Curriculum design task book
Course Name: Electronic Technology Course Design
Title: quiz responder
Specialized courses:
Student name:
Student number:
Instructor:
Approval:
Task date: Monday, February 28th, 2009, 65438.
Design completion date: 2065438+0065438+1Friday, October 8th.
Design content and design requirements
First, the design content:
1. Design an intelligent answering device that can accommodate 8 teams. Each team has one answering button, and the number of buttons corresponds to the number of players.
2. The transponder has the functions of first signal recognition and data latching. After the host resets (clears) the equipment, answer the command first. When the first group of players touch the button, the indicator lights up. After that, the touch keys of other groups are invalid.
3. Design a circuit to display the first group 1~8 groups with a digital tube.
4. The responder has the function of answering for 30 seconds regularly. When the host gives the order to answer first, it starts to count down and shows the time on the display. When it is time to answer first, the buzzer will send out an alarm signal, and the input circuit will be blocked, and the player is forbidden to answer first.
5. Design the foul judgment circuit and display it with indicator light.
6. Set the scoring display circuit. Each group preset 100, the correct answer 10, and the wrong answer 10.
7. Function expansion (optional)
Second, the design requirements:
1. The idea is clear, and the overall design block diagram and circuit diagram are given;
2. The unit circuit design, giving the specific design ideas and circuits;
3. Write a design report;
Main design conditions
1. Debugging in the "Comprehensive Laboratory" and "Electronic Laboratory" on the fourth floor of the south building of the laboratory building.
2. Provide components and chips needed for debugging the experimental box and circuit.
instruction format
1. Course design cover;
2. Task book;
3. Instruction catalogue;
4. Design general idea, basic principle and block diagram (general circuit diagram);
5. Unit circuit design (circuit diagram of each unit);
6. Installation and debugging steps;
7. Fault analysis and circuit improvement;
8. Summary and experience;
9. Appendix (parts list);
10. References;
1 1. Course design score sheet
catalogue
1 introduction 6
2 design scheme 7
2. 1 design scheme and requirements 7
2.2 Design ideas and principles 8
2.3 Design of Unit Circuit 8
Circuit design of (1) transponder 8
(2) Sequential Circuit Design 9
(3) Alarm circuit design 1 1
(4) Scoring circuit design 1 1
2.4 overall design 12
3 EWB simulation 15
4 Fault Analysis and Circuit Improvement 15
Pin Diagram and Menu of Five Important Original Parts 18
6 Experience 20
7 Appendix 22
Reference 22
1 Introduction
Quiz is a lively way of education, and rushing to answer questions is a very common way of answering questions in quiz. Answering first can arouse the great interest of the contestants and the audience, and make people quickly increase some scientific knowledge and common sense of life in a short time. But in this kind of competition, it is easy to misjudge who answers first, when to answer first, how to calculate the answer time and so on. If you only rely on the subjective judgment of the host. Therefore, we need an intelligent responder with automatic locking, setting and clearing functions to solve these problems.
In this course design, we will mainly design an eight-person timed answering device. The main functions he wants to realize are as follows: (1) Provide each of the eight contestants with an answer button numbered S0, S 1, S2, S3, S4, S5, S6 and S7; (2) The host can control the system to clear before answering; (3) The transponder shall have the functions of data latching and display. After the start of the game, if a player presses the game button, it is necessary to display his number until the system is cleared by the host and prompted by the speaker. It is invalid for others to press the corresponding button again. (4) The answering machine should have automatic timing function, and the time for answering at one time should be set by the host at will. When the host starts the "Start" key, the timer automatically counts down and displays it on the display screen. At the same time, the speaker makes a short sound; (5) Only when the contestants compete for answers within the set time can they compete effectively. If the answer is valid, the timer stops working and displays the start time of the answer until the system is cleared; (6) If no player answers first within the set time (press the corresponding button), the system will give an alarm for a short time, and the player is prohibited from answering first after the set time. The timer shows 00. The digital transponder consists of a main circuit and an expansion circuit. The priority coding circuit, the latch and the decoding circuit output the input signals of each group on the display; The control circuit and the host switch are used to start the alarm circuit to form the main circuit. The signal generated by the second pulse is output to the display through the timing circuit and the decoding circuit to realize the timing function and form an expansion circuit.
