Astable

Astable 555 Oscillator

555 circuit diagram 50% duty cycle

50% Duty Cycle Frequency Equations

Resistor R1 needs to be sufficiently high enough to ensure it does not interfere with the charging of the capacitor to produce the required 50% duty cycle, resistor R1 connected to VCC should be no more than 10x and no less than twice R2 to the output.

2Hz 555 LED flasher circuit

555 PCB layout example

C1 – based on time delay calculations

C2 – 0.01-µF bypass capacitor for control voltage pin

C3 – 0.1-µF bypass ceramic capacitor

C4 – 1-µF electrolytic bypass capacitor

R1 – based on time delay calculations