1th Phase 2015-7-2
The initial topic is communication class, and instrument and instrument class. Do the infrared optical communication and frequency characteristic analyzer two questions.
First, Progress:
Analog part: The transmitter side to remove the front potentiometer directly connected to the capacitor side of the coupling, the receiving end of the circuit skip the pre-amplified transistor.
Short transmission distance, about 70cm;
Digital part: MCU at 4800 baud rate transfer key value, and simple character to double-machine communication no problem;
Ii. progress of the respective division of labour:
Ma Yonghao: Building digital circuits, simulating circuits and commissioning
Zhang Ye Pupil: single-chip microcomputer's dual-machine communication, temperature display
Chen Zehiang: Filter, op amp circuit, 555 chip use
Third, the next step:
- To improve the transmission distance of the analog part, the former placement large, and the lm386 amplification two aspects;
- Temperature transmission of the digital part (12864 display);
- Digital transmission of single-channel voice signals:
- Purchase a separate Ad/da module, voice compression chip AMBE2000, speech coding chip CMX649
2. Refer to TI's book 4.3.5 The PN Code Spread spectrum, DDS, Ad/da, demodulation, expansion and other circuit modules to build a complete circuit (difficult on the frame)
* * Also, complete spectrum analysis topics
2nd phase 2015-7-22one, the infrared optical communication One problem
1. Analog part: complete voice transmission over two meters.
Commissioning Process: Before the distance is too short, consider two different reasons:
(1) The transmitting power is too small;
(2) Reception level amplification is not enough;
STEP1: The power and current of the transmitter and the relationship between, we will adjust the potentiometer to the maximum current position, and added a transmitter tube, found that the transmission distance does not work; Through the oscilloscope to observe the receiver of different distance receiving circuit has not been amplified signal, distance from the nearest to two meters, The receiver signal attenuation is not obvious, only about half, we conclude that the receiver signal is very faint, need to enlarge.
STEP2: So at the receiving end of the LM386 output and added a LM386 circuit amplification, but the amplification effect is not obvious, and more noise;
Step3: The last method can only adjust the transistor of the front-level amplification (before the successful commissioning, the collector has not been output), amplification with S8050 transistor, through the Multisim simulation, on the other board to build a separate circuit, separate signal source input sine wave test is not distorted, access to the simulation part, Test, the effect is obvious, can reach more than two meters.
2. Digital part: Host DS18B20 acquisition temperature, 38k carrier modulation, infrared transmission, digital infrared receiver receiver, demodulation out and baseband signal inversion, so plus inverter 74HC04, from the machine received 12864 display, baud rate 4800. Because it is high frequency, the transmission distance is certainly not a problem.
Expansion part: Voice digital transmission, most of the compression coding chip external circuit is more complex, did not find the more appropriate, has not progressed.
second, simple frequency characteristic analyzer
using DDS chip AD9854 and 8052 single chip microcomputer as control unit to generate sweep signal, supplemented by key control to achieve 1mhz-40mhz, the minimum step 100KHz range of continuous sweep output and point frequency measurement. The RLC series resonant circuit is used as the network under test. Through the AD835 multiplier and the low-pass filter to obtain the same phase component and the orthogonal component of the DC signal, ADC conversion into a single-chip microcomputer, in a single-chip microcomputer data processing, calculate the phase and amplitude, through the liquid crystal display amplitude frequency characteristics and phase frequency characteristic curve.
The DDS Signal Generator enables keying to produce up to 37MHZ sine waves.
a signal that produces a phase difference of 90 degrees is not resolved, and other functions have been implemented.
