Question asks **** None
Question: Zhuo teacher, our team put encoders optocoupler isolation circuit on motor driver board, but the board found that the welding finished today encoder pulse count will not be taken back with the encoder signal beating, sometimes without encoder the case of the rotation, the number of pulses ftm will change, what this may be because of what?
The above two days of questioning, you have to answer it? of course not. Even if I am determined to discuss these issues in this case, you may not have the patience. This article will discuss common issues these questions: how not to do anything that is against all kinds of problems hardware debugging process.
**** None explain the principles recently the Internet to see such a sentence describing a technological innovation, founder of the American story in one sentence:
“
I know more, because of mistakes. "
In engineering and technology in the real ability not know how to design completion, but will know where there is a trap.
How to complete the design in the information age now basically can easily retrieve textbooks, papers, patents and exhibitions, and even many components are all designed to help providers complete. But engineering practice an important requirement is to eliminate the uncertainty as much as possible, to protect the security and stability of reliable engineering. Therefore, the design of the trap that often exists in the engineering objects that implement all aspects of the process. If every detail that there is some hidden defects, many links, it will make the final product and danger, the final commissioning costs troubleshooting process will increase.
Now, in many cases to copy someone else's program called "learning", others imitate the practice called "innovation", and that innovation is relatively easy acquisition. But this plagiarism, zero cost of failure is your ability to imitate is not effectively improved.
Theoretical knowledge can help us make fewer mistakes, but you can not put an end to the practice of engineering mistakes. "I come out to mix sooner or later have to repay," now do not make mistakes, challenges for the future will be more severe.
To sum up, the problem encountered in the previous question, if helpless, need to carefully analyze:
A. Whether the basic principles of design are now clear;
B. PCB design, production, details of whether the welding, component selection and other aspects of the follow certain standard;
C. whether the basic tool is required for debugging are equipped with: multimeters, oscilloscopes, digital power limiting, LCR table, measuring surface mount components pens, a variety of welding desoldering tools;
D. whether to develop the habit of recording and analyzing problems debugging data.
If the above issues are clear, the "analysis of the problem," the latter case, introduce common solution to the problem:
Analysis First, the basic flow of a debug circuit, the electrical inspection when rendering the circuit board itself and power connections are correct, the DC voltage can be limited by means of a stream function to power the board. If the current out of a reasonable range, or there have been the protection of the power off, check the power supply and the load, troubleshooting.
After the correct power-up, confirm the magnitude and volatility of the situation at all levels of subsystem operating voltage meets the design requirements by multimeter or oscilloscope. The system starts when viewed through the "look, smell, hearing, model" or the like. First to "see" whether the chip, capacitors, diodes, etc. or polar direction of the welding error chip pin; if the instant power "smell" smell; "Listen" is listening sound is normal work, since the transformer short-circuit and sometimes emit hum sound, sound emitted from the device should not abnormal sound or the like; "touch" device is a hand to probe the temperature is too high or too cold. Some power devices, working together will be hot, but it is the result feels cool, not hot device is very hot, it also shows is not working properly.
2, sequentially checked from input to output in accordance with the inspection subsystem cascade connection relationship according to the logic design system according to the relation of series and parallel subsystems.
First static, dynamic again. To locate the fault location can be used to confirm correct false given a dummy load on the subsystem isolation, to confirm whether there is an abnormality. When abnormality occurs later in the overall test system is analyzed and then returns to this step, isolation subsystem (device) to confirm the fault to prevent the phenomenon.
3, the actual working conditions test circuitry connected to the actual load, the actual reference signal, the actual test, each test meets the design specifications
4, aging (extreme) test for various input signal port, the need to test the limits of the respective input; the output port, the respective test and burn limit state according to the output voltage, current, power, frequency and the like. Stability, interference inspection system and the like.
Second, a basic circuit debugging techniques, for example, the signal injection method of investigation without the op amp output, first oscilloscope to measure the presence or absence of the signal input source signal. If we do not use the first waveform generator, the addition of a signal fed into the input, to measure the presence or absence of an output signal of the rear end, to find the point of failure. The simplest is to clamp the touch input is shorted to ground, look at the output of op amp has no response. Of course this is only used in other audio or video amplifying circuit common. A high voltage circuit can not use this method, not to be electrocuted. Step by step investigation, in order to quickly find the problem.
2, comparative law like this, as the replacement method commonly used in the maintenance of computer truth. Such as during the same device, when applied to a different location, or elsewhere, the circuit is not working properly. So how can we judge it? First, rule out the power supply voltage problem, after comparing the input and output waveform difference, find the operating point voltage are the same. Contrast exclude problems that may arise, or replace the device with a magnifying glass to see whether the pin Weld, it was repeatedly confirmed, to be the fastest to find the problem.
3, issue zero this formulation for debugging complex integrated system, it must not be "stop-gap" thing. "Zero" meaning, refers to the event of failure or problem, will, have a check from zero from the first step to the last step until the problem is fully resolved. Required to achieve accurate positioning, a clear mechanism, reproduce the problem, effective measures, by analogy.
