In a small model,
I will use a DC motor to generate enough voltage to turn on the transistor. Because the voltage I will generate from rotating DC motor will be not collected enough to supply 2.7 LED light, I will get the help of batteries to turn LED on.
(=The circuit sketch for this idea is illustrated below. After building/testing the circuit board, however, I realized I DO NOT need to connect anything except a generator and LEDs! Because the generator with a wheel attached creates 3 to 5 voltage.)
*SIDE NOTE* = Collecting energy (from DC motor or human power) is not a right term. Rather, generating voltage is a right term.
In a larger scale,
I will use a DC motor (larger) to generate enough (or more than enough) voltage (and energy, by human feet) to turn on the LED light. In this case, I might not need the transistor but I may need something to protect the light.