Monostable Timer Circuit

This circuit produces a pulse when triggered; the pulse is a given amount depending on the following equation: T = 1.1 x R1 x C1, where T is time. The circuit I am using is a slight variation to this one; the pulse is given to darlington transistor, which closes a switch until the pulse is completed. When this switch is closed another circuit is activated ie: motor, LEDs, etc. I plan to develop a switch mechanism that is activated by the movement of passing trains, traffic, and pedestrians. The switches would become the triggers for the circuit.

Parts list: 555 Timer, ULN2804 Darlington Transistor, 10 uf capacitor, 100k resistor, 27k resistor, 1k resistor, LED, dc motor, 2-9 volt batteries, and various resistors to adjust the time period. PCBoard.

PCBoard schematic:
Link: 555 Timer Circuits