The timed answering device made of this designed circuit can easily control the answering contest between 8 people or 8 teams, making this activity more interesting and fair.
2 design scheme
2. 1 design scheme and requirements
1. The main devices given are: 74LS14874LS13874LS192555 LED display screen.
Functional requirements: design a quiz ball, which can be played by 8 people at the same time and has the function of answering questions regularly. Specific functional requirements are as follows:
Basic functions:
(1) Design a quiz responder, which can be used by 8 players or 8 teams at the same time. Their numbers are s0, s 1, s2, s3, s4, s5, s6 and s7.
(2) Set a control switch for the program host to reset the control system (turn off the lights of the digital tube) and start the responder.
(3) The transponder has the functions of data latching and displaying. After the game starts, if a player presses the game button, the number will be locked immediately, the player's number will be displayed on the led digital tube, and the speaker will give a sound prompt. In addition, it is necessary to block the input circuit and prohibit other players from rushing to answer. The number of priority contestants is kept until the host clearing system.
(4) The responder has the function of answering for 30S at a fixed time. When the host gives the order to answer first, it starts to count down and shows the time on the display. When it is time to answer first, the buzzer will send out an alarm signal, and the input circuit will be blocked, and the player is forbidden to answer first.
(5) Design the foul judgment circuit and display it with indicator light.
(6) Set the scoring display circuit. Each group preset 100, the correct answer 10, and the wrong answer 10.
(7) Function expansion (optional)
2.2 Design ideas and principles
Composition framework of multi-channel intelligent responder
The designed responder circuit mainly consists of responder circuit, trigger circuit, trigger latch circuit and seven-segment display decoder.
Working principle: After the power supply is turned on, the host computer switches the switch to the "reset" state, the responder is in the prohibited state, the digital display goes out, and the timer displays the set time: the host computer switches the switch to the "start" state and announces that the responder works. The timer counts down and the speaker gives a sound prompt. When the time is up, but no player answers first, the system will call the police, block the input circuit, and prohibit the player from answering first. When players compete for answers within a fixed time, the responder completes: priority judgment, number locking, number display and speaker prompt. After a round of rushing to answer, the timer stops, the second rushing to answer is prohibited, and the timer displays the remaining time. If you answer first, the host must operate the "Clear" and "Start: Status" switches again.
2.3 unit circuit design
Design of (1) transponder circuit
This part mainly completes two functions: one is to distinguish the order of the player's keys, latch the number of the priority responder, and decode the number displayed by the display circuit; Second, other players are forbidden to press keys. The priority encoder 74ls 148 and RS latch can complete the above functions, and the circuit diagram is shown below. The working principle of this circuit is as follows: When the host computer controls the switch S to reset.
Finally, the R non-terminals of the RS flip-flop are all 0, and the outputs of the four flip-flops (Q4-Q 1) are all set to 0, so that the BI of 74ls 148 is not equal to 0, and the display lamp is turned off: the gate input ST of 74ls 148 is not equal to 0, which makes it in a working state, and the latch circuit does not work at this time. When the switch S is turned on by the host, the priority encoder and the latch circuit are in working state at the same time, that is, the transponder is in waiting working state, waiting for the signal from the input end. When the player presses the key (such as s5), the output of 74ls 148 is not = 0 1Y0, nor is the output of YEX =0 10. In addition, CRT= 1 makes the NOT of ST of 74ls 148 high, blocking the input of other keys. If you rush to answer again, the host needs to "clear" the S switch again and reset the circuit.
(2) Design of timing circuit
The host can set the time of an answer according to the difficulty of answering the question, and pass
The timer circuit presets a counter, and the clock pulse of the counter is provided by the second pulse circuit. A circuit with preset time can be designed by using two decimal synchronous addition and subtraction counters 74Ls 192, decoder 7448 and short-lived digital tube. Among them, two blocks 74LS 192 realize subtraction counting, which is displayed on the digital tube through the decoding circuit 74LS48, and its clock signal is provided by the clock generation circuit. 74 192 preset number control terminal realizes the preset number, the program host sets the answer time according to the difficulty of answering questions, and the counter is preset through the preset time circuit, and the clock pulse of the counter is provided by the second pulse circuit. After the button pops up, the counter starts to count down and displays the time on the seven-segment digital tube with common cathode. When someone answers first, it stops counting and shows the countdown time. If no one answers first, the countdown time is up, and the low level is output to the timing control circuit to control the alarm circuit to alarm. At the same time, the player's first answer is invalid in the future.
