Description of Inductors Elmer Station
This station provides facilities (clamps, tinning materials, extra wire/cores, LC Meter, microscope) to facilitate the builders' coil and transformer winding tasks. The Elmer should be ready to consult on:
- winding the inductors (L1 and T1)
- mounting the inductors (especially T1) on the board.
Location
This station should be located in a well-lit, bright area, preferably by a window or under a bright light.
Resources
Supplies
Item | Qty | Notes |
---|---|---|
spool of #30 thernmaleze magnet wire | 1 | |
Spare T25-6 toroid cores | 25 | |
15' hank of color coded thermaleze bifilar wire | 1 | |
spool of 63/37 solder .032" | 1 | (for tinning) |
jar of paste flux | 1 | (for tinning) |
black and yellow wire insulation | 1 | (cut into 1/8" bits to serve as identifying "sleeves" for leads) |
UNCOATED cookie sheet | 1 | (for tinning) |
Wire
Builder measures out about 15" of #30 wireWind
Builder winds L1 coil: 30 turns of #30 wire on a T25-6 (yellow) core using fingers, or skewer, or Irwin clamp. It is adviseable to leave the leads relatively long at this point in case more turns are required.Tin Leads
Builder tins coil leads to within 1/8" of core. Tinning involves using paste flux and then running the wire thru hot solder blobs on the iron(Optionally) Verify Turn COunt
Builder can use PC microscope to help verify turns count(Optionally) Test Inductance
Elmer tests the coil's inductance on LC Meter:- release all switches (on the right side of the meter)
- Push in on the "PWR" switch on the right side of the meter.
- Once calibration is completed, push in the "LX" switch on the right side of the meter.
- When meter reads "not an inductor", press and hold the push button on the top of the test harness plugged into the meter. This shorts the leads
- Push the "ZERO" button on the right side of the LC Meterand then release it
- Rrelease the pushbutton on the top
- Insert the coil's leads into the pin holes on the test harness atop the meter
- Read the inductance. It should be close to 2.5 µH (+/- 2µH) on the 20m RX's coil. Recognize that the inductance will change somewhat once it is installed onto the board and the leads are soldered and trimmed.
- release all switches (on the right side of the meter)
-
Wire for Primary and for Secondaries
Builder measures out two 7" strands of #30 wire, folding one of the wires over double and twisting it together about 3 twists to the inch Wind Primary
Builder winds transformer on a T25-6 core, using the 7" wire to wind 8 turns of #30 for the primaryWind (bifilar) Secondaries
Builder winds 4 turns of the folded over, twisted wire on top of and in the same direction as the primary.Tin and Tag the 2 Primary Leads
Builder tins (see above)and then identifies primary wilres (using bits of insulation slipped over the leads. Recommended colors:- Black insulation for primaries
- red insulation for one of the secondaries
- no insulation for the remaining secondary
Separate and Tin the 4 Secondary Leads
Builder separates and tins (see above) both pairs of secondary leadsID and Tag Secondary Leads
Builder uses DMM's continuity or ohmmeter tester to identify which leads go to which pairs and identifies them using a different color of insulationFinished
Builder returns to builder station to mount inductors per builders notes.- Turn counting - any pass through the center of the core = 1 turn
- Make sure both the primary and the bifilar secondary windings ot T1 are wound in the same direction
- L1 should end up with approximately a 15 degree "wedge" of clear core at the bottom.
Tools
Item | Qty | Notes |
---|---|---|
wooden skewers | 6 | |
Irwin Clamps, short clips | 4 | |
25W soldering iron | 1 | |
Tweezers | 1 | |
diagonal cutters | 1 | |
PC with microscope software loaded | 1 | |
PC microscope | 1 | (for verifying turn count) |
Instruments
Item | Qty | Notes |
---|---|---|
LC Meter | 1 | (optionally measuring L1 inductance) |
DMM | 1 | (identification of secondary leads) |
Process
Elmers should read/provide a copy of the Common Construction Techniques articles on Toroidal Inductors for reference. A pdf file is here for downloading and printing.