Abstract: This paper analyzes the circuit principle and function of the power charging circuit of the ZQZ-CⅡ automatic station, and introduces the fault points in the charging circuit. This paper can serve as a reference for hardware maintenance personnel of ZQZ-CⅡ automatic stations in circuit analysis and quick fault location.
Keywords: Automatic weather station; Charging circuit; Principle; Maintenance
0 Introduction
The ZQZ-CⅡ type automatic weather station power supply charging circuit is an auxiliary device for the ZQZ-CⅡ type automatic weather station power supply. When the mains power is abnormal, it uses a storage battery for power and automatically switches to backup power. The backup power supply includes a storage battery with a capacity of 8Ah/12V, which can ensure the data logger and sensors can operate for 3 days in the event of a power outage. This ensures the normal and reliable data acquisition of the logger and has advantages such as simple design, rapid response, low cost, reliable use, and simple maintenance. It is widely used in ZQZ-CⅡ type automatic weather stations.
1. Circuit Principle
The power charging circuit of the ZQZ-CⅡ type automatic station is shown in Figure 1.
1.1 Mains Input Circuit
The mains input circuit (shared by the mains power supply and charging circuit of the automatic station) is composed of power surge protector P1, P2 bandpass filter Z and isolation transformer T1. The functions of each component are as follows: The power surge protector is a low-voltage power protection device. When the mains power generates a high pulse voltage due to lightning or other factors, the power surge protector can release a large amount of pulse energy generated by the induced lightning on the circuit to the safe ground line in the shortest time, thereby protecting the user equipment on the circuit; The bandpass filter is used to suppress the interference of the power grid from entering the collector through the power supply, and to prevent high-order harmonics and low-order harmonics on the circuit from polluting the power grid; The main function of the isolation transformer is to isolate the power supply [3] and cut off the coupling path and transmission channel of the electromagnetic interference source. The primary and secondary transformation ratio of the transformer is equal to 1. The mains ground and the circuit ground are separated, thereby effectively preventing electric shock accidents and protecting personal safety.
1.2 Transformer, rectifier, and filter circuits
The transformer, rectifier, and filter circuit consists of T2, D1 to D4, and C1. The 220V AC power is filtered by the full-bridge rectifier composed of the 14V transformer T2 and D1 to D4, and then by C1 to output approximately 15V DC power, which supplies power to the LM317.
1.3 Battery charging circuit
The battery charging circuit consists of a three-terminal adjustable voltage regulator IC LM317, an output voltage adjustment circuit (R1, R2, RP1), and protection diodes D5 and D6. C5 filters and outputs approximately 13.8V DC to power the LM317. After internal voltage regulation by the LM317 and filtering by C5, a 13.8V DC voltage is output to charge the battery. R1, R2, and RP1 form the output voltage adjustment circuit, which changes the output voltage value via RP1. D5 is a protection diode to prevent input short circuits from damaging the LM317 voltage regulator IC. D6 is used to prevent short circuits at the output of the LM317 voltage regulator IC from damaging it. C2 and C4 suppress ripple voltage. D7 is an isolation diode to prevent battery voltage feedback to the front-end voltage regulator circuit after a mains power outage, thus preventing damage to the front-end circuit. R3 is a current-limiting resistor to protect the voltage regulator IC from overcurrent [1, 2] .
2. Troubleshooting methods for common faults
2.1 The fuse blows when the plug is inserted into the mains power supply.
When the plug is inserted into the mains power, the fuse blows. Possible causes of the fault include: the surge protector P1 or P2 is short-circuited; the bandpass filter Z is short-circuited; diodes D1 to D4 in the full-wave rectifier bridge are short-circuited and broken down; the filter capacitor C1 is short-circuited or the leakage current is too large. Repair examples: (1) When the plug is inserted into the mains power, the fuse blows. After inspection, it was found that D2 in the full-wave rectifier bridge was short-circuited and replaced. The instrument returned to normal. (2) The bandpass filter Z is short-circuited. After replacement, the instrument returned to normal.
2.2 No charging voltage at both ends of the battery
There is no charging voltage at both ends of the battery. Possible causes include: damage to the three-terminal adjustable voltage regulator IC LM317; burnout of R3; short circuit of D6. Repair example: Disconnect the battery terminals and use a multimeter to measure the terminals connected to the battery. There is no voltage output. There is voltage across capacitor C5. Remove the isolation diode D7 and measure it. D7 is open circuit and faulty. After replacing D7, the output voltage is normal.
2.3 Decreased load-carrying capacity of charging circuit
A decrease in the charging circuit's load-carrying capacity leads to insufficient battery charging and a shortened battery discharge time after a power outage. Key checks include: whether the capacitance of filter capacitor C1 has decreased or whether the leakage current is excessive; whether the rectification characteristics of the diodes in the full-wave rectifier bridge have deteriorated, and whether any individual diodes are open-circuited or damaged; and whether the performance of the LM317 has deteriorated. Repair example: After a power outage, the mains battery discharge time was significantly shorter than before. Replacing the battery did not resolve the issue. Upon opening the power supply casing, inspection revealed that rectifier diode D3 in the full-wave rectifier bridge was open-circuited. Replacing it restored normal charging circuit function.
2.4 The output voltage of the charging circuit fluctuates.
If the output voltage of the charging circuit fluctuates, focus on checking the adjustable potentiometer RP1. This is usually caused by poor internal contact after prolonged use. After replacing the adjustable potentiometer, the output voltage returns to normal.
3. Conclusion
This analysis of the power charging circuit of the ZQZ-CⅡ type automatic station, including its circuit principles, functions, common fault phenomena, fault locations, and specific troubleshooting methods, enables maintenance personnel to quickly and accurately troubleshoot problems, thus ensuring the normal, reliable, and stable operation of the automatic station's data collector.
References:
[1] Lin Gang. Correct use of LM317 integrated voltage regulator circuit [N]. Electronics News, 1998-7-19 (9).
[2] Yao Xingzhong. UPS Principles and Maintenance Techniques [M]. Beijing: Science Press, 1997.
[3] Zhang Shubi. Isolation Transformer [N]. Electronic Newspaper, 2000-6-4 (11).
For details, please click: ZQZ-CⅡ Type Automatic Station Power Supply Charging Circuit Principle and Repair
