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).

Development of timer based on liquid level measurement system

This paper describes the design and development of the timer based on liquid level measurement system in which timer 555 is used in astable mode. The capacitor charging time i. e. the ON time pulse width of the timer output waveform which is measured using a digital storage oscillator （DSO）,is linearly proportional to the capacitance of a co-axial cylindrical capacitive transducer, and this capacitance once again linearly varies with the change in liquid level. Hence, we obtain a linear relationship between the liquid level and the capacitor charging time. The main advantages of this developed system are linear input-output relationship, small in size, easily portable, cost effective, and independent on the ambient temperature effect. The system can also be exploited to measure dielectric constant of liquid or solid in various process industries.