74LS 192 is a synchronous decimal reversible counter with dual clock inputs and functions of clearing and setting. Its pin diagram is as shown in the figure:
(3) Design of alarm circuit
In this part of the circuit, we are a multivibrator composed of 555, the oscillation frequency fo= 1.43/(R 1+2R)C, and its output signal drives the speaker through a transistor. PR is the control signal, when PR works as a harmonic oscillator; When PR is low, the circuit stops vibrating.
2.4 overall circuit design and circuit diagram
After the above analysis, we connect all the circuits and control them properly, and get the overall circuit diagram of the eight-bit timing responder. As shown in figure 1 1:
Its working principle is:
The numbers of the eight players are 0, 1, 2, 3, 4, 5, 6, 7, and the corresponding buttons are S0, S 1, S2,
S3、S4、S5、S6、S7；
First of all, the host sets the answer time according to the difficulty of the topic. This setting can be realized by adjusting the levels of the four pins D, C, B and A of the input two pieces of 74LS 192 (for example, to set the time to 60s, set the D, C, B and A of 10/92 to 0, 1 65432 respectively. When the host reads the topic and says "Start" and puts the switch in the "Start" position, the output is high, which is divided into three ways: one way is output to the input end of the integrated monostable flip-flop 74LS 12 1, which makes it generate a single pulse with a period of 0.5S to drive the alarm circuit to sound, that is, to realize the function of sounding prompt; The other path is output to the LD terminal of 74LS 192, which makes it at a high level and starts the countdown; There is also an output to the C terminal of the latch;
If there is no player's Anton key, the output of 74LS373 is all high level, and 74LS 148 also outputs high level, and the E0 terminal outputs low level to the 7448 turn-off input RI/RBO terminal, so that the signal will not be displayed on the display screen through 7448;
When any transponder (1) presses the button, the eight-D latch 74LS373 works, and the output terminal corresponding to the input terminal (1) outputs a high level, so A0 ~ A2 of the eight-bit level output by the latch is encoded into a three-bit binary code corresponding to the input signal by the 8 ~ 3 eight-bit priority encoder 74LS 148. However, the output level of pin 15(E0) of 74LS 148 changes from low to high, and the binary code output to the seven-segment decoding display 74LS48 is decoded and output to the seven-segment common cathode digital tube, so the corresponding number (1) is displayed on the display. At this time, the RI/RBO terminal of 7448 outputs a high level, and the switch also outputs a high level. Both of them output low level through NAND gate, and then output to C terminal of latch 373 through AND gate or low level, which plays the role of storage. If other players press the corresponding button again, there is no corresponding output, that is, the function of rushing to answer is realized;
At the same time, the E0 segment of 74LS 148 outputs a high level to the input terminal of the integrated monostable flip-flop 74LS 12 1, so that it generates a single pulse with a period of 0.5S, which drives the alarm circuit to sound, that is, the function of sounding prompt is realized;
At the same time, the output level of GS terminal of 74LS 148 changes from high to low, and it is 0 after the second pulse is generated by the second pulse generator, so that no pulse reaches the Down terminal of counter 192. The counter stops working and keeps the original display unchanged, that is, it realizes the function of stopping the countdown and recording the answering time first;
When the player answers a question, the host puts the switch in the "reset" position, and outputs a low level, which is also divided into three ways: one way is connected with E0 terminal (high) of 74 148, and the other way goes high and outputs it to enable terminal C of 373, so that the latch no longer latches data. At this time, the display of the first answer part is closed, and the reset is realized without display;
The other low level is output to the LD terminal of counter 192, and the CR terminal is also low level, so the corresponding display outputs preset data;
When the timer counts down to 00, if no player presses the button, the two borrow outputs of 74LS 192 both output high levels, and then the two output high levels to the B port of monostable trigger 74 12 1, thus generating a pulse stimulation alarm circuit with a period of 0.5s, and giving a sound prompt.
Scoring circuit diagram
3 EWB simulation
According to the overall circuit diagram, select a chip on the simulation software EWB and connect it, then start the switch to observe.
