This water heating calculator can help you determine both the amount of heat required to raise the temperature of some water (H2O) and the time it will take. It considers the heat capacities of all three states of matter, so it also works if you want to melt the ice or boil water or heat steam. This calculator uses the …

Read More »# Calculators

## LED series resistor calculator

In electronics, an LED circuit or LED driver is an electrical circuit used to power a light-emitting diode (LED). The circuit must provide sufficient current to light the LED at the required brightness, but must limit the current to prevent damaging the LED. The voltage drop across an LED is approximately constant over a wide range of operating current; therefore, …

Read More »## Supercapacitor-Ultracapacitor discharge characteristics calculator

Super capacitor discharge time calculator. This calculator determines timekeeping operation using a supercapacitor (ultracap) based upon starting and ending capacitor voltages, discharge current, and capacitor size. Formulas used: Bt(seconds) = [C(Vcapmax – Vcapmin)/Imax] This formula is valid for constant current only. Bt(seconds) = -log(Vcapmin/Vcapmax)(RC) = t This formula is valid for linear current only (simple resistive load). Edit the input …

Read More »## Multilayer air core inductor design calculator

The formula used in this calculation is from the famous Harold A. Wheelers approximations which is accurate to <1% if the cross section is near square shaped. $$L(\mu H)=\frac{31.6*N^2*r1^2}{(6*r1+9*L+10*(r2-r1))}$$ where… Please note that the diameter is measured from center of wire trough center of the coil and to center of the wire on the opposite side. Inductance (L): uHmHH Coil …

Read More »## Single layer air core inductor design calculator

Winding the wire in a single layer produces an inductor with minimal parasitic capacitance, and hence gives the highest possible self-resonant frequency (SRF). Striving to obtain a high SRF and low losses is the key to producing coils which have radio-frequency properties bearing some useful resemblance to pure inductance. The calculation is based on Harold A. Wheeler’s 1928 formula for …

Read More »## Flat spiral air core inductor design calculator

This is an popular coil geometri used in todays wireless charger circuits. The formula used in this calculation is based on the Harold A. Wheeler approximations for air core flat spiral coil inductor. …where: 1 inch = 0,0254m=2,54cm = 25,4mm. This formula applies at ‘low’ frequencies (<30MHz) using enameled copper wire. Some people call it “magnet wire”. Click on image …

Read More »## Planar spiral coil inductor design

The first approximation is based on a modification of an expression developed by Wheeler; the second is derived from electromagnetic principles by approximating the sides of the spirals as current-sheets; and the third is a monomial expression derived from fitting to a large database of inductors (and the exact inductance values). All three expressions are accurate, with typical errors of …

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