As Mozikluv suggested 555 could be connected as a monostable pulse generator as shown in my schematic. Here the monostable timing period is initiated by a falling edge (i.e.a high to low transition) applied to the trigger input (pin 2). When such an edge is received and the trigger input voltage falls to below 1/3 of the supply voltage, the 555 output (pin 3) goes high and the monostable pulse is generated for a period determined by the time constant C X R. The amplitide of the pulse will be approximately equal to the supply voltage. The period for which the out put is high is = 1.1 RC. Hope you understand
Cheers !