Power supply design for automotive electromagnetic valve quality testing

Is used in the design of automotive electromagnetic valve quality testing power supply EDNadmin times solenoid valves are widely used in modern cars, the performance of the solenoid valve is closely related to the performance of the car. When applied to the power of the solenoid valve in the actual work condition is complicated, mainly displays in electromagnetic valve power supply voltage amplitude, frequency, duty cycle, the complexity and randomicity. In order to guarantee the quality of the electromagnetic valve factory, this paper has designed and produced a convenient to simulate electromagnetic valve actual working state of power supply. In accordance with the requirements of electromagnetic valve's work in the car, the electromagnetic valve under various working condition of simulated test quality requirements. At the same time solve the problem of test export solenoid valve product performance indicators, for our country to export products to provide the necessary technical performance of solenoid valve testing equipment. System structure and working principle as shown in figure, the whole system consists of single chip microcomputer, I/O expansion circuit, D/A conversion circuit, PWM circuit, frequency selective circuit and photoelectric isolation and drive circuit and the keyboard and display circuit. System with the single chip processor as the control center, using DDS chip AD and PWM control chip SG for waveform generating equipment, using A extension microcontroller peripheral interface as three-way data input port D/A conversion circuit, three analog voltage are used to control the frequency, duty cycle and amplitude. By single chip microcomputer control waveform data processing equipment frequency and duty ratio of the output signal, again through the level after frequency selection and optical coupling isolation circuit and driver circuit, realize the output frequency, duty cycle and amplitude adjustable PWM signal. In addition, the man-machine interface using keyboard and LCD display, through the RS after a serial port communication, implemented by a PC. Signal and control circuit design of system requirements between O ~ Hz frequency adjustable duty ratio of PWM signal, using PWM control chip SG can be easily produced independent adjustable frequency and duty ratio of PWM signal, but as a result of SG in Hz frequency unstable, so need to design the signal is divided into two frequency, which is O ~ Hz low frequency band, the AD as a signal generator, high frequency band to ~ Hz, the SG as a signal generator. Low frequency PWM signal generating circuit AD is high integration of direct digital frequency synthesizer, the device width, frequency and phase are controlled. The main composition of the phase accumulator, phase addition, waveform storage, digital multiplier and D/A converters. Under the control of basic work for the sampling clock signal, through controlled by frequency code phase accumulator output phase code, will be stored in the read only memory (ROM) of the waveform sampling read data values according to certain rules, through D/A conversion and output sine signal after low pass filter. Design of low frequency signal circuit, as shown in the circuit, AD converter MHz active crystal up for reference frequency source. As I/O output data RESET of the AD, FQ_UD, W_CLK control. For low frequency PWM signal output port. SCM specific input methods for effective RESET signal RESET input data address pointer to the first input register, W_CLK rise along in the first set of data, Pointers to the next input registers. A consecutive W_CLK rise along the complete control of data input. Since WCLK signal rise along the invalid. FQ_UD rise along comes the control data from the input registers in frequency, phase control registers, update the output frequency and phase, at the same time the address pointer is reset to the first input register, waiting for a new set of data to write. The first page of the first page, pp