🔌 Electronics Tools

Decode 3, 4, 5 and 6-band resistors, convert a value back into colours, and read SMD markings including EIA-96.

Enter any two of voltage, current, resistance and power and get the other two, with the rearrangement shown and a resistor power rating suggested.

Size the series resistor for one LED or a whole array, with real current, power and the parallel-wiring trap spelled out.

The real output of a resistor divider including the load it drives, plus standard E24 pairs for a target voltage and the output impedance.

Combine resistors, capacitors or inductors either way, split the voltage and power across them, and find two standard parts that hit any value.

Time constant, corner frequency, rise time and the charge curve for an RC pair, plus resonant frequency, Q and bandwidth for an LC tank.

Frequency, period and duty for a 555 astable, pulse length for a monostable, and a straight answer about why 50% duty is out of reach.

How much heat a linear regulator makes, how hot its junction gets, and whether it needs a heatsink — with the real current ceiling.

Closed-loop gain for every standard topology, plus the two ceilings that actually stop you: gain-bandwidth product and slew rate.

Real runtime from capacity and load, using Peukert's law, depth of discharge and temperature — not the optimistic capacity-over-current figure.

NTC resistance, divider voltage and ADC counts across a range — plus the temperature resolution you really get, which is nowhere near uniform.

IPC-2221 trace width for a current and temperature rise, with resistance, voltage drop and the clearance table that actually matters for safety.

Cut lengths for dipoles, verticals, J-poles and Yagis, with the end-effect factor explained and coax stub lengths that use the right velocity factor.

How much power actually reaches your antenna, and why feedline loss makes the SWR reading at the radio look better than the truth.

Whether a radio path will close: EIRP, free-space loss, received signal and margin, plus the Fresnel clearance that line of sight does not give you.

Microstepping buys smoothness, not accuracy — past 1/32 the driver counts steps the axis never takes. Plus steps/mm and driver Vref.

The rating is stall torque, about five times what you can design to — and static torque grows as arm length while dynamic grows as its square.

A boost draws more current than it delivers — and at microamp loads the "inefficient" linear regulator beats the switcher outright.

The 4.7k I2C pull-up is outside spec at 400 kHz, 16 MHz cannot hit 115200 baud, and PWM frequency trades directly against resolution.

Range rules sensors out before accuracy does — and an ultrasonic sensor drifts 24 times its own spec across an ordinary temperature swing.

A six-character locator is a 6 km box, not a point — which makes it useless for pointing below 50 km and fine beyond 250.

Farnsworth does not slow the characters — only the gaps, to 23.5:1 instead of 3:1. A Koch trainer with audio and the timing laid out.

The offset is a duplexer problem, not a convention — 2 m has the tightest fractional separation of any band, and it is the busiest.

One S-unit costs four times the power, so the whole legal range is under two. And a band can be dead overhead and open at 3000 km.

A Technician holds 22.5% of HF by bandwidth but 7% of the phone — and all of it is one segment on 10 metres.

The NATO alphabet measurably beats an improvised one — and 7 of the 10 digits are said differently, which everyone forgets.

The 74% pass mark only asks for 66% knowledge, because a quarter of what you do not know you get right anyway.

Logs are kept in UTC — which puts most of an American evening on tomorrow date. Logs contacts, exports ADIF, stays in your browser.