555 Timing Circuit Calculator and Formulas
555 Square Wave Calculator
Input Parameters:R1 (ohm); R2(ohm); C(F)
Output parameter: Duty cycle(%), High level time(s),Low level time(s), Frequency(Hz)
Calculation formula:
TH (High level time s) = 0.693 * (R1 + R2) * C
TL (Low level time s) = 0.693 * R2 * C
Frequency(Output frequency) = 1.44 / ((R1 + R2 + R2) * C)
DCP(Duty Cycle %) = (T(h) / (T(h) + T(l))) * 100
The circuit that can play a timing role of the 555 timer is a monostable circuit.
The monostable circuit is a basic pulse unit circuit with two working states: steady state and transient state. When there is no external signal trigger, the circuit is in steady state. When triggered by an external signal, the circuit flips from steady state to transient state, and after a period of time, the circuit automatically returns to steady state. The length of the transient time depends on the parameters of the circuit itself, and has nothing to do with the length of the trigger signal action time. The 555 timer plays a timing role in the circuit, triggering the transition from steady state to transient state.