The Application and Stimulation Research of PIC single chip in. waveform signal generator. Gao Yi

Transcription

1 Advanced Materials Research Online: ISSN: , Vols , pp doi: / Trans Tech Publications, Switzerland The Application and Stimulation Research of PIC single chip in waveform signal generator Gao Yi (School of Mechanical Engineering of Guiyang University, Guiyang Guizhou ) Keywords: waveform signal, PIC18F4620, instruments and apparatuses, automatic test. Abstract: This article chooses PIC18F4620 as its key device and designs a waveform signal generator. It can improve the function of the waveform signal generator in hand. A lot of advantages are included in it, such as simple circuit, simple regulation and convenience maintenance. It can completely be used in industrial instrumentation and automatic testing area. Waveform signal generator is also called function generator, it can generate some certain periodic function signals, such as sine wave, square wave, saw tooth wave and triangular wave, its frequency range can be raised from several mill hertz or micro hertz to scores of megahertz. In industrial environment, this function signal generator is usually used in the area of instrument and auto control system testing; meanwhile, it is also widely used in non electric testing. Usually, we classify signal generator by various waveform signals. By different outputting waves, signal generator can be divided into sine wave generator, function signal generator, pulse signal generator and random signal generator. But function signal generator is the widest one in use, and it is also the common one, because it can output various kinds of waves to satisfy the need we want. Meanwhile, its signal frequency range is wider than others. Pulse signal generator is mainly used to test the working performance of the pulse digital circuit and to test the transient response of analogous circuit. Random signal generator is called noise signal generator too, it generates analogue noise signal of the circuit and system to test the noise characteristics 1. The function signal generator is universally used in automation of industrial production, this article adopts 51 single chips as its core to design generator. Because of the feature of 51 single chips, there are several disadvantages in the function generator such as complicate circuit, difficulty in digital adjusting and inconvenience in maintenance. So this article chooses PIC18F4620 single chip as the core to design function signal generator. With the help of the special functional module and relative components of PIC single chip, it can efficiently avoid the disadvantages that has mentioned and make modular design for its circuit. Meanwhile, it can not only generate sine wave, square wave, saw tooth wave and triangular wave, but also adjust the waves frequency signal and keep its changing orderly. The most important thing is that online debugging and online programming is available and it is not limited by single chip s clock frequency. The design goals and ideas According to the signal generator s characters and application, this article designed a simple using and high performance one with PIC single chip and high-quality converter DAC0832 and the periphery of module circuit. This signal generator could generate sine wave, square wave, saw tooth wave and triangular wave whose frequency and range can be adjusted. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (ID: , Pennsylvania State University, University Park, USA-06/03/16,21:06:52)

2 Advanced Materials Research Vols The whole system is controlled by PIC single chip, it is composed by interface circuit and designed by c programming software. It is a signal generator with multiple waves outputting and multiple functions. It is meaningful to research signal generator designing, with the help of the signal from it, we could test the performance and the parameter of the device. It can also do index checking and parameter adjusting and performance evaluation for electronic products. It is also popular in circuit transfering network, Capacitance and inductance combinatorial circuit, Capacitance and resistance combinatorial circuit, and modular frequency testing. This waveform signal generator that the article mentioned can generate square wave, saw tooth wave, sine wave and triangular wave. It depends on DAC0832 to make conversion. First, set a array some certain values in the function, then these values are outputted by digital to analog convertor, after power amplification and wave filtering, different types of waves could be showed in the oscilloscope. As the values in the array of the function are not displayed by one time, it is necessary to write the controlling word in PIC single chip to make interruption open, then the counter begin to count. Once the numbers is out of the range of the counter, the interrupt function could be called to send the values to convertor DAC0832. The continuous wave which is displayed in the oscilloscope is just based on constantly sending data. In order to generate different waveform signals, this article uses independent button switches to control the different frequency in function waves. This article also uses sliding resistor to provide convertor DAC0832 with different reference voltage to generate various rages of waves. The analyzing and designing of principal and structure. This article adopts software and hardware to design circuit, that is, this article combine software with hardware to design waveform signal generator. The advantages is that this design takes advantage of the software and hardware s characters completely and make up for their own disadvantages. It not only responses quickly and owns the character of high-performance, but also is flexible and intelligent. Combined with software and hardware, this signal generator s function is more comprehensive and the performance is more superior. The more important thing is that the function could be extended such as storing and operating waves by making program. Meanwhile, we design USB interface of the signal generator to make sure that it can do communication widely. What is shown in picture 1 is the circuit structure. When we press the selecting waves key, external interruption is happened, when digital tubes display the sequence number of the wave, the PIC18F4620 signal chip execute some certain waveform interruption programs and send data to the convertor DAC0832 regularly, then voltage waveform is acquired in outputting terminal. Then enlarge the voltage waveform with amplifier and do wave filtering by filtering circuit. After dropping high order waves, targeting waves can be displayed in the analog oscilloscope. Based on the theory before, users can change the wave frequency by pressing relative keys. With the help of the slide resister, users can change the reference voltage of the convertor DAC0832 to change electric current. That is, changing reference voltage, making the voltage to change according to changing the electric current so that the waveform range could be adjusted and the users could acquire all kinds of wave signals that are needed in science and technology experiments 2.

