calc.engineer / PCB & Electronics / Timer 555

Timer 555 v1.0.0

Calculates timing parameters for the ubiquitous NE555 / LM555 timer IC in astable (free-running oscillator) and monostable (one-shot pulse) modes. In astable mode, computes frequency, period, duty cycle, and HIGH/LOW durations from R1, R2, and C using f = 1.44 / ((R1 + 2·R2) · C). In monostable mode, computes pulse width from R and C using t = 1.1 · R · C. Standard 555 astable duty cycle is always >50%; for 50% duty cycle use a diode across R2. Useful for generating clock signals, PWM, delays, and debounce circuits. Chain from ohms_law for power calculations or resistor_color_code for component selection.

← from ohms_law← from resistor_color_codefeeds rc_filter →feeds ohms_law →feeds led_resistor →
Operating mode. 'astable' produces a continuous square wave. 'monostable' produces a single timed pulse.
Resistance R1 in ohms. In astable mode this is the charge-path resistor between Vcc and the discharge pin. In monostable mode this is the timing resistor.
Resistance R2 in ohms (astable mode only). Charge/discharge resistor between the discharge and threshold pins. Required for astable mode.
Timing capacitor in farads. Typical values range from 1 pF to 1000 µF. Use scientific notation, e.g. 1e-6 for 1 µF.
Fill in the inputs and Compute to see the structured result.

From an agent (MCP) or the API

curl -X POST https://calc.engineer/api/timer_555 \
  -H "Content-Type: application/json" \
  -d '{"mode": …, "r1_ohm": …, "r2_ohm": …}'

MCP: connect to https://calc.engineer/mcp and call timer_555.

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