Chapter 487 Core Components of Photoelectric Encoders
Gao Zhendong's words were originally intended to explain why they made incremental encoders first, but when the Guangyang Factory heard this, although they didn't understand what an incremental encoder was, their first reaction was to feel a little embarrassed.

It might be that our skills are not good enough. In order for us to keep up, Chief Engineer Gao had to teach us the simple things.

"Mr. Gao, can you explain the increment and multiple laps you mentioned?"

I can guess that it can rotate many times.

However, if the increment is not explained, they may not understand it. If such technical terms are not clarified, random guesses may sometimes go in the wrong direction or even in the opposite direction.

For example, "holotype fossil replica". The "homotype" in holotype has nothing to do with the direction, but in connection with the "model" and "replica" behind it, many people will guess wrong based on their intuition.

But what this thing really means is "a copy of a holotype", not "a copy of a fossil of a holotype". Moreover, holotype is a special term. For ordinary people, it can be loosely understood as a standard fossil of a species, and has nothing to do with direction, holotype or anything like that.

Gao Zhendong briefly explained what an incremental encoder is and what an absolute encoder is.

"I understand. The increment can only measure the change in rotation, but it cannot directly output the specific angle of rotation." said a technician from the Guangyang factory.

Gao Zhendong shook his head: "Not entirely correct. The external manifestation of the core difference between them is what you said, but the real core is not like this. It needs to be deeper."

Seeing that everyone was a little confused, he continued: "The real core is that the output of the incremental encoder is only the output increment. The output data does not correspond to the position of the encoder shaft, which means that the relationship between the current position and the initial position cannot be directly determined."

The comrades at Guangyang Factory were aware of the problem: "How can we solve it in practical applications?"

"Technically, a counting circuit can be added externally to make a judgment. However, if part of the incremental output signal is lost due to interference, power-off signal line failure, active shutdown, etc., then the accumulated value of the rotation angle is wrong. It is necessary to weaken or recalibrate it through other technical means or management means. For example, it needs to be reset to zero after active shutdown, but this still cannot completely eliminate its disadvantages."

Gao Zhendong explained it in quite some detail, after all, it was the first time for the comrades at Guangyang Factory to come into contact with this thing.

"Ah, I see. An absolute encoder outputs data that corresponds one-to-one to the position of the shaft. You can directly read the output data to know how many degrees it has rotated."

"Yes, whether it is single-turn or multi-turn, the output of the absolute encoder corresponds to the angle of rotation of the shaft. At the same time, the output of the absolute encoder is basically digital output, which is very convenient for future computer-based control systems."

The reason why it is called "basic" is that some absolute encoders also have analog outputs for compatibility reasons, such as 4~20mA, 0~5V analog outputs.

However, under normal circumstances, this analog interface is generally not used, as it increases system complexity and introduces errors.

After hearing this, Mr. Yang had an idea: "Chief Engineer Gao, since relative encoders have so many defects, why don't we just make absolute encoders directly?"

Gao Zhendong laughed. This is a mistake that many people often make when they first come into contact with encoders, thinking that incremental encoders and absolute encoders are binary opposites.

Increments have their uses, and absolutes have their absolute circumstances.

He shook his head and said, "Mr. Yang, there is actually no difference between incremental encoders and absolute encoders. The main reason is that the application scenarios are different and it is difficult for them to completely replace each other. However, in theory, the two can be converted into each other through certain technical means. I suggest that you start with incremental encoders because most of the current control systems are based on analog means and there are not so many digital control environments to support absolute encoders. In this regard, incremental encoders are better."

After saying that, he explained the reasons in detail to Mr. Yang.

Although the incremental encoder also outputs digital pulses, it is much simpler to introduce digital pulses into an analog control system than to introduce a series of digital conversions into an analog control system.

Moreover, the advantage of absolute encoder is that it is an absolute quantity, and participating in calculation and comparison is its core advantage. However, this core advantage is not fully utilized in analog control systems.

After listening to this, Mr. Yang nodded repeatedly: "Mr. Gao is really thoughtful. When we develop new things, we should not only consider the technology itself, but also whether the application environment can match it. I have learned a lot."

Gao Zhendong nodded and gave another reason for not working on absolute encoders for the time being: "Besides, the technology of absolute encoders is more complicated. You guys should work on incremental encoders first. Once you have experience, we can consider absolute encoders."

I have the skills, but you may not be able to accept it all at once, so let's proceed step by step.

