555 timer IC is an IC (chip) apt for Timer, pulse generation, and oscillator applications. The 555 prone to provide time delays, as an oscillator, and as a Flip-Flop element. Ic 555 name dope as there is three 5-Kiloohm resistor combine in series in an internal circuit of IC. It consists of 16 resistors,20 transistors, 2 diodes, a flip-flop, and many other circuits. This ic operates in three different modes.
- Astable (free-running) mode – the 555 operate as an electronic oscillator. Uses include LED and lamp flashers, pulse generation, logic clocks, tone generation, security alarms, PPM and so on. The 555 used as a simple ADC, converting an analog value to a pulse length (e.g., selecting a thermistor as timing resistor allows the use of the 555 in a temperature sensor and the period of the output pulse determined by the temperature).
- Monostable mode – in this mode, the 555 functions as a “one-shot” pulse generator. Applications include timers, missing pulse detection, bounce-free switches, touch switches, a frequency divider, capacitance measurement, Pulse width modulation (PWM) and so on.
- Bistable (Schmitt-Trigger)mode – the 555 operate as a flip-flop if the DIS pin is connected and a capacitor is not included. Uses include bounce-free latched switches.
This combined with a decade counter for counting purpose also. For more details visit the below link and get the IC at a cheap cost.