The design of CO gas monitor based on TC35 GSM module is mainly characterized by the application of SMS for data transmission. The wireless communication module TC35 is introduced in detail, and the application of tcc35 short message transceiver module in CO gas monitor is given. CO gas concentration monitor is a portable intelligent instrument used to measure CO content in relevant ambient air. At present, the most common way of data communication between domestic CO gas monitor and control center is through CAN bus, RS485 bus or RS232 bus. The communication distance of RS232 bus is 12 m, the maximum is 15.4 m; the communication distance of RS485 bus is 1200 m. The direct communication distance of CAN bus is up to 10 km. But no matter which way, there is a distance limit, and ultimately determines the fixity of the control center. With the rapid popularization of GSM mobile communication network and the increasingly fierce competition, GSM module, as a main GSM network access device, has been applied more and more widely, and has developed a variety of promising applications.

TC35 module is the main functional component of the terminal, which is composed of GSM baseband processor, power ASIC, RF circuit and flash memory. It is responsible for processing the audio, data and signal in GSM cellular equipment, and the embedded software performs the functions of application interface and all GSM protocol stations. Baseband processor includes all analog-to-digital conversion functions of cellular wireless part. In order to meet the growing requirements of GSM and PCs cellular user market, it can support fr, HR and EFR voice and channel coding without external circuit. The RF part is based on smarti circuit. The antenna cable in the module is connected to GSC type 50 Ω connector. TC35 module is suitable for minimum power GSM cellular equipment. The application part of this kind of cellular equipment constitutes man-machine interface (MMI). TC35 can be accessed through serial port (RS232). TC35 is connected to the cellular application part through a 40 pin ZIF. The ZIF connector provides application interfaces for control data, audio signal and power cable. The operating voltage of the terminal system is 5 VDC. Since the peak value of TC35’s sudden power consumption current can reach 3 A, the external voltage regulator must be sufficient to provide the rated current. In this terminal. Lm2596 switching power supply is used to complete the conversion from 12V to 5V as the power supply of TC35 terminal. It must be noted that. Lm2596 needs high-power inductors and capacitors to complete the switching power supply conversion, so as to improve the energy storage capacity and meet the power consumption requirements of TC35.

Hardware circuit of TC35 wireless gas testing system

Structure of CO gas monitor system

The structure of portable CO gas concentration monitor with GSM short message sending and receiving function is shown in the figure. The monitor developed by the author is mainly used to monitor the concentration of CO in the air of public places and some production workshops. The battery is used as the power supply. The CO sensor N1 is nap-505 electrochemical sensor produced by Japan fundamental special chemical Co., Ltd. The output current of the sensor is linear with CO concentration. A1 (op90) can ensure the equipotential of working electrode and reference electrode. The output current of O μ a ~ 70 μ A is converted into 0 V ~ o.7 V voltage by AA (op90) to ensure the output voltage of A3 is 0 V ~ 2.5 V when CO concentration is 0 “10-3, so as to meet the input requirements of MD converter u.i (ADS7822). The op90 has an internal zeroing circuit that allows the instrument amplifier to provide true zero input and zero output operation. The temperature characteristic of nap-505 is compensated by NTC thermistor with constant B of 3 435 K. after temperature compensation, its output can meet the accuracy requirement in the range of – 10 ℃ “50 ℃.

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