Feb 022015
Wheel and Tire calculator

More about tires Tire sizes are expressed by the manufacturers with three sets of numbers: Tread width – Aspect Ratio – Wheel diameter (e.g. 215 55 R16) Automobile tires are described by an alphanumeric tire code (in American English) or tyre code (in British English, Australian English and others), which is generally molded into the [Read more]

Jan 312015
Supercapacitor discharge calculator

Super capacitor discharge time calculator. This calculator determines timekeeping operation using a super capacitor (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 [Read more]

Apr 192012
Single layer air core inductor

Single layer air core inductor 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. [Read more]

Apr 182012
Flat spiral coil inductor

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 approximationsfor 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 [Read more]

Apr 172012
Planar spiral coil inductor

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 [Read more]