Water Level Sensor based on a New Design Structure for Irrigation Water Measurement

The objective of this study was to design a new water level sensor for irrigation water measurement to reduce the investment of water measuring equipment required for agriculture management. Based on ultrasonic pulse-echo technology, a new hardware structure including an ultrasonic transmission circuit, echo receiver circuit, data output circuit and micro control unit (MCU) were described in this paper. A specially designed pulse transformer and a drive circuit based on the NEC555 were used to improve the driving capability for ultrasonic transducers. A low cost but has a high quality for accepting circuit was adopted based on Sony Corporation's infrared demodulator, CX20106A. Output circuit which based on the RS232 interface using multichannel RS-232 Drivers-Receivers MAX232 was used to output the dates, this circuit is simple and easy to extend. In addition, an IC card (corn is 64K SPI Bus Serial EEPROM, AT24C64) based correction parameters input circuit was adopted. Furthermore, some factors, such as temperature, water surface fluctuation and process response time etc. which influence accuracy were discussed. Then, the corresponding corrections methods not only include hardware methods but also include software methods were proposed. A temperature detection module which based on a digital sensor, the Dallas Semiconductor™ DS18B20, was added to the hardware systems. At the same time, in order to reduce the process response time of program written in C51 language in the MCU control system, the integration programming technology using C51 language and assembler language was used. Besides, voltage conversion and power supply circuits based on three-port voltage regulator circuit LM7805 and LM7808 was designed. The test result shows that this design has a high accuracy and stability. It is possible to get water level data with small errors, and this design reduces the production cost.