Toroids

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 in transformers for Diode Ring
  Mixers. Ready built and homebrew.
• Many Others

6
Toroid Specification
7
Toroid T37-2

ofTurns Inductancein uH lengthin inches includes1 inch tails
6 .11 5.0"
8 .20 6.0"
10 .31 7.0"
12 .44 8.0"
14 .60 9.0"
16 .78 10.0"
18 1.0 11.0"
20 1.2 12.0"
22 1.5 13.0"
24 1.8 14.0"
26 2.1 15.0"
28 2.4 16.0"
30 2.7 17.0"





Physical Dimensions OD 0.375 in. / 9.53 mmID 0.205 in. / 5.21 mmHt 0.128 in. / 3.25 mm
Magnetic Dimensions 2.31 cmA 0.064 cm2V 0.147 cm3
Dimensional Tolerance OD - /- 0.015 in.ID - /- 0.015 in.Ht - /- 0.02 in.
ALuH (AL Turns2) / 1000 3.0
Basic Iron Powder Carbonyl SF
Material Permeability (µ) 8.5
Temperature Stability (ppm /C) averaged from -55C to 125C 35
Magnetic Tolerance tested with evenly-spaced windings /- 5
Toroidal Color Code Yellow/Clear
Resonant Circuit Frequency Range range is given to optimize Q and core loss 3MHz - 40MHz

 
8
Toroid Table

material 1  u20  0.5-5 MHzmaterial 2  u10  2-30 MHzmaterial 6  u8.5  10-50 MHzmaterial 10  u6  30-100 MHzmaterial 61  u125  0.2-15 MHzmaterial 43  u850   material 1  u20  0.5-5 MHzmaterial 2  u10  2-30 MHzmaterial 6  u8.5  10-50 MHzmaterial 10  u6  30-100 MHzmaterial 61  u125  0.2-15 MHzmaterial 43  u850   material 1  u20  0.5-5 MHzmaterial 2  u10  2-30 MHzmaterial 6  u8.5  10-50 MHzmaterial 10  u6  30-100 MHzmaterial 61  u125  0.2-15 MHzmaterial 43  u850   material 1  u20  0.5-5 MHzmaterial 2  u10  2-30 MHzmaterial 6  u8.5  10-50 MHzmaterial 10  u6  30-100 MHzmaterial 61  u125  0.2-15 MHzmaterial 43  u850   material 1  u20  0.5-5 MHzmaterial 2  u10  2-30 MHzmaterial 6  u8.5  10-50 MHzmaterial 10  u6  30-100 MHzmaterial 61  u125  0.2-15 MHzmaterial 43  u850   material 1  u20  0.5-5 MHzmaterial 2  u10  2-30 MHzmaterial 6  u8.5  10-50 MHzmaterial 10  u6  30-100 MHzmaterial 61  u125  0.2-15 MHzmaterial 43  u850  
Size-gt T37 T44 T50 T68
AL-gt 40  30  55.3  420 52  42 100  49  40  31  68  523 57  47
Turns Inductance in uH, and length in inches Inductance in uH, and length in inches Inductance in uH, and length in inches Inductance in uH, and length in inches
6 .14  .11  1.99  15.1  5.00" .19  .15 .18  .14  2.45  18.8  5.75" .21  .17  6.50"
8 .26  .19  3.54  26.9  6.00" .33  .27 .31  .26  4.35  33.5  7.00" .37  .30  8.00"
10 .40  .30  5.53  42.0  7.00" .52  .42 .49  .40  6.80  52.3  8.25" .57  .47  9.50"
12 .58  .43  7.96  60.5  8.00" .75  .60 .71  .58  9.79  75.3  9.50" .82  .68  11.00"
14 .78  .59  10.8  82.3  9.00" 1.0  .82 .96  .78  13.3  102  10.75" 1.1  .92  12.50"
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
• Dont 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 Dont 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