Analysis of Chaos Signal Generator for Question D of 2022 Electric Competition
Table of contents
foreword
This blog was almost finished when the competition was over, but it has been delayed until now due to some personal reasons. When I returned to school, I suddenly remembered that I had an unfinished blog. I will finish writing it today. commemorate!
As of now, the 2022 e-sports competition has also ended, so let’s not talk about the polite words. Tiredness must be tiring. This time our team’s results are not very satisfactory. There is no way, let’s accept our fate, and look forward to competing in the national competition next year. Go straight to the point.
Because the direction of our laboratory is instrumentation and signal, when the topic came out, our group has been very entangled, whether to choose D or F, it seems that only these two topics can be done.
When I looked at Question D at a glance, I couldn't understand it at all. After all, I had never heard any chaotic signals before. I searched the Internet for what cryptography was involved. Our first reaction was that it was very difficult. In the past, I only heard about the security of passwords from the students who were majoring in computer science. At first, my first reaction was whether to make some software on the microcontroller. After all, I don’t know much about this aspect. Now think about it. Really whimsical.
Let’s talk about question F again. At the beginning, I feel that I can understand it a little bit. I probably have a framework in my brain. The team members discussed it later, and the reaction later was that it was over. We only started to learn these knowledge points in the third year of school. We only know a little bit of superficiality now. Barbie has Q, and this year I fell. At that time, I joked that I was going to sleep for four days and three nights. .
1. Topic analysis
Since everyone sees our topic and knows what topic we chose in the end, I will stop talking nonsense and just look at the topic directly.
I have been analyzing from the beginning of the game to writing this blog now. I have summarized a few difficulties. Everyone is welcome to add:
1. Chaotic circuit selection:
After the title, it introduces us to three circuits. However, the Copitts circuit is implemented with a triode. This topic restricts the use of op amps, so this circuit can be passed. Looking at the Vanderpoor circuit, most of the searches on the Internet require external excitation, and this topic is also limited. , this is also pass. So you can only choose Chua's circuit later.
2. Framework. There is nothing to say about this, it is the overall framework and which modules the circuit is divided into. When we started to make this circuit, we slowly discovered that the circuit is actually divided into Chua's circuit module , gyrator module , shift module and follower amplifier module . There may be an extra module in the bandwidth, but we haven't made it here, welcome to add.
3. Single power supply. This is the main difficulty. Anyone who has done this topic knows that the waveform will be cut when using a single power supply for simulation. On the first day of the competition, I searched information with our team members and simulated with Multisim for a whole day. Chua’s circuit was solved, but the active inductor could not be simulated at all. If we use dual power supplies, it will be fine.
Let me show you the Chua's circuit with a single power supply. That's right, it is to add a power supply of 1/2 VCC to the original ground. This can be realized with a resistor divider, and it can be realized with a single power supply. If you are interested, you can try it. .
4. Bandwidth. This is very difficult. I can only say that this is the most difficult question D, and we didn't make it. If the basic 17mH inductance circuit is used, our team members calculate that it is only more than 20 KHZ. We have some theoretical support here, and you can try it. Our team was already " squeezing " the bandwidth very, very much. In the end, we could only theoretically reach more than 600 KHZ, which was still far from enough. just look at the picture.
These are the approximate calculation formulas. These are all found by my team members. I still want to brag about them here. Our team consists of me, a boy, and their two girls. Most of the Internet said that girls should not be selected as team members for this kind of competition, but they have a good impression on my side. My side focuses on hardware, so the software and reports are handed over to them. I have almost no experience in those aspects. What did you worry about. Girls, be careful, all these materials are found by them, and the gyrator in our group is also imitated by them. I am only responsible for drawing PCB, soldering and testing, so I still hope that you don’t bring them with you. Colored glasses to select players.
2. Design process
1. Chua's circuit
In fact, this is the most typical Chua’s diode. If you don’t do the bandwidth one, this is a dead circuit. Just take a rail-to-rail chip and follow this diagram, but if you want to do high bandwidth, chip selection is very important. , and the latter resistance value may need to be increased or decreased proportionally.
It is recommended to put C1 and the Chua's circuit on the same board, because we generally change the waveform by changing the R in the above picture, so your C1 can only be placed on the Chua's module or the shift module, and it is recommended to put the Chua's module here.
