Design of water temperature remote control and telemetry system based on single chip microcomputer C8051F040

   IntroductionTemperature    remote control and telemetry is a remote measurement and control of temperature, which is particularly suitable for those places where the environment is harsh and the measurement personnel are not easy to approach. In recent years, it has been widely used in industrial and agricultural production. According to the characteristics of the remote control and telemetry system, a design scheme for water temperature remote control and telemetry is proposed.

   
    The temperature remote control and telemetry system is mainly composed of a microprocessor system, a temperature measurement module, a heating module, a communication module, a liquid level module, and a host computer software. The system structure is shown in Figure 1.

    After the temperature measurement module measures the liquid temperature, it sends the temperature value to the microprocessor. When the temperature change reaches a certain value, the heating module starts heating. First, it can heat to the set temperature within the set time and stabilize at this temperature for a period of time. The system realizes telemetry and remote control through two communication modules. After the host computer sets the temperature parameters, it is transmitted to the remote microprocessor through the communication module. The microprocessor controls the heating module to heat according to the temperature set by the host computer. At the same time, the microprocessor transmits the liquid temperature and liquid level to the host computer software through the communication module. The liquid temperature and height can be displayed and monitored in real time through the host computer software interface. The display module displays the system's temperature, height and other data in real time on the LCD screen.

   Hardware Design
   The system hardware is mainly composed of C8051F040 single-chip microcomputer minimum system, PTR2000 wireless communication module, TCA785 phase-shift voltage regulation control module, Ptl00 temperature measurement module, WDK505 liquid level measurement module, etc.

1 C8051F040 MCU Minimum System

   The minimum system is based on the single-chip microcomputer C8051F040, including crystal oscillator circuit, reset circuit, anti-interference circuit, voltage reference circuit and power supply. The C8051F040 single-chip microcomputer is a fully integrated mixed-signal system-level core SoC produced by Cygnal Corporation of the United States. It has 64kB Flash, 4352BRAM, CAN controller 2.0, two serial interfaces, 5 16-bit timers, 12-bit A/D converter, 8-bit A/D converter and 12-bit D/A converter, etc. It also has a JTAG interface inside, making debugging very convenient.

2 PTR2000 wireless communication module 

  The device combines reception and transmission into one, and its operating frequency is the internationally used digital transmission frequency band of 433MHz. It adopts FSK modulation/demodulation, can directly enter data input/output, and has strong anti-interference ability. The template block integrates high-frequency reception, PLL synthesis, FSK modulation/demodulation, parameter amplification, power amplification, channel switching and other functions. The communication distance can meet the design requirements. In the design circuit, one part of PTR2000 is connected to the computer serial port after level conversion through MAX232, and the other part is connected to the minimum system.

3 TCA 785 phase-shift voltage regulation control module

   The heating module is implemented using a phase-shift trigger integrated trigger. The trigger TCA785 has a high ability to identify zero-crossing points, a wider phase-shift range, and better uniformity of the output pulse, which can make the controlled element change steplessly from 0V to 220V. It is often used under conditions with high precision requirements and harsh controlled environments. Phase-shift triggering achieves voltage regulation by changing the voltage-adjusting conduction angle. The voltage and average power across the load change with the change of the phase-shift trigger angle. In each positive or negative cycle of the thyristor, there is a part that remains on and off, that is, the output is continuously adjustable and can adapt to loads of various properties. This system sets a master control switch for the heating unit. The upper computer can directly control the on and off of the switch and use a light bulb to display the switch status. The control schematic is shown in Figure 2.

4 Ptl00 temperature measurement module 

  The Ptl00 temperature sensor is a positive temperature coefficient thermistor sensor with the advantages of vibration resistance, good stability, high accuracy and high pressure resistance.

5 WDK505 liquid level measurement module

   The WDK505 pressure transmitter is used to measure the liquid level. The instrument has the advantages of anti-condensation, anti-lightning design, strong anti-interference ability, good long-term stability, etc. The chip is placed in a full stainless steel shell for a firm seal, good reliability and high precision.