Experience in hardware

I. PCB design

PCB design plays an important role in electronic design. The quality of the circuit also determines the stability of the circuit. I am not going to introduce any tips here. I just want to talk about some details that are often ignored in the general process of using dxp to make a PCB.

Before generating a PCB, we must first ensure the correctness of the schematic diagram. If the schematic diagram is not correctly connected, the subsequent components will be useless. When I draw a diagram of the principle, I feel that it is best to use the package I have drawn. Generally, components have self-contained packages, but those packages may not be very good for us, mainly for the pad, the size is not suitable. It will be a waste of time to modify the PCB after it is generated.

After the PCB is generated, it is best to set the line width and safe distance before layout and wiring. If these are not set at the beginning, it may be a bit difficult to make the Board later, because we are making the Board ourselves now, and in the process of transfer and corrosion, some circuits may be damaged. If the line is too small, it is easy to open circuit. If the safe distance is too close, it is easy to short circuit, in addition, these problems will cause you a lot of trouble when you detect the circuit, especially during the competition, the time is relatively tight, and it will not be easy to detect at that time.

Usually, a single panel can meet the requirements, but sometimes it also uses dual panels (such as SMD chips with more discipline). When doing dual panels, it is mainly to do a good job of positioning, make sure that the upper and lower welding holes are aligned. Otherwise, the plate will be scrapped. When transferring data, first transfer one side, and then play a few positioning holes, because the positioning holes may cause damage to the welding disc, so the positioning holes should be accurate and appropriate, do not play too much. When selecting the positioning hole, try to use the welding holes that pass through the hole or do not walk the line above, or you can put a few pad in the blank or laying the ground when doing the PCB as the positioning hole. In every step of making a board, you must do it carefully. Do not leave hidden risks. Otherwise, it will be very troublesome to check the circuit.

Ii. Circuit Maintenance

Inspection of Operational Amplifier Circuit

No output signal or incorrect output.

1. ensure the correctness of the schematic diagram (the schematic diagram is correct) and the proper parameters of each component. If the schematic diagram is incorrect, you cannot check the result.

2. Check whether the power supply is connected. This is not always the case, but when you have a circuit problem and are eager to solve the problem, this problem will often occur along with it, which may cause unnecessary trouble.

3. Check whether the output is transient. The plate we usually make is very easy to short circuit or open circuit, there is also the welding hole, sometimes the welding hole is too small, we often use things to drill, after drilling, cracks may occur between the Solder Pad and the circuit, leading to Broken Circuit. This should be checked carefully. Sometimes the Broken Circuit is only a small crack, so you cannot pay attention to it. Check whether the connection between each node and the circuit is normal with the Ohm of the multimeter.

4. Virtual soldering. This is also very difficult to find. When checking this, it is basically the same as in "3". This part can be checked basically during the Third-step check. The main reason for virtual soldering is pin oxidation. What is most likely to happen is the overlay hole of the double panel we made. Secondly, during the welding of some chip patches, it is very easy to perform virtual welding and transient welding. During the welding process, we must pay attention to it and try to eliminate the problem in the initial stage, otherwise, troubleshooting will be a waste of time.

It is very important to ensure the electrical conductivity of wires in general circuits connected by wires. Especially in some signal circuits, sometimes the disconnection of a line does not affect the indicator light or other visible channel signs, but the circuit cannot work normally, but it can be used in the past, there are only two possibilities: 1. The components are burned out; 2. the wires are broken. The wires are usually broken at two ends. Pay attention to this inspection.