#rc-filter

First-order RC and RL passive-filter design as an API, computed locally and deterministically. The lowpass and highpass endpoints take a resistor and capacitor (RC) or a resistor and inductor (RL) and return the −3 dB cutoff frequency (fc = 1/(2πRC) for RC, R/(2πL) for RL), the time constant (τ = RC or L/R) and the angular cutoff; pass a frequency as well and they add the magnitude response as a linear gain and in decibels and the phase shift in degrees — a 1 kΩ / 1 µF low-pass has fc ≈ 159.15 Hz, and right at the cutoff the gain is −3.01 dB with −45° phase for a low-pass or +45° for a high-pass. The component endpoint solves the missing one of fc, R and C from the other two (fc = 1/(2πRC)), so you can size a resistor or capacitor for a target cutoff. All quantities are SI: ohms, farads, henries and hertz. Everything is computed locally and deterministically, so it is instant and private. Ideal for electronics, audio, embedded, signal-processing and EE-education app developers, filter-design and circuit-sizing tools, and maker software. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is first-order single-pole filter design; for full RLC impedance and resonance use an impedance API and for stored capacitor energy a capacitor API.

api.oanor.com/rcfilter-api

AC reactance and LC/RC tuning maths as an API, computed locally and deterministically. The reactance endpoint computes the capacitive reactance Xc = 1/(2πfC) and the inductive reactance Xl = 2πfL at a given frequency, and — when both a capacitor and an inductor are supplied — the net series reactance X = Xl − Xc, whether the circuit looks inductive, capacitive or resonant, and the impedance magnitude. The resonant endpoint computes the LC resonant frequency f₀ = 1/(2π√(LC)), or, given a target frequency and one component, solves the other component you need to tune to it. The cutoff endpoint computes the RC or RL filter cutoff frequency — fc = 1/(2πRC) for RC, fc = R/(2πL) for RL — and the time constant. Frequencies are in hertz; capacitance, inductance and resistance accept SI base units with handy µF/nF/pF and mH/µH inputs. Everything is computed locally and deterministically, so it is instant and private. Ideal for electronics, RF, audio-filter and embedded app developers, tuning and filter-design tools, and electronics education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is AC reactance & LC/RC tuning; for LED series-resistor sizing use an LED-resistor API and for VSWR and impedance match use a VSWR API.

api.oanor.com/resonance-api