When the simulation result is consistent with the expectation, it proves that the simulation is successful. The designed circuit is correct.
Fault analysis and circuit improvement
1. Numbers are not displayed on the display. We test from the background to the front desk. First of all, we add a voltage of 1.5 ~ 2V to each pen segment, and see whether the corresponding pen segment is bright or not to judge whether it is intact. If it is intact, continue to test whether the 74ls 148 chip is intact. A set of binary numbers (represented by high and low levels 1 and 0, here pay attention to the power supply voltage above 8V) are randomly input at the four input terminals A, B, C and D of 74ls 148 to see if the numbers can be displayed. The common problem of no display failure lies in these two links.
2. If the numbers displayed on the display do not meet the requirements, under the premise of correct design principles, firstly, whether the outputs A-G of 74ls 148 are connected with the pen segments A-G of LED tubes is judged by testing. The method is to input the high and low levels of output A ~ G of 74ls 148 respectively according to the rules, and observe whether the LED tube displays the corresponding numbers. If this link is normal, the problem lies in the diode coding circuit, and then check one by one.
3. If it can't be latched, or 1 and 7 can't be latched, the problem lies in the latch circuit, which should be analyzed in principle. The design principle of the latch circuit is that the latch function terminal le of CD45 1 1 is enabled and the high level is effective, that is, the latch function is executed when the high level is input. The latch should be able to lock the first scrambled signal and reject the interference of the subsequent scrambled signal. How to design? We analyze the display segments of ten numbers from 0 to 9. Only the D segment of the number 0 is on, and the G segment is off. Other numbers are at least a little invalid. Therefore, 0 can be distinguished from other numbers. We feed back the input signals of the A-pen segment and the G-pen segment of the LED lamp to the latch circuit, and control the input of the latch terminal LE to be 0 or 1 (whether it is latched or not) through the latch circuit. When LED shows 0, LE=0, and the decoding chip of CD45 1 1 is not latched; When the LED display shows other numbers, LE= 1, and the chip is latched. So as long as the display shows 74ls 148, the decoding chip will not be locked, and other displayed numbers will be latched. Therefore, as long as a player presses the button, the number 1 ~ 8 must be displayed on the display screen, and LE= 1 chip is latched. After that, any other player presses this button again, and it won't work. For example, press the SB 1 key first, and the display will show that the chip with 1 and LE= 1 will be latched. If other players press SB2~SB8 again, 1 will still be displayed on the display screen, and any key signal after SB 1 is pressed will not be displayed. Until the host presses the clear key SB9, the display screen shows 0 again, LE=0, the latching function is released, and a new round of scrambling begins.
If all the numbers can't be latched, it means that no matter what numbers are displayed by the LED, the five-pin input of 74ls 148 is level, which may be that the five-pin is short-circuited with the ground or the two diodes VD 13 and VD 14 of the latch circuit are disconnected. If only 1 and 7 bits are not displayed, we can analyze the reasons: when 1 and 7 bits are displayed, the G segment is not lit, the G output terminal of 74ls 148 is low, VD 14 is turned off, and the D segment of B segment is not lit, so the transistor VT1.
4. In the test process, we must pay attention to the selection of high and low level test voltage values according to different circuits. For example, for LED lamps, the high level only needs 1.5 ~ 2V, while the input of CD45 1 1 needs more than 8V to reach the high level. If you choose high, you will burn the pipe; If you choose low, you will not see the effect and even make a wrong judgment.
5. To judge PNP transistor and MPN transistor: use multimeter R× 1k (or R× 100). Connect one pin of the transistor with a black contact pin and connect the other two pins with a red contact pin. If both resistance values indicated by the pointer are large, the black contact pin is connected to one pin of the transistor and the red contact pin is connected to the other two pins. If the two resistance values indicated by the pointer are both large, then the pin connected to the black stylus is the PNP base; If the two resistance values indicated by the pointer are very small, then the pin connected to the black stylus is the NPN base; If the resistance indicated by the stylus is large or small, then the pin connected by the black stylus is not the base. This requires another pin to try. The above method can not only judge the base, but also judge whether it is a PNP transistor or an NPN transistor.
