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Electronics calculators
8 of them, and every one shows the formula it used and says when the answer is a problem — a resistor that will cook, a MOSFET that needs a heatsink, a cable losing more than it should. Units are a dropdown, so there is no converting to do in your head.
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- Ohm's law calculatorEnter any two of voltage, current and resistance to get the other two, plus the power dissipated and whether a quarter-watt resistor will survive it.Explained in: Ohm's law and power
- Resistor colour code calculatorClick the bands you can see and read off the value, the tolerance range and the schematic notation. Handles 4, 5 and 6 band resistors.Explained in: Resistor colour code
- LED resistor calculatorThe series resistor for any LED and supply, rounded up to a value you can actually buy, with the real current and a warning if it will cook.Explained in: LEDs and the series resistor
- Voltage divider calculatorOutput voltage from two resistors, plus the current the divider wastes and why the load changes the answer.Explained in: Ohm's law and power
- Voltage drop calculatorHow much voltage a cable run loses, and what is really left at the load. Counts both legs of the circuit, which is where most people go wrong.
- Capacitor calculatorDecode a printed code like 104, then get reactance at frequency, RC time constant, charge and stored energy.Explained in: Capacitor codes and markings
- 555 timer calculatorAstable frequency, duty cycle and high and low times from R1, R2 and C — or the pulse length of a monostable, with warnings on the resistor range.Explained in: The 555 timer: astable and monostable
- MOSFET power calculatorConduction loss from Rds(on) and drain current, the voltage lost across the part, and the junction temperature that decides whether it needs a heatsink.
A calculator that gives a number and no reasoning teaches nothing, and a viva panel will ask you where the number came from. Each of these links back to the write-up in the Knowledge Base.