Electronics Calculators

Robot builders do the same small electronics sums over and over: the resistor for an indicator LED, the divider that lets a 3.3 V microcontroller read a 12 V battery, the value of the unlabelled part in the bottom of the parts box. The Electronics Calculators collect those sums in one place.

What is included

• Ohm's law and power: enter any two of voltage, current and resistance, and get the third plus the power, with sensible units.
• Voltage divider: solve for the output voltage, or for the bottom resistor that gives the output you need, and see how much current the divider wastes.
• Resistor colour codes: decode 4-, 5- and 6-band resistors, or go the other way and find the bands for a value such as 4.7k.
• Capacitor codes: decode three-digit codes such as 104, R-codes such as 4R7, tolerance letters, and the voltage prefixes used on film capacitors, such as 2A222J.

Why we built it

Most online calculators handle one of these jobs and are buried under adverts and pop-ups. We wanted a fast, clean page that works on a phone at the workbench and explains its formulas, so you learn the method instead of just copying a number.

How it is tested

Each calculator is checked against hand calculations and standard tables: the E-series values and IEC colour code for resistors, and the EIA three-digit code for capacitors, including the special multiplier digits 8 and 9 that many simple decoders get wrong.

Open the Electronics Calculators. The guides below cover the theory behind each one with robot-specific examples.