A small bench for the everyday conversions. Watts, amps, volts, and ohms, solved as you type. DC and resistive loads use a power factor of 1. For AC, set the power factor.
On the bench
Watts to amps — I = P / (V × PF)
Amps to watts — P = V × I × PF
Watts to volts — V = P / (I × PF)
Ohm's law — V = I × R, I = V / R, R = V / I
Power and ohms — P = I² × R, or P = V² / R
Z80 hub — Zilog Z80 history, John Winans Z80 Retro!, Chinese modular educational builds, CP/M, and a curated link directory.
Circuit explorer — a beginner trainer for loops, Ohm's law, series, parallel, LEDs, diode I-V, capacitors, RC time, voltage dividers, Kirchhoff, Thévenin, Norton, Superposition, mesh/nodal, BJT CE bias, and MOSFET/FET as a voltage valve (18 lessons).
Resistor codes — click the bands or look up ohms; 4-band decoder with E24 snap.
LED resistor — supply, Vf, and milliamps in; series ohms and nearest E24 out.
Voltage divider — Vin, R1, and R2 in; Vout, current, and power out.
Current divider — parallel branches share Iin; I1, I2, Req, and power out.
Series & parallel — combine ohms in series or parallel; Req and nearest E24.
RC time — τ = R × C; 1τ / 3τ / 5τ charge marks and corner scale.
RL time — τ = L / R; 1τ / 3τ / 5τ current marks and corner scale.
Reactance — f and C or L in; Xc or Xl, |Z|, and phase out.
LC resonance — f₀ = 1/(2π√(LC)); ω₀, Z₀, and series Q / bandwidth when R > 0.
Capacitor codes — EIA 3-digit marking decoder; look up pF / nF / µF with E12 snap.
Inductor codes — EIA/IEC 4-band color decoder; look up µH / mH / H with E12 snap.
RC filter — low-pass or high-pass; fc = 1/(2πRC), gain and phase at a chosen f.
RL filter — low-pass or high-pass; fc = R/(2πL), gain and phase at a chosen f.
Turns ratio — ideal transformer Vp/Np/Ns → Vs (and Is); mutual M = k√(L1 L2).
Impedance — series or parallel R+L+C; |Z| and phase from f, R, L, C.
Q-factor — series or parallel RLC; f₀, Z₀, Q, bandwidth, and −3 dB band edges.
dB / dBm — power and voltage ratios in dB; dBm ↔ mW and dBW ↔ W.
Op-amp gain — inverting, non-inverting, and ideal differential; Av in V/V and dB, optional Vin → Vout.
555 timer — NE555 astable and monostable; frequency, period, duty, and pulse width from R and C.
Wheatstone bridge — Vin and four arms; Va, Vb, Vg, and balance; solve R4 when balanced.
Schmitt / comparator — ideal comparator and Schmitt trigger; thresholds, hysteresis, and HIGH/LOW state.
Peak detector — diode + C hold (or ideal precision); Vhold, ripple ΔV ≈ I/(fC), and τ from Rload.
Rectifier — half-wave / full-wave / bridge; peak Vout, fr, and ripple ΔV ≈ I/(fr C) live.
Zener regulator — shunt clamp; Vin, Vz, Rs, Rload → Vout, Iz, and power live.