1. The fault characteristics and maintenance of industrial control circuit board capacitor damage The failure caused by capacitor damage is the highest in electronic equipment, especially the damage of the electrolytic capacitor is the most common. Capacitor damage manifests itself as:  1. capacity becomes smaller; 2. complete loss of capacity; 3. leakage; 4. short circuit. Capacitors play different roles in the circuit, and the faults they cause also have their own characteristics. In industrial control circuit boards, digital circuits account for the vast majority. Capacitors are mostly used for power supply filtering and less for signal coupling and oscillation circuits. If the electrolytic capacitor used in the switching power supply is damaged, the switching power supply may not be able to vibrate and there is no voltage output; or the output voltage is not well filtered, and the circuit is chaotic due to the unstable voltage. Can not machine, if the capacitor an...

Impedance matching Impedance matching means that when energy is transmitted, the load impedance must be equal to the characteristic impedance of the transmission line. At this time, there is no reflection in the transmission, which indicates that all energy is absorbed by the load. On the contrary, there is energy loss in transmission. In high-speed PCB design, the matching of impedance is related to the quality of the signal. When do PCB traces need to be impedance matched? It does not mainly look at the frequency, but the key is to look at the steepness of the signal edge, that is, the rise / fall time of the signal. It is generally considered that if the rise / fall time of the signal (in terms of 10% to 90%) is less than 6 times the wire delay, it is high speed Signal, we must pay attention to the problem of impedance matching. The wire delay is generally set to 150ps / inch. Characteristic impedance During the propagation of a signal along a transmission line, if th...

This article introduces the communication architecture of the IoT from a macro perspective so that everyone has a preliminary understanding of the working principle of the increasingly frequent IoT devices, which are mainly divided into three modes: direct integration pattern, gateway integration pattern, and cloud integration pattern. 1. Direct integration pattern Generally, the IoT devices we use, such as the apple watch, and the mobile phone are direct connection mode, but they use Bluetooth and cannot provide a universal interface to access. The solution to this problem is to use Web technologies that have been mature for many years. So, the concept of the Web of Things was also proposed. If the device supports HTTP and TCP / IP and can directly connect to the Internet, such as using Wi-Fi, then this direct connection mode can be used. Usually, devices need more powerful processing power and have continuous power, such as smart homes. To directly control the device through...

As a carrier of various components and a hub for circuit signal transmission, PCB has become the most important and critical part of electronic information products. The quality and reliability of the PCB determine the quality and reliability of the entire equipment. However, due to cost and technical reasons, a large number of failures have occurred during the production and application of PCBs. For this kind of failure problem, we need to use some commonly used failure analysis techniques to ensure the quality and reliability of the PCB during manufacturing. This article summarizes the top ten failure analysis techniques for reference. 1. Appearance inspection Visual inspection is to visually inspect or use some simple instruments, such as stereo microscopes, metallographic microscopes, and even magnifying glasses, to check the appearance of PCBs, and to find the parts of failure and related physical evidence. The main functions are to locate failures and determine the failure...