555 voltage control of monostable operation and simple time measurement

Left Side is ordinary 555 monostable timer,and Right Side is the output pulse width time measuring circuit. Output pulse is converted to 1V-pulse with zener diode and 1uA/V voltage current convertor is charging the 1uF capacitor . The voltage of capacitor is directly proportional to the time(seconds) of pulse width.1V=1sec.(v=1/c[idt) 5-pin of 555 is voltage control pin.Usually the voltage of 5-pin is fixed 2/3*Vcc(in this circuit it is 3.33V). By changing this 5-pin voltage we can change the monostable timer time. In R=1Mohm and C=10uF we can calculate the pulse width=1.1RC(11sec). When the switch of 5-pin is OFF, time measuring capacitor's voltage will show 11.2V(11.2s). When the switch is ON ,5-pin is applied the outside voltage. For example we apply 4.9V to 5-pin, the timer's time will extends to 76.7s(76.7V). Change the control voltage from 1V to 4.9V, then you can see the　time extention. (Don't forget the reset of the charge of 1uF)

published 9 years ago