Realization of Gas Sensor Measurement Application Design with Fukang HY16F184

1. Introduction

In recent years, due to the increasingly serious environmental pollution and industrial demand, the development of sensors has received much attention. Today, with the increasing complexity of air pollution prevention and the urgent need in the industry, high-performance gas sensors are gaining more and more attention. Metal oxide semiconductor (MOS)-based gas sensors have good heat resistance and corrosion resistance, fast response rate, easy component fabrication, and easy integration with microprocessors into gas sensing systems or portable monitors. Therefore, it is widely used in home and factory environments to detect toxic gases and burn explosive gases. This article will introduce the HY16F184 built-in high-precision Sigma-Delta 24 Bit ADC with CCS801 CMOS Sensor to implement a Gas Sensor application circuit. On the Gas Sensor application circuit in this article, the main components are: gas sensor (CCS801 Gas Sensor), ADC and MCU control chip. Kang and hung on-chip high-precision control HY16F184 Sigma-delta 24 Bit ADC, PGA and programmable multi-stage amplified voltage output function, can be greatly simplified PCB peripheral circuits, precision completed shifts from analog to digital.

Herein Gas Sensor application circuit is built by the precise amount of the ADC chip hung Kang HY16F184 sensed resistance change amount in the RS CCS801 CMOS Sensor, and mix thoroughly algorithm CCS801 CMOS Sensor C Library provided, can be converted to the corresponding PPM Concentration value. The small amount of current change (RH_Current) on the Heater circuit can also be measured using the HY16F184 built-in ADC. This article also provides a GUI software interface to output real-time PPM and RS and RH_Current data changes through I2C communication. The I2C to USB bridge is used to connect to the computer, and the computer-side GUI performs real-time three-channel data change display.

2. Principle description

2.1. Measurement principle

The CCS801 Gas sensor semiconductor gas sensing material changes the RS resistance when detecting gas, as shown in Figure 1. This situation is mainly caused by the detection of combustible gases such as carbon monoxide (CO) and various volatile organic compounds (VOCs) reacting with negatively charged oxygen ions adsorbed on the semiconductor oxide. When the air detects a flammable gas, the RS resistance changes, and the voltage across the RS can be measured. Typical RS resistance values ​​range from 100k to 2M ohms. RH resistors are temperature response resistors. When a Gas Sensor has a current loop through Heater+ and Heater GND, it can be regarded as a heating phenomenon, with the Heater temperature. Changes, the resistance of the RH terminal will also change, the typical RH resistance range is between 20 and 100 ohms.

Figure 1 CCS801 CMOS Sensor

2.2. Gas Sesnor Application Circuit Basic Architecture

The basic architecture of Gas Sensor in this paper is shown in Figure 2, including a gas sensor (CCS801 Gas Sensor), PMOS NX2301, ADC and MCU single chip. The HY16F184 can output PWM to control the PMOS NX2301 as current switch control. When the PWM output is High, the PMOS is turned off, which saves power and does not flow current through the Heater terminal. When the PWM output is Low, the PMOS is turned on, and a current flows through the Heater terminal. At this time, the Gas Sensor heating operation is started, and when the Gas Sensor is reheated, the power consumption is relatively high. The circuit application architecture of this paper is to use PWM to do the overall consumption current power control, set the PWM output period to 97us, the PWM output Low time is 57us and the PWM output High time is 40us. The output duration of PWM On is 100ms. At this time, it is the heating time of CCS801. After that, the PWM Off time is 400ms. When PWM Off, the output will remain High, and the cycle will be controlled by 500ms as a control cycle. PMOS NX2301 The switch acts as a control for the Heater. For a detailed PWM control time chart, refer to Figure 3 below. In addition to using PWM to do PMOS switch control to achieve power consumption control and power saving design, HY16F184 also uses high-precision ADC to do RS and RH_Current variation measurement, and the extracted data can be output by I2C. Read, detailed HY16F184 ADC specifications can refer to Figure 4 below.

Figure 2 HY16F184 Gas Sensor basic architecture diagram

Figure 3 HY16F184 PWM output control timing diagram

2.3. Control chip

Introduction to MCU: HY16F Series 32-bit High Performance Flash MCU (HY16F184)

Figure 4 纮康 HY16F series 32-bit high performance Flash microcontroller (HY16F184)

(1) Adopt the latest Andes 32-bit CPU core N801 processor.

(2) The voltage operation range is 2.4~3.6V, and the operating temperature range is -40°C~85°C.

(3) Support external 16MHz quartz oscillator or internal 20MHz high precision RC oscillator,

With a variety of CPU operating frequency switching options, users can achieve optimal power saving planning.

(3.1) Operating mode 350uA@2MHz/2 (3.2) Standby mode 10uA@32KHz/2 (3.3) Sleep mode 2.5uA

(4) program memory 64KBytes Flash ROM

(5) Data memory 8KBytes SRAM.

(6) BOR and WDT function to prevent CPU crashes.

(7) 24-bit high accuracy ΣΔ ADC analog to digital converter

(7.1) Built-in PGA (Programmable Gain Amplifier) ​​up to 128 times magnification.

(7.2) Built-in temperature sensor TPS.

(8) Ultra low input noise operational amplifier OPAMP.

(9)16-bit Timer A

(10) 16-bit Timer B module with PWM waveform generation function

(11) 16-bit Timer C module with digital Capture/Compare function

(12) Hardware serial communication SPI module

(13) Hardware serial communication I2C module

(14) Hardware serial communication UART module

(15) Hardware RTC clock function module

(16) Hardware Touch KEY function module

(17) Sigma-delta 24 Bit ADC ENOB & RMS Noise

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