Features of calculation of power supply chokes

histeresis02Very often, beginner radio amateur has a need for calculating the choke on a ferrite toroid core for switching mode power supply or another circuit in which high currents circulate. In this case, by requesting a "calculation of inductance on a ferrite ring", it is very likely that he will be redirected to our online calculator. Using this calculator or the Coil32 app to calculate the inductance of the choke, ham radio often gets the results didn't match with the handbooks nor didn't match with the practical results. At the same time, it may even result in the burnout of transistors and curses against the Coil32's developers. What's the matter? Let's see...

Helical resonator bandpass filter

HelicalNotchSpiral resonator - is a coaxial trasmission line with the inner conductor rolled into a helix. This is the correct definition. On the other hand it can be seen as a high-Q shielded inductor that operates at a self-resonance frequency. The shield introduces additive in distributed capacitance of the coil and reduce its resonant frequency. Despite the fact that the filter on the spiral resonators difficult to compete with SAW-filters, especially in terms of sizes, interest to its has not diminished since. They allow radio-enthusiasts to create a linear narrowband filter.

Spiral resonator has invented by Alexander Horvath in 1950, but the first method of calculation was published in 1967 in the book "Handbook of Filter Synthesis" by A.I.Zverev. We will view it here very briefly with adaptation to metric measurement units. See more in the original book.


How to make homebrew
coil inductance

homebrew coilFor beginning hams it would be desirable to tell about features of coil inductors design a little. The basis of any coil is any pipe, named the coil-former on which the wire in the form of a spiral is wound. Normally beginning radio amateur repeats a construction in which description it is specified that it is necessary to wind N-turns on a former in diameter D. But it is very frequent the necessary coil-former available is not present, and there is another. Then there are following questions:

  1. How many turns it is necessary to wind on other former?
  2. Is this former suit and how device characteristics will be changed?

High frequency chokes

VHF-chokesThan the choke differs from the inductance coil? Practically anything! However it has specific features, differently for such element would not invent a special name.

The choke's main destination – to create high AC resistance ( blocking – "choking" from it) and to pass lost-free DC. Impedance of the coil inductance is defined under the formula:

XL = 2πƒL

Color coding inductors

colored marking chokeThe electronic color code was developed in the early 1920s by the Radio Manufacturers Association (now part of Electronic Industries Alliance (EIA)), and was published as EIA-RS-279. The current international standard is IEC 60062.

The EIA standard for cylindrical inductors specifies 4 coloured bands that encodes the nominal value of inductance and the tolerance, i.e. permissible deviation from the specified nominal value. The most commonly used coding 4 or 3 colored rings or dots.

About an oscillator circuit for beginners

LC-circuit For beginning radio-amateurs it would be desirable to give a few information about parameters of LC oscillator circuit. After all coil inductance is the base of it. An oscillator circuit, as it is known, consists from coil inductance and condenser.

The main characteristics of a LC oscillator circuit are: contecv

  • Resonance frequency
  • Q - factor
  • Equivalent resistance
  • Bandpass range



Wire gauge chart

There are many different wire gauge designations. AWG = American Wire Gauge, SWG = Imperial Standard Wire Gauge - (British legal standard), B&S = Brown & Sharpe, International standard wire sizes (IEC 60228) etc.

In the American Wire Gauge(AWG), diameters can be calculated by applying the formula

D(AWG)=0.005·92((36-AWG)/39) (inch).

For the 00, 000, 0000 etc. gauges is using: -1, -2, -3. This means that in American wire gage every 6 gauge decrease gives a doubling of the wire diameter area, and every 3 gauge decrease doubles the wire cross sectional area. Just like "dB" in signal levels!
In the Metric Gauge scale, the gauge is 10 times the diameter in millimeters, so a 50 gauge metric wire would be 5 mm in diameter.

Coil Winding Machine

US $187.53
The system consists of individual components including a controller, a stepping motor, a foot switch, power adapter and output shaft. This design makes it very easy for you to integrate the system into your own project.

LC Meter LC200A

US $37.99
Measuring Capacitance Range:
0.01 pF - 100mF
Measuring Inductance Range:
0.001 uH - 100H
Measurement accuracy:1%.

RF Inductors

US $6.43
Variable Ferrite Core Inductor coil set 3.5Turns 25-100MHZ

Auto Ranging LCR Meter

US $63.07
Meter can measure 0.00pF to 100.00mF capacitance, 0.000uH to 100.00H inductance and 0.00? to 10.000M? resistance. Very suitable for small value capacitor and inductor measurement.


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