555 IC Timers

Pin 5

Control Voltage: Usually connected to a 0.01uF capacitor, then the ground. The capacitor smooths out fluctuations from the supply voltage that will affect the timer.

Pin 7

Discharge: This pin discharges the capacitor that controls the timer. the discharge is usually connected to the ground through a capacitor.

Pin 1

Ground: Connects the timer to the ground.

Pin 3

Output: Transfers the clock signals to the circuits load (ex. LED)

Pin 4

Reset: Will restart the timer's operations when grounded. It is connected to the supply voltage, and when it is grounded, it will turn off the timer.

Pin 8

Supply Voltage: Provides voltage for the timer to run. The voltage must be 4.5-15V DC.

Pin 6

Threshold: This pin monitors the voltage across the capacitor connected to the discharge. When the threshold reached 2/3 supply voltage, pin 3 goes LOW.

Pin 2

Trigger: When the voltage to the trigger drops to below 1/3 of the supply voltage (going LOW), the output will go HIGH.