Projects start from this lecture. Lets see first project and its circuit diagram
This LED will nearly glow ON up to 3.5 secs and same OFF time.
You might sometime need to keep LED glowing for more or less time, then there is an easy solution, away from all the calculation.
Resistors (R1 = 25K, R2 = 1M, R3 = 1K).
Capacitor C1 = 4.7uf(micro farad)
555 Timer IC.
Some wires (for making jumpers/connections).
Now make the connections as shown in the above circuit diagram.
It can be used as a signal.
In any circuits you can interface with this circuit.
Many gadgets are available in market, where this circuit mostly used, i.e. Eye blinking of doll like that.
In quad-copters and cars this circuit use as an indicator.