Development of OPTO-LDR coupled timer based voltage to frequency converter

This paper describes the development of a timer based voltage to frequency converter(V FC).Timer LM555is used in astable multivibrator mode with two OPTO-LDRs(light dependent resistors)in the circuitry.The frequency of timer output waveform which is measured using a digital storage oscillator(DSO)is almost linearly proportional to the applied input voltage.Hence we obtain a linear relationship between the frequency of timer output waveform and the input voltage.Because of its quasi-digital output,the main advantages of this developed converter are linear input-output relationship,small size,easy portabilityand high cost performance.In addition,the timer output waveform can be directly interfaced with personal computer or microprocessor/microcontroller for further processing of the input voltage signal without intervening any analog-to-digital converter(ADC).

漫反射全息摄影实验中曝光方法的自动化设计

基于单片机技术对全息摄影实验中的曝光过程进行自动化改进,设计并制作成一个根据光强大小自动调控曝光时间的控制开关。该开关通过光敏电阻阵列采集光强信息、将数据送入单片机计算得到曝光时间、进而控制光源前面的开关,具有成本低、精度高的特点,可根据光照的明暗选择合适的档位以提高精度,弥补了实验中曝光时间统一化的不足,提高实验成功率,还可以直接使用到如“马吕斯定律的验证”等其他光学相关的大学物理基础实验中。