Supplement: After all, we don’t know very well here. We also saw other awesome Chua’s circuits on the Internet, but because of limited time, we can only do the most basic ones. Welcome to add other better Chua’s circuits.
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Let’s talk about the bandwidth separately here. If you follow the calculation formula, 40MHZ is easy, but this bandwidth is very, very dependent on the chip. We simulate the same circuit above and change the chip, and the result is completely different. Our side does not move Chua’s circuit, only modulating the inductance, capacitance and resistance in front , the simulation can only be reduced by hundreds of times at the same ratio, which means that it can only reach a few M~tens of M at most, and it can’t reach 40M, or that In a word, it is particularly dependent on the chip, and interested partners can try to simulate it by themselves. However, we saw an article on the Internet that introduced other methods of widening the frequency band, that is, Chua's resistors are also scaled or increased, but that method is more troublesome and time is limited, so this method was not adopted.
Then some partners will ask me, you said that it can reach several M~tens of M in simulation, so why do you say that it can be "squeezed" to more than 600 KHZ at most?
Because the theory is just a theory, we scaled down all except Cai’s by 20 times, and then modulated it into a double-rotation wave. After measuring the actual resistance and calculating it, it was only more than 600 KHZ. We have scaled the actual object by 1000 times, but the graph only has a single cycle, and all other waveforms are absent. If there is, then our theoretical value has reached 40M. But no, in the end, I could only try one by one, and finally tried 20 times.
Later we found that when some multiples of only a single cycle are available, you can follow it with a follow-up zoom , and the result can produce other waveforms required by the topic, but the three-cycle instability , this needs to be paid attention to. In addition to this method, how much frequency can be "squeezed" out. Interested partners can try it, but we have not tried it. Anyway, it can be higher than the original frequency, but the higher the frequency, the smaller the peak-to-peak value behind it. The required magnification needs to be larger.
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2. Rotator
You can refer to it and search for this circuit on the Internet. We made the circuit according to this template, and the specific parameters should have formulas, so I won’t explain too much here. The gyrator was simulated by my team members looking for information, so I may not introduce too much in this regard, but it is basically this circuit template, and then the whole circuit is equivalent to an inductor to achieve the third point of the topic without inductance. .
3. Shifting circuit and following amplifier
(1) Shift circuit
The topic requires five waveforms, so we need to change the value in one place to change the waveform of the chaotic signal, or this picture
The most convenient way is to change the resistor R. In fact, it is to make the resistor R a separate module, and then add some controllers, such as relays or manual switches. Check out the topic requirements here
The topic says that programming or switches can be used, so we generally have two options, one is a single-chip microcomputer control relay, and the other is a manual switch. Most people in our laboratory chose relays, but our group chose the manual switch at the end. Maybe we think this kind of switch is convenient to use, and if a relay is used, it needs to be controlled by a single-chip microcomputer, which is quite troublesome. , and finally chose this economical (mainly lazy, this method is simple and rude) method. here is the image
Originally, I wanted to use a four-speed switch, but the laboratory did not have suitable components, so I used a single-pole double-throw switch in series.
(2) follow zoom
Because of the requirements of the title, it is necessary to output 80% VCC during single-rotation and double-rotation, so here we need a follower + amplifier, just two op amps, so the fourth point can also be satisfied. This basic circuit will not be published. It is worth noting that a single-pole double-throw switch is required behind the shift module just mentioned. Choose whether to zoom in or not, because if you zoom in on those without required amplitude in a single week, these graphs may be distorted.
Summarize
This exciting electronic competition is over. I just want to say that it is a pity for this year's topic. Our team prepared a lot of self-made modules before the competition, but basically they are not used. I can only say that this year's topic is different from the previous ones. The topic is completely different, and I can only say that my strength is not enough and I still have to practice.
But if you just talk about this topic, except for the bandwidth, there is basically no difficulty. Chua's circuit and gyrator are circuit templates. If you understand the calculation formula, you can basically use it directly. But after participating in the laboratory, I still learned a lot of knowledge that is not available in books. After understanding the theory, it is only a theory. If you want to make a physical map, there is still a big difference. Finally, let’s post some pictures of our results!
Note: It is a bit unstable on the three-cycle side, and the waveform will jump a little bit. As for why it has not been figured out yet, I hope some big guys can give us some advice.
Attach the schematic diagram of the whole circuit: (5 messages) 2022 Electric Competition D Problem Chaotic Signal Generator-MCU Documentation Resources-CSDN Library