Design Of Three-position Curve Instrument Based On FPGA

With the development of electronic products,keys have been widely used in lives,and the keys play a decisive role in the performance,comfort and working life of the whole product.The keys quality detection for mass production is a mechanical,repetitive operation by manual test is almost impossible to achieve,because manual test is poor in consistency with big error,however,the performance and life of the keys is a must be tested indicator,the curve instrument can solve this problem.But at present,the market for key detection of some of the detection accuracy is not high,and the high detection accuracy of curve instrument is usually expensive.In view of this situation,the analysis and comparison of curve instrument at home and abroad,based on the specific context of application scenarios and analyzing functionality and performance requirements of the test,this paper designed a low cost,high performance,can simultaneously measure 3 keys(3 positions)of the load displacement curve and contact resistance displacement curve of the multi-function curve.This curve instrument consists of analog signal conditioning module,analog to digital conversion module,main control module,displacement signal acquisition module,servo motor control module and data transmission module.This paper uses Altera Cyclone series FPGA as the control core,chooses conversion chip AD7689 with 16-bit to achieve load and contact resistance of keys conversion with high-precision,through the master chip port scanning high-speedly to count displacing pulse signal during the process of pressing and bouncing.Signals of three channel pressure sensor and contact resistor were input to the analog circuit for amplifying and filtering,then the amplified signals were sent to the ADC module for analog to digital conversion.The AD conversion data was read by FPGA and uploaded to PC for curve fitting and real-time display through the USB.In order to increases the curve instrument system anti-jamming capability,the paper investigates the problems of hardware anti-interference,describes the curve instrument of hardware design and software development.Experiments show that this curve instrument has good real-time performance,high precision,stability,low cost.Three keys can be detected simultaneously.This instrument can be used as a good reference for keys detection.