After judging the base, we can further judge the collector and emitter. Suppose one pin is the collector and the other pin is the emitter. Then switch the assumed pins in turn, and then estimate the β value, in which the assumption that the β value is large is correct. So the collector and emitter are also judged.
Five important original pin diagrams and their function tables
( 1)74ls 148
Pin diagram
(2)74ls 192
Pin diagram
function table
(3)555
Pin diagram
6 summary and experience
In a blink of an eye, the two-week digital electronic course design ended in a blink of an eye. Through this course design, I learned a lot that I can't learn from textbooks, and at the same time strengthened my ability to do things, think and solve problems, which benefited a lot.
Through teacher Yang's lecture, teacher Yang explained the general idea of design, what function should be realized in each step and how to realize this function. And our task is to find out the information about the functions of each chip through this lecture by Mr. Yang, and realize its functions through the chip. The next task is to find information, design circuit diagram and simulation.
In order to understand the function of 74LS 192 chip, I borrowed some books from the library, looked for information on the Internet at the same time, and then looked for logic functions. After some efforts, it was finally solved, and the functions of other chips should be slowly pondered. In the process of curriculum design, I think it is to consolidate and strengthen textbook knowledge. Because there is too much knowledge in the textbook, and there is not a good use of the amount to understand the role of each component during the recess, the content of the exam is limited, so in the course design process, we have learned a lot about the role of many components and their use in the circuit.
In the past, the learning process was too superficial, but now, if we want to design the curriculum, we must have a deeper understanding of the knowledge used. Because the content of curriculum design is closer to real life than the theoretical knowledge in books, the transformation from theory to practice is often a difficult process, just like a roadblock. But we are not afraid, because we believe we can do it.
The main task of the last few days was the design and simulation of the main circuit. Although there are some problems in design, which are sometimes considered to be correct, there are also some problems in simulation. For example, in the main circuit diagram of the design, the light bulbs in both directions should be in a state. I think the circuit diagram is correct, but there is a problem after the simulation, that is, one is out of state, and everything else is correct. After repeated inspection, there is no problem. Later, I asked Mr. Yang, and there was no problem. In fact, this kind of problem will not appear in practice, so you should ask the teacher if you don't understand, which will save a lot of time.
The wiring diagram is connected, and here is the wiring, which is a troublesome thing. First of all, we should test whether there is any problem with the chip, the circuit board and the wire. This series of work is meticulous, and there is no room for carelessness. Be careful, patient and persistent when wiring, so as to get things done well. First of all, the layout of the line should be beautiful, practical and concise, and all aspects should be considered, otherwise it is just empty talk. After connecting one-step circuit at the same time, the most important thing is to check whether this part of the connection is correct.
Through this course design, I understand that it is very important to combine theory with practice. Theoretical knowledge is not enough. Only by combining theoretical knowledge with practice and drawing conclusions from theory can we really serve the society and improve our practical ability and independent thinking ability. The problems encountered in the design process can be said to be full of difficulties. After all, this is the first time to do it, and it is inevitable that you will encounter various problems. At the same time, you will find your own shortcomings in the design process, and your understanding of the knowledge you have learned before is not deep enough and your grasp is not firm enough.
This course design, I learned a lot of things that I can't learn in class, such as thinking independently to solve problems, improvising when mistakes occur, and cooperating with others to improve together, all of which benefited a lot. In the future, production should be easier, and I have the ability to complete this project with high quality.
The two-week course design has ended, and I will cherish this unforgettable time. She let me know that behind any small achievement, there may be many hardships hidden.
Here, I would like to thank Mr. Yang for his careful guidance, other teachers who act as agents for curriculum design, and also express my heartfelt thanks to them!
7 Appendix. Component list
74ls 148 1 74ls 138 1 74ls 192。 2 555 2 JK trigger 2 bread board 1 debug box 1.
Take the exam and contribute.
1. Electronic Circuit Design, Experiment and Test (2nd Edition)
Huazhong University of Science and Technology Press-edited by Xie
2. Application of new integrated circuits-course design of electronic technology foundation
Liang Editor-in-Chief Huazhong University of Science and Technology Press
3. Basic experiment of electronic technology
Higher education press-edited by Chen Daqin.
4. Design Guide of Electronic Technology Curriculum
Higher Education Press-edited by Peng Jiehua.