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Toroids

Toroids. An Introduction By Nicolas - M1HOG. What is Toroid?. Doughnut shaped object whose surface is a torus. Its annular shape is generated by revolving a circle around an axis external to the circle. What is a Toroidal Inductor?.

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Toroids

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  1. Toroids An Introduction By Nicolas - M1HOG

  2. What is Toroid? • Doughnut shaped object whose surface is a torus. Its annular shape is generated by revolving a circle around an axis external to the circle.

  3. What is a Toroidal Inductor? • A coil of insulated wire, usually wound round a core of iron or similar metal in a doughtnut shape.

  4. Why use Toroids? • High performance • They can be mounted closely together • Can be made in a wide range of values and characteristics • Simple to make • Q – High Quality factor (or Q) • Economic!

  5. Example Uses • RF Chokes - An inductor designed to have a high impedance to RF current and low impedance to DC current. • Transformer / impedance matching • Variable-frequency oscillator (VFO) - The frequency is set by a tuned circuit using capacitors and inductors. The frequency can be changed by adjusting the components in the tuned circuit. • Band pass filter - Small capacitor used to tune • Mixers - Used intransformers for Diode Ring Mixers.Ready built and homebrew. • Many Others

  6. Toroid Specification

  7. Toroid T37-2

  8. Toroid Table

  9. Toroids In Circuits L3 Single winding

  10. Toroids In Circuits T3 Bifilar winding

  11. Construction - Before we start • Counting turns, each pass through the core counts as one turn • Coverage 85% • Neatness is not generally critical. But get a tidy result and it makes any subsequent checking easier! • Wind in the same direction (sometimes direction matters) if only to get the coloured sides all facing the same way! • US vs UK wire sizes – Conversion tables • Ideally use wire with a heat strippable insulator

  12. Construction – Tools • Standard workshop tools • Pliers - fine • Soldering iron • Cutters • Vice / blu-tack etc to hold toroid while tinning leads etc • Magnifier - Ideally illuminated • Storage - If you are working on a few toroids; to avoid having to recount turns – was that one 32 or 38 and which core was it wound

  13. Construction - Winding • Remember every pass through the core counts as a turn • Over wind by 3 turns and remove these when complete • Pull each turn against the core to ensure it is tight. • Thread using a Blunt Darning needle. Not tried this technique myself but some recommend it • Don’t rush

  14. Construction – Bifilar Winding • Twisting the wire • 6 to 8 turns per inch • Different colour wires can be used

  15. Construction – Preparing the leads • Ideally use wire with a heat strippable insulator • Can be stripped with sand paper or a craft knife • Strip them back close to the toroid

  16. Construction - Testing and Measuring • The Atlas LCR automatically identifies and analyses almost any passive component (Inductor, Capacitor or Resistor). Inductance from 1uH to 10H, Capacitance from 1pF to 10,000uF and Resistance from 1ohm to 2Mohm. Atlas Component Analyser

  17. Construction - Installation • Pliers to pull the leads through the PCB holes tightly, solder then reheat the joint pulling the wire through to get it tight. • Triple check the wiring before cutting of surplus leads. Can be difficult to reinstall with trimmed leads!

  18. Construction - Stability

  19. Construction – Don’t Rush • Take a break, it does not have to be a marathon! • The 30 toroids for this band pass filter board were completed over several lunchtimes, and bottles of beer.

  20. Suppliers • G-QRP - http://www.gqrp.com/ • Jab - http://www.gqrp.com/ • Sycom - http://www.sycomcomp.co.uk/ • Toroid Kits - http://qrpkits.com/(Favorable rate exchange rate!)

  21. Credits SADARS Elecraft GM1SXX GW4ALG G-QRP Club Wikipedia W8DIZ Goose Island IPA And Many Others!

  22. Thank you ! This presentation is available at www.M1HOG.com

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