I trying to create a circuit with only one 555 to send HIGH on output(3) for very short time, like 200ms, then set LOW for something like 20~30 seconds.

Then I'm just need turn on circuit, then: a) fast HIGH (~200ms) b) long LOW (~20-30s)

I already able to make a "default" 555 circuit with stable HIGH/LOW in same timing (1000ms/1000ms), but I'm getting trouble to make this with different HIGH and LOW timmings.



General approach is to separate the discharge resistor into two using diodes.


simulate this circuit – Schematic created using CircuitLab

The capacitor C2 charges through R1 + R3 and discharges through R2, ignoring diode drops and discharge transistor collector voltage when on.

Approximately, on time is proportional to R1 + R3 and off time is proportional to R2, so you can make the ratio suit your application.

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