Third, the debugging process to seek help of theoretical knowledge engineering practice described is the law of the CCP, but the fault phenomena in engineering practice are the most concrete and specific implementation process of the project has a relationship. Therefore, when confronted with a problem, based on their experience and knowledge, then troubleshooting The method suggested above, after experiencing problems, you can go to ask help from others. But try to describe your problem clearly, measures and results, and analyze what you are about to take the other side. The other was likely to shrink by your description of the scope of the investigation as far as possible, identify specific ways, and understand your level of knowledge and skills through your description and analysis of mistake you can make, the principle may be understood and can be used in specific operations understanding to be able to give specific advice.
Many ask me above the students, mostly using a few words describe the phenomenon of error, ask questions that may arise or solution. Indeed, it did make me feel embarrassed:
1, I faced questioning tens of thousands of team members in the limited spare time, it is impossible for one-way communication is completed through continuous guidance;
2, a few words describing the information given is very limited, unable to confirm your skills, cognition, overall system solutions, making debugging environment, the recommendations can therefore given in general terms but deviation;
3, problems in practice still needs to be resolved through practice, each of the above methods are practical need for debugging programs according to the actual situation. I can not provide effective guidance through remote speculation.
Therefore, only the students to ask questions related to the future of design debugging, try to use more languages, the detailed description of the problem you encountered, by leaving an image in the public numbers, the video shows the specific circumstances of your system, a wealth of information that I was able to understand yourself and the problems encountered. Otherwise, please after you read this tweet, in accordance with the above-mentioned some specific way I excerpt, debug it on their own today.
The actual operation follows in the public number "hardware Hundred Thousand Whys" excerpts from some of the hardware production process often guilty of "stupid" and see that you have committed?
1, polarity devices, PCB pins will engage in counter.
- Power line, the bottom line is connected to forget, or reversed.
3. The connector line drawn backwards sequence
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RX, TX drawn backwards
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Transistor TO-92 package, in the end how BCE arranged it? When the welding awkward.
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When painting granted chose a package, the results simply can not buy.
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Direct copy circuit, which devices are discontinued in 15 years
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Selecting capacitors, resistors and the resistance capacity considering only, without considering the withstand voltage and power
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Are capacitance, inductance, resistance, actually there is said high and low frequency, so the results only.
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Unfinished board, do not look DRC report, only the eyes but the existence of the fly line. Results After the plate on the PCB blows the fly line.
- Thermal pad also the solder resist layer, no treatment
Extending the discussion I remember during my college summer courses in electronic design practical courses, curricular eight digital circuit is completed in accordance with the experimental test instructions on a breadboard. Usually she was more interested in electronics, the second week early to complete all the experiments, and the remaining six weeks nothing can be done.
Responsible course teacher said to me: While your experiment done, but can not give you results, basically you do not learn anything in this course. Do the students in the class two weeks basically no progress, you are responsible when his assistant. In his complete course of the experiment, the mistake is your mistake, damage to components you lose, his score is your final score.
Since then, I understand the principle, had committed an error in engineering practice is the acquisition of skills. This is the only way to advance technological capabilities. Like learning sports, dance, music, language and literature, requires a lot of training, engineering disciplines also have this capability requires the acquisition of skills by the time and frustration completed.
Here is the hardware design of the network on the ability to classify a number of statements, and now you have reached a few levels?
First level: 1, main effort spent learning tool schematics, PCB tool;
2, focuses on PCB does not go through the line go, the more intense line even afraid of the wrong;
3, for the principle of the circuit, there is no time and energy to focus on the general circuit-based to copy others, prefer books case circuit;
4, PCB, can focus on communication lines, for signal integrity, there is no clear idea of the length of the trace width. Control circuit can be designed low.
Second stage: 1, the schematic, PCB tool has capability, proficiency;
2, began to focus on circuit theory, indicators of the device affect circuit operation;
3, distribution of energy research Datasheet
4, pay attention to the difference between different types of discrete devices, capable of independent thinking when the device selection, not what circuit can copy, on what circuit.
Third grade: 1, the circuit can control risk, some of which may affect the function of the problem, when the schematic and component selection will be taken into account. Not in the circuit board back to the debugger, and before going to solve the problem.
2, circuit design, consider the design tolerances, considered undesirable components of, for example, change with temperature, it affects the accuracy of the voltage impact indicators.
3, PCB design, consider the communication line, but also consider the high-speed, radio frequency, high current impact on circuit performance. Able to analyze the signal timing, impedance continuity.
4, signal integrity problems will be resolved by means of analysis or simulation tools.
Fourth grade: 1, other than to consider the dimensions of functionality: low cost, ease of processing, the device is easy to buy, easy to test, easy to diagnose problems online, transport or vibration difficult to damage, easy to maintain, easy to maintain.
2, the circuit design can meet the needs of high reliability.
3, can innovation, it is possible on existing circuits or programs to make innovative design; or advanced technology can be realized in a technical field, of a prior art system to make the breaking point. Be able to apply practical value of the patent, the effective protection of innovation of their products.
4, can be designed to support a massive shipment of products.
For views between knowledge, ability and experience, you can be a tendency to look at from below a multiple-choice questions.
Unfortunately, if you got some serious incurable diseases, see the following three doctor's resume, which would you choose a doctor?