3 1448 Manufacturing Process and Equipment Figure one: Schematic diagram Simulation and debugging in the software PROTUES In order to debug and test the correctness and rationality of the circuit diagram, this article debugs the waveform by software PROTUES. After adding the program of the design in simulation environment of the software PROTUES and setting parameters, the waveform can be checked 3. By the selecting keys on the interface circuit, we can circularly select square wave, saw tooth wave, triangular wave and sine wave to output and make them to be displayed in the Oscilloscope. Meanwhile, the digital tube can display the number of 1 to 4 which represents current waveform. Picture 2 to picture 7 represents different kinds of waveform signal in debugging process. In simulation process, first, this article switches keys for four times to output different kinds of waveform. Then, the testers could control the frequency and sampling point by different keys, the waveform range could be changed by convertor DAC0832 which can also be changed by slide resistor. Last, waveform could be displayed on analog oscilloscope. In waveform pictures, the upper wave, the middle wave and the lower wave were acquired from the convertor outputting terminals, first-order resistance-capacitance filtering circuit outputting terminal and second-order resistance-capacitance filtering circuit outputting terminal. The goal is to explain the function of filtering circuit. The waveform which is acquired from outputting terminal may become serious step waves because of decreasing sampling points. In order to acquire idealism outputting, that could be changed by filtering waves. For the sine wave, it is be outputted by the third outputting style in the practical application. For the square wave, it should be outputted by the first outputting style. For saw tooth wave and triangular wave, any of outputting style is available 4. Figure two: Sinusoidal wave (The order is: The original output.the first order RC filter output. The second order RC filter output) Figure three: Square wave

4 Advanced Materials Research Vols Figure four: Sawtooth wave Figure five: Triangular wave Figure six: Amplitude modulation Figure seven: Amplitude modulation (fractionated gain) There are two ways in the whole frequency adjustment process. One is changing numerical sampling method, that can not change the waves continuity and smoothness. The other one is changing the interval of the sampling points. The narrow the interval is, the smoother the wave becomes. Broadening the interval, although outputting waves frequency is enlarged, waveform is dispersed, if testers wants to make the waves slide, it is needed to do wave filtering 5. Form the consequence of simulation in software PROTUES, this article realized the wave outputting of four kinds of low frequency of signals and testers could adjust the frequency and range of them. For frequency adjusting, when clock frequency is under 40MHz, sine wave, saw tooth wave and triangular wave can keep their shapes in the range of 0KHz to 5KHz. Square wave s max shape keeping range may reach to 30KHz. For range adjustment, the four kinds of waveforms range could be adjusted continually under the voltage of 0V to 5V. It can completely satisfy the requirement of automatic industry. Author introduction: Gao Yi,1978-,male,Miao nationality, guiyang, guizhou,lecturer, master, mechanical engineering and automation major, gygyky@126.com. Tel: References: [1] Yanming Bai.51typical examples of system development essence Publishing House of electronics industry(2009). [2] Shusheng Peng.Zhihong Zhuang. The principle of PIC single chip microcomputer andapplication Machinery Industry Press(2006). [3] Juan Liu. Singlechip C language and PROTUES simulation training.34-38(2008). [4] Chao Ma. Handbook of theory and application of ATmega Tsinghua University press(2003). [5] Rongzheng Li. Qizhong Liu.Xuejun Chen. PIC microcontroller principle and application (third edition). Beijing Aerospace University Pres(2006).

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