# Inductor coil

1. Mar 6, 2013

### prernakabtiyal

i have to make a 10mH inductor coil for an LCR resonant circuit.could someone please guide me
on which gauge of wire to use and how to wind it to make a coil within 5% variation? i need the coil to be close enough to 10 mH for resonance.

looking forward to ur help...

2. Mar 7, 2013

### marcusl

Just google inductance formula and you'll find plenty of references. Here's an online calculator
http://www.m0ukd.com/Calculators/air_core_inductor_calculator/
I don't know if you'll get 5% accuracy. Make sure you account for the dimensions of insulation on the wire and keep in mind that, in general, the formulas should be more accurate for long coils (length/diameter > 5). Keep frequency low, because inter-turn capacitance becomes important at high frequencies causing the effective inductance to drop. Ham radio sites should be helpful in that regard.

3. Mar 7, 2013

### sophiecentaur

Because of the self-capacitance, mentioned above, you may need to tune your final circuit with a variable C. There is a lot of black art in RF inductor winding. If you make them too physically big then the connecting leads become relevant. If you make them too small, the self-capacitance gets significant.
Don't give up if the first few don't do exactly what you wanted.

4. Mar 7, 2013

### Carl Pugh

It's not that easy to design and build an inductor.
Why don't you just purchase an inductor? Google 10 mh inductor.
If you build the inductor, you will probably need a core. Type of core depends on the operating frequency.
Any reasonable size copper wire can be used. Wire diameter should not exceed about twice the skin depth at the frequency that inductor is operating at. Inductor loss will depend on the wire size used. Smaller wire size, the higher the loss and the lower Q of the circuit.

If you explain what you are trying to do, someone may be able to suggest an easier way to accomplish your objective.