The 555 timer is capable of being used in astable and monostable circuits. In an astable
circuit, the output voltage alternates between VCC and 0 volts on a continual basis.
By selecting values for C, R1 and R2 we can determine the period/frequency and the duty cycle. The period is the length of time it takes for the on/off cyle to repeat itself, whilst the duty cycle is the percentage of time the output is on. ie. T1/T. In this type of circuit, the duty cycle can never be 50% or lower. ![]() |
Notes:
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