Deliver accurate and swift identification of ethanol presence using 3SP-Ethanol-1000 and PIC18F57Q43

Alcohol 2 Click is based on the 3SP-Ethanol-1000 from SPEC Sensors, which can sense ethanol concentration up to 1000ppm. The sensor has a very short response time; however, the longer it is exposed to a particular gas, the more accurate data it can provide. This is especially true when calibration is performed. The sensor is sensitive to small dust particles, condensed water, and other impurities, which might prevent gas from reaching the sensor. It is advised to protect the sensor when used in critical applications. In ideal conditions, the lifetime of this sensor is indefinite, but in real-life applications, the expected operating life is more than five years (10 years at 23 ± 3 ˚C; 40 ± 10 %RH). Although very reliable and accurate, this sensor is great for building relative gas sensing applications. For example, it can detect increased levels of ethanol gas. However, when developing applications for the absolute gas concentration, the sensor must be calibrated, and the measurement data needs to be compensated. Factors such as humidity and temperature can affect measurements; the sensor reaction curve to a specific measured gas (ethanol in this case) is not completely linear, and other gases might affect the measurement (cross-sensitivity to other gases). For this reason, a range of calibration routines must be done in the working environment conditions to calculate the absolute

gas concentration. Alcohol 2 click uses the LMP91000, a configurable AFE potentiostat IC for low-power chemical sensing applications, from Texas Instruments. It provides the complete sensor solution, generating the output voltage proportional to the sensor current. A trans-impedance amplifier (TIA) with a programmable gain is used to convert the current through the sensor, covering the range from 5μA to 750 μA, depending on the used sensor. The voltage between the referent electrode (RE) and the working electrode (WE) is held constant, with the bias set by the variable bias circuitry. This type of sensor performs best when a fixed bias voltage is applied. The sensor manufacturer recommends a +100mV fixed bias for the sensor on this Click board™. The bias voltage and the TIA gain can be set via the I2C registers. In addition, an embedded thermal sensor in the AFE IC can be used for the result compensation if needed. It is available via the VOUT pin as the analog voltage value with respect to GND. The Click board™ has two additional ICs onboard. The first is the MCP3221, a 12-bit successive approximation register A/D converter from Microchip. The second IC is the OPA344, a single-supply, rail-to-rail operational amplifier from Texas Instruments. It is possible to use the onboard switch, labeled as AN SEL, to select the IC to which the VOUT pin from the

LMP91000 AFE is routed. If the switch is in the ADC position, the VOUT pin will be routed to the input of the MCP3221 ADC. This allows the voltage value at the VOUT pin to be read via the I2C interface as digital information. When the switch is in the AN position, it will route the VOUT pin of the LMP91000 AFE IC to the input of the OPA344. The output of the OPA344 op-amp has a stable unity gain, acting as a buffer so that the voltage at the VOUT pin of the AFE can be sampled by the host MCU via the AN pin of the mikroBUS™. The RST pin on the mikroBUS™ is routed to the MEMB pin of the LMP91000, and it is used to enable the I2C interface section, thus making it possible to use more than one chip on the same I2C bus. When driven to a LOW logic level, the I2C communication is enabled, and the host device (host MCU) can issue a START condition. The RST pin should stay at LOW during the communication. This Click board™ can operate with either 3.3V or 5V logic voltage levels selected via the VCC SEL jumper. This way, both 3.3V and 5V capable MCUs can use the communication lines properly. Also, this Click board™ comes equipped with a library containing easy-to-use functions and an example code that can be used as a reference for further development.

PIC18F57Q43 Curiosity Nano evaluation kit is a cutting-edge hardware platform designed to evaluate microcontrollers within the PIC18-Q43 family. Central to its design is the inclusion of the powerful PIC18F57Q43 microcontroller (MCU), offering advanced functionalities and robust performance. Key features of this evaluation kit include a yellow user LED and a responsive

mechanical user switch, providing seamless interaction and testing. The provision for a 32.768kHz crystal footprint ensures precision timing capabilities. With an onboard debugger boasting a green power and status LED, programming and debugging become intuitive and efficient. Further enhancing its utility is the Virtual serial port (CDC) and a debug GPIO channel (DGI

GPIO), offering extensive connectivity options. Powered via USB, this kit boasts an adjustable target voltage feature facilitated by the MIC5353 LDO regulator, ensuring stable operation with an output voltage ranging from 1.8V to 5.1V, with a maximum output current of 500mA, subject to ambient temperature and voltage constraints.