Phase solution: Then buy a DDS, under the same microcontroller control, to two DDS write different phase control words.
the output signal voltage of the DDS is-4.5 to -3.5v, does not meet the input requirements of the multiplier, requires conditioning, and adopts a voltage regulator module and adder to improve the overall voltage. 3rd Phase 2015-8-6This stage is the final stage before the publication of the list, the previous phase of the basic completion of the infrared optical communication problem and frequency characteristics of the signal source part of the analyzer. This phase is divided into two main directions:1. Speech codec, infrared codec, voice transmission2. Single-work wireless paging (high frequency)Microcontroller part continues to be familiar with the minimum system and wireless transmission module NRFcompletion: Produces orthogonal signals with AD9854, complementing the previous stage. Speech codec scheme found several, not time to implement, began to enter the high-frequency part of learning, from the oscillation, VARACTOR Diode FM to the circuit debugging, radio kit based on the familiar with the design and production of the receiving circuit. 4th Phase 2015-8-16According to this competition list to make the targeted prediction-phase-locked loop correlation, from the theoretical supplement to the material purchase, to the physical construction of debugging practice for nearly a week. The title of the contest is announced, the basic part of the instrument category is the phase-locked loop, so it is logical to choose e question. High-frequency difficulty, choose this problem less people, encountered a lot of unknown difficulties, good draw, the results are still ideal, the second in the province. This phase is mainly familiar with PLL, especially the production of loop filter, multiplier, high-frequency PCB design, ad sampling, 12864 liquid crystal display waveform and so on. first, the list compared with previous years
1, compared to previous years did not:
① minimum system without single chip microcomputer (single chip microcomputer development system only)
② no Ad/da conversion module
③ no display device
④ No op amp, comparator chip
⑤ without enameled wire
⑥ Non-distortion tester
(The sense MCU function is weakened, may compare the analog circuit of the bias)
2, the list gives:
① varactor diodes (very likely for FM)
②500m oscilloscope (High frequency)
③ Wireless Transceiver Module
④ color camera with AV terminal output (analog signal output)
⑤ Millivolt meter (instruments every year)
second, the idea
1, according to the monolithic microcomputer function weakens, as well as the variable capacitance diode, the oscilloscope 500M high frequency, thought has the possibility out FM transmit receives. The two session has not been out. May do a part, such as only to receive or launch, such as only the phase-locked loop chip frequency synthesis.
2, with AV terminal output color camera, may be out of wireless video or image transmission. Wireless video transmission of some existing products at the GHz level. The picture transmission should be in digital form. The bandwidth, real-time requirements of this direction are relatively high.
third, the question
1. The Wireless transceiver module feels like it's still on the plane.
2. Camera with no buy, three hundred or four hundred.
3. The next step is to practice direction and division. Summary1. Composition of the team. our group in addition to my other two teammates are 13 telecom base class, ability is strong, efficient, willing to endure hardship. The teacher is very responsible, regularly check the progress and discuss the next phase of the plan. Our division of labor is that two people are responsible for the hardware, one person responsible for the software. Basic from the early to the late, all our progress and plans are completed relatively smooth, the beginning of the class, the progress is slightly slow, but also give us more time to run. is a good thing. 2. Guaranteed time. Yuzhong Campus Local partial, express slow; go to Lanzhou buy also trouble; class time is not the same, training time is not uniform, time period tense and so on. These are the problems to be faced with, to develop reasonable plans and short-term goals, each person regularly complete their own part of the spare time as far as possible in the laboratory. Take the software section for example. The final scenario to be achieved is the infrared digital temperature data, 12864 display. We divided it into several pieces: ① first with Guo Tianxiang two-computer communication routines, transmission 0-f key value, digital tube display, ② ds18b20 acquisition temperature, 1602 display; ③ dual-machine communication simple characters, 1602 display; ④ to achieve the final scenario. 3. As captain. ① and teachers to do a good job of communication, lubrication, monitoring progress, planning plans, select the appropriate technical route, according to the actual situation to correct and solve some problems in a timely manner. ② ensure team harmony, work happily and act together as much as possible. ③ A lot of trivial things to solve in time, such as material tools, instrumentation and so on, to ensure normal training. 4. The process will definitely encounter problems, if it is relatively basic, do not think about the past, hide, just like if we were at that time LCD waveform, multiplier to make a bit of proficiency, the results should be better
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