The probe capacitor polarity needle has a head diameter of 5.8. The total length of the 7-pin and 12-pin needles is 5.

Wireless Crystal 3.2*2.5mm 3225 25M (25.000MHZ) 12PF 10PPM 20PPM 30PPM

This paper introduces a wireless meter reading terminal based on Zigbee network with MSP430F149 microcontroller as the core. The main features, hardware circuit design and software design of the terminal are elaborated. The test results show that the design has the characteristics of stable operation and high reliability, and can be widely used in wireless centralized meter reading of various water, electricity and gas meter terminals, and has a good application prospect.

Circuit principle: The core processor uses TI's MSP430F149 microcontroller. In order to achieve low power consumption requirements, the circuit uses high-speed and low-speed two crystal oscillators, and the high-speed crystal oscillator generates MCL-K with higher frequency to meet the requirements of high-speed data operation of the CPU. When the CPU is not required to work, the high-speed crystal oscillator is turned off. The low speed crystal generates a lower frequency ACLK and runs the real time clock. The calendar clock chip uses the PCF8563 from PHILIPS. This chip supports IIC bus interface, adopts low-power CMOS technology, and has a wide operating voltage range of 1.0V to 5.5V. Under 3.0V power supply conditions, the typical values ​​of operating current and sleep current are 0.25μA. It can record the century, year, month, day, week, hour, minute and second, with timing, alarm and frequency output functions. The memory uses Fudan Microelectronics FM24C04. This chip is a two-wire serial EEPROM, compatible with IIC bus interface, using low-power CMOS technology, with a wide operating voltage range of 2.2V ~ 5. SV, rated current is 1mA under 3.0V supply, and sleep current is typically 5μA. In case of power failure, the data in the memory can be saved for 100 years.

MSP430F149 has two TTL level serial interfaces on the hardware. After one SP3485 chip is converted into RS485 serial interface, it communicates with the digital energy meter connected to the bottom layer, and the other directly communicates with CC2430. The RS485 bus is supported by most of the current digital energy meters. It uses balanced transmission and differential reception to achieve communication. It has strong anti-common-mode interference capability, signals can be transmitted over kilometers, and supports multi-point data communication. The CC2430 chip conforming to the Zigbee protocol supports a TTL-level serial interface, so it can communicate with the core processor without interface conversion.

All devices in the design process of the terminal are designed with low power consumption in mind. Even with battery power, the battery can be used for at least two years. And the selected components all support 3.3V voltage, all circuits only need a single power supply to run stably. Figure 1 is a hardware schematic diagram of the terminal, omitting the power supply voltage regulator circuit, the filter circuit and some peripheral components. LED1, LED2, and LED3 in the figure are used to indicate receiving data, transmitting data, and wireless network status, respectively.