Making a Simple Air Core Inductor (Induction Coil)

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Introduction: Making a Simple Air Core Inductor (Induction Coil)

About: I am a freelance design engineer and drummer. My business site is at http://www.zero-waste.co.uk and is often concerned with appropriate technologies, open source design and design for sustainability.

This instructable will tell you how to make a simple small air core inductor, specifically for Niftymitter. Niftymitter is an open source FM transmitter based on Tetsuo Kogawa's Simplest FM Transmitter,  a free running oscillator circuit, hence the need for a coil.

Step 1: What You Need

A small reel of enamelled copper wire.
A drill bit of the desired internal diameter of the coil.
Soldering kit and solder.
Wire snips and needle nosed pliers.

For Niftymitter, use 0.75mm (or 22SWG) diameter wire, such as this from Rapid and a 5mm drill bit.

SWG/metric conversions can be found on this page.

Step 2: Turning the Wire

Using the drill bit as a template, wrap the wire, counting up to the number of desired turns. Allow 3cm of wire clear before starting the turns and keep the wire taught while turning. Kogawa has a video for this step on his site here [.wmv].

For Niftymitter, make 4 complete turns, as close together as possible.

When complete, snip off from the reel at 3cm distance from the last turn.
 

Step 3: Forming the Legs

Use some needle nosed pliers to grip the coil on the bit as shown. Bend the legs as shown so that they are parallel. Remove from the drill bit.

Step 4: Tinning the Legs

The legs of the coil require tinning to remove the enamel and prime the surface for soldering onto a board.

Use some needle nosed pliers to grip the coil while tinning - it can get very hot. Heat one leg with the soldering iron for a few seconds.

Introduce some solder to the heated leg and continue applying the iron, moving back and forth on the leg. The enamel will begin to separate from the copper and bobble.

Continue adding solder until the leg is silvered all over. You will have to turn the coil over as you do this to ensure coverage. Coax any surplus solder and enamel to the end of the leg.

Repeat the procedure for the other leg. When complete, snip of the ends of the legs, with the surplus solder attached, leaving at least 1cm of straight leg before the turns.

Step 5: Completed Coils.

Your completed coil should look like one of these. and can be inserted into a 1.5mm hole in a PCB. For Niftymitter, the transmitting frequency of the transmitter can be increased by increasing the separation of the turns of the coil. This can be achieved using the head of a small screwdriver to manipulate the gaps.

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    35 Comments

    I would like to wind a 17 micro Henry inductor. Maximum current of 30 A is epected without saturating the inductor. Which is the best way to go? Please reply

    How to I make 400micro Henry and 200 micro henry inductor plz give and in my email id knownlight@gmail.com

    user

    How to I make 8.6 micro Henry inductor plz give and in my email id
    parthkadiya772@gmail.com

    1 reply

    do you got how to make that much henery inductor? please mail me rajanchalotra23@gmail.com

    Hi! Can you help me make 400-500uH? What diameter of wire should I use and how many turns does it have? Thank you for your help!!!

    hey any one tell me the required length,diameter, of 3.2nH inductor . and tell me how can it made own

    Hi All, being brand spanking new to this, i have a question........how do you know which guage wire, and how many turns to use for a coil ?, say for eg, i want to boost 12vdc to 20vdc with a coil, trans and caps....how now do you calculate the guaging and number of turns of the wire for the coil ?

    hi, which type of wire and no. of turns is used for 0.1uH inductor for FM transmitter?

    2 replies

    use the same wire, 8 to 10 turns using a pencil

    what type of pencil ?
    moggol 2 ?

    hello, what type of wire can you suggest in making 200uH inductor for AM transmitter?

    Cheers!

    i was thinking of induction coil to heat the soldering iron point, but i am afraid it would short, is all i need a 220v diode or 2 perhaps?

    Sorry to say I'm not familiar with the types of inductor you are describing (axial lead inductors?). I suspect there is a reason for choosing one over the other, as the transmitter circuit I have worked with did specify an air core conductor.

    How can I make a 1 milihenry air core induction coil? It's for an EMF detector that I might make into an instructable.

    1 reply

    check this out
    http://www.crystalradio.net/cal/indcal2.shtml

    Hi, im working on a project at the moment and im wondering how would you go about wiring 2 coils together. One being the inductor and the other the collector. so that the electricity one flows one way. Into the collector and straight out the inductor.

    1 reply

    I'm afraid I can't help you there, not sure about that!

    How much inductance do these little guys have?

    1 reply

    we're not sure - see comments below!