IC 555








555 is a very commonly used IC for generating accurate timing pulses. It is an 8pin timer IC and has mainly two modes of operation: monostable and astable. In monostable mode time delay of the pulses can be precisely controlled by an external resistor and a capacitor whereas in astable mode the frequency & duty cycle are controlled by two external resistors and a capacitor. 555 is very commonly used for generating time delays and pulses.





Pin Description:

 Pin No  Function  Name
1 Ground (0V) Ground
2 Voltage below 1/3 Vcc to trigger the pulse Trigger
3 Pulsating output Output
4 Active low; interrupts the timing interval at Output Reset
5 Provides access to the internal voltage divider; default 2/3 Vcc Control Voltage
6 The pulse ends when the voltage is greater than Control Threshold
7 Open collector output; to discharge the capacitor Discharge
8 Supply voltage; 5V (4.5V – 16 V) Vcc



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