBlock connector allows the RAK12009 module to be mounted to a WisBlock Base board. The pin order of the connector and the pinout definition is shown in Figure 2.

NOTE
  • I2C related pins, ALERT, EN, VBAT, 3V3, and GND are connected to WisConnector.
  • VBAT is the battery voltage input, max voltage is 4.2 V.
Figure 2378: RAK12009 WisBlock MQ3 Alcohol Sensor Pinout

Electrical Characteristics​

Recommended Operating Conditions​
SymbolDescriptionMin.Nom.Max.Unit
VBATSupply Voltage2.8-4.2V
VCCIODigital IO Power Supply-3.3-V
VCCADC to I2C Chip Power Supply-5-V

Mechanical Characteristics​

Board Dimensions​

Figure 3 shows the dimensions and the mechanic drawing of the RAK12009 module.

Figure 2379: RAK12009 WisBlock MQ3 Alcohol Sensor Module Mechanic Drawing
WisConnector PCB Layout​
Figure 2380: WisConnector PCB Footprint and Recommendations

Schematic Diagram​

Power Supply Circuit​

Figure 5 shows RAK12009 step-up power supply circuit.

  • VBAT Battery voltage (max voltage is 4.2 V)
  • EN Power enable pin (active high). This pin is connected to IO6 of WisBlock Core.
Figure 2381: RAK12009 WisBlock MQ3 Alcohol Sensor Module Power Supply
Alcohol Detector Circuit​

Figure 6 shows the alcohol detector circuit.

  • U2 is the MQ-3B Alcohol sensor.
  • The pin 2 voltage (5 V) is used to supply standard working temperature to the sensor.
  • AOUT is the voltage of load resistance R12 which is in series with sensor.
  • The pin 1 and pin 3 voltage (5 V) supply the detect voltage to load resistance R12.
  • U3 is a 12-bit analog-to-digital converter with alert function. The U3 power supply is 5 V.
Figure 2382: RAK12009 WisBlock MQ3 Alcohol Sensor Module Detector Circuit
Voltage Level Shifter Circuit​

The 40-pin WisConnector voltage level is 3.3 V, while U2 and U3 levels are 5 V. To interface the different voltage levels between 40-pin WisConnector and Alcohol detector circuit, the RAK12009 uses a built-in voltage level shifter circuit.

Figure 2383: Voltage Level Shifter Circuit
I2C Address​

The I2C address of the Analog-to-Digital converter chip of RAK12009 can be selected via resistor jumpers, as shown in Figure 8.

Figure 2384: RAK12009 Alcohol Sensor Module I2C Address configuration

The I2C address is configured by the ADR1 and ADR0 address selection inputs, as shown below.

ADR1ADR0Slave Address [A6-A0]
FloatingFloating1010000
FloatingGND1010001
FloatingVA1010010
GNDFloating1010100
GNDGND1010101
GNDVA1010110
VAFloating1011000
VAGND1011001
VAVA1011010
NOTE
  • The default 7-bit I2C address is 1010101 = 0x55. The selection input is ADR1 and ADR0 resistor jumper connected to GND.
  • VA is U4 ADC121C021 Analog Power Supply (+5 V).
Full Schematic​
Figure 2385: RAK12009 complete schematic
J2 Connector Pinout​

RAK12009 has an additional J2 connector to provide an extra interface to the module. This connector separates the sensor module from the WisBlock Base, to fits with maker requirements. The pinout of J2 connector is shown in Figure 10.

Figure 2386: J2 Connector Pinout
WisConnector​

Figure 11 shows the 40-pin WisConnector connection.

  • VBAT is a battery voltage pin.
  • I2C1_SDA and I2C1_SCL are the I2C related pins.
  • EN is a power enable pin.
  • ALERT is an analog-to-digital converter alert pin.
Figure 2387: RAK12009 Module 40-pin WisConnector