The comrades at Guangyang Factory were a little bit amused and confused. It turned out that it was because we were too inexperienced and too naive.

A comrade from Guangyang Factory had a flash of inspiration: "Chief Engineer Gao, if we must use an absolute encoder due to necessity, can we use a digital circuit to count the output of the incremental encoder and then output the digital quantity? At the same time, use batteries or other means to ensure that the digital quantity is retained when power is off?"

Wow, this young comrade is pretty good and has a lot of ideas.

"Haha, your idea is good. Although this cannot completely solve the problem, it can meet the requirements to a certain extent. This is why I said that the two can be converted into each other in theory. Your factory is engaged in analog devices, but it seems that you have also done some research on digital circuits."

This comrade does not look like a recent graduate, so it is unlikely that he has systematically studied digital circuits in school.

"Hey, last year I saw a book called "Logical Operations and Digital Circuit Design" in a bookstore. I thought it was very interesting and it was the direction of future development, so I bought it and studied it by myself."

Gao Zhendong smiled and nodded. Well, the young man is still very studious! At this point, the comrade from Guangyang Factory suddenly remembered something.

"Oh, I remember now, Chief Engineer Gao, the author of that book is you, right?"

The other comrades looked at Gao Zhendong with awe. They only knew that he was a technical expert who was highly respected in the department, but they could not feel how advanced his skills were, except for the content related to the encoder.

All of a sudden, I had a deep feeling that it was incredible that a book could be published directly on digital circuit logic operations, which sounded like high-tech content.

Only General Yang looked at this comrade with an expression that said, "Good job, kid. You'll have a bright future ahead of you."

He cleared his throat and said, "Boss Gao, Xiao Xu is a young technical backbone of our factory. He is always diligent and eager to learn, and has many ideas."

Although this "young backbone" is actually older than Gao Zhendong, it did not affect him at all in introducing him to Gao Zhendong under the name of "Xiao Xu".

Gao Zhendong was still in a good mood. As long as a mentally normal person hears others recognize his real achievements, he will not feel unhappy.

"Well, Comrade Xu is good. You can work harder in this area. The design and application of photoelectric encoders are more digital. It will be beneficial for this job if you know more about digital circuits." Gao Zhendong encouraged.

Mr. Yang nodded: "Well, in our work, we will pay attention to giving full play to the strengths of our comrades and tapping their potential."

The other people at Guangyang Factory looked at Xiao Xu with envy, but not jealousy.

This is what he deserves. He is the only one in the whole team who can talk about this book and come up with the idea of ​​using low-bit incremental encoders to replace absolute encoders. This is ability and talent.

If you are not good at it, just practice more. Being jealous of others will not help improve your own situation. Everyone still has a good heart.

Seeing that everyone had their own understanding and ideas about the incremental encoder, Gao Zhendong took out a pen and paper and drew a picture.

"Comrades, this is the core of the photoelectric encoder, the photoelectric encoder disk."

Everyone came forward to take a closer look. Is the progress so fast? Are they going to teach us all the core stuff?
The picture shows a disc with three circles of long holes from the outside to the inside.

The outermost circle is evenly distributed along the circumference.

Going inward, it looks like the number of holes is the same as the outer circle, but in detail, they are not radially aligned with the outer circle, but are offset by a small angle.

The innermost circle is quite special, with only one hole.

It looks very simple and the processing is not complicated.

Looking at this "core component", Yang finally understood why Gao Zhendong asked them to make the incremental photoelectric encoder first. This thing looks really simple.

For them, the difficulty lies in figuring out the principles and the appropriate structure, but when it comes to processing, it is actually not that difficult.

Looking at this disc, everyone was discussing what it meant and how to achieve incremental output.

"This should be caused by the encoder disk rotating, which causes the light to turn on and off, and then pass through the photosensitive element, and naturally output a pulse signal."

“It looks simple, but it’s a great idea.”

"I don't think it's that simple, otherwise there wouldn't be three laps."

Comrade Xiao Xu looked at this and thought for a while, then blurted out: "I know the purpose of the second circle!"

Everyone looked at him, including Gao Zhendong, to see if his idea was correct.

"The pulse output of the second circle has a phase difference with the first circle. By detecting the phase difference between the two, we can determine the direction of rotation."

After hearing what he said, everyone looked at Gao Zhendong, wanting to know if he was right.

Gao Zhendong smiled and nodded: "Yes, you are right, not bad, not bad, very sharp, and the basic skills are very solid."

(End of this chapter)