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FrozenGate by Avery

Inductor help please

AUTO XX

AUTO XX

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Aug 13, 2010
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I bought a few inductors on fleabay a while back, they are rated @ 1A apiece but the price was right so I got them anyway.
I need 3-6A and the guy that I bought them from was either trolling or there was something lost in translation.

My question was is there any way to wire these inductors (parallel or series) to get them to handle the required current?
His response:
"The inductor is 1Amp.

Parallel inductance
A fully coupled: inductance unchanged
No coupling: inductance * 0.5"

Well, he might as well have been speaking martian so I started learning but I must be more dense than previously though because I can't seem to find any relevant equations or information.

I then basically asked him how to "fully couple" inductors and his response was:
"Hi,This item is +/- 10%.
For example:221uH and 221uH ,full coupled.
For example:221uH and 222uH ,No coupling.
Thanks

o.O

Now my head hurts :(

These little inductors have
69 wraps of .54mm wire
the toroid is
~13.5mm diameter (not including wire)
~4mm thick
Can I wire the inductors together in any way to keep the inductance unchanged and just let it handle more current?

I have another larger toroid (scavenged from something a long time ago)
it has 74 wraps of .8mm wire (should handle at least 6A I think)
20.3mm diameter toroid (not including wire)
6.48mm thick
I don't know the inductance of this toroid though, I can unwrap a bit if needed but it might not be at all suitable.

I would prefer to keep my board a little smaller and just use the bigger inductor (instead of 5 little ones) but they work out a lot more spendy than the little guys.
I'll also be making more than one if I can get the price down a bit by wrapping my own inductors
These are for desluphator circuits, need 220uH, and if you need any more info I'll try my best to get it.
Thanks for the help guys, I'm at a loss on this part of the project....:beer:

I'll add info if I think of anything else as well ^_^
 





They are similar to resistors with respect to series/parallel arrangements.
A 3x3 series-parallel grid (totaling 9) will give you the same inductance but with a 3A current rating.
A 6x6 series-parallel grid (totaling 36 :p) will give you the same inductance but with a 6A current rating.
3 in parallel will give you a 3A current rating, but at a third the inductance of a single component.
 
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From what I can gather there are generally no markings on it apart from sometimes it will have a single wrap of plastic around the circumference with the code on it.
The inductance depends on diameter of the toroid, composition, (ferrite, iron powder, etc.), the number of wraps, the width, the inner diameter, I think even the gauge of wire you use makes a difference.... O.O
Thanks for the info about the similarity to resistors Cyparagon, if I can't get premade inductors the value I need, I'll just order a bunch more of these little guys.
I think a good quality DMM that can measure inductance as well as capacitance might be a good investment at this point, especially if I intend to wrap my own inductors ;)
Cores seem pretty inexpensive and enamel wire is easy enough to get so that might be the most cost effective solution.
I always like good tools ^_^
 
Most DMM's don't measure inductance. Some cheap china meters made for measuring resistance, capacitance and inductance can do it, but those have limited resolution (1uH). A good LCR meter will be very expensive but probably not needed. Making your own inductors is not that hard, so you can consider it as an option.
 
Ideally I would like to make my own inductors but how am I to know the inductance if I have no meter?
Is there a table somewhere that has the values X inductance?
Or is there an equation that I can use?
I know for ~6A I will need at least 18AWG wire and the toroid will have to be at least an inch in diameter (even just logistically to wrap enough wire on) but thats about all I know.
 
The ARRL Handbook (Big edition) has , under basic electronics and antenna design, Amidon ferrite and its properties. (Look under "traps".) It shows how to wind a certain inductance toroid.

Now, note that you have to Know what type of composition the ferrite Is to do this! You can also use a grid dip meter and known capacitance (silver mica cap) to find resonant frequency, then substitute into the equation to have it come out in uH. You need to leave a large loop of wire between the cap and toroid so the GDO's probe will get in there or it won't read---toroids do this, Again, the handbook shows all.

Or, you can do what I did and wind 10 turns, say, of #18 wire (good for 3 amps), and take it to a real electronics store that sells good Fluke induction meters. Ask to be shown L-meters, ask for a demo on your toroid. They'll be glad to show you how a $250-to-$1000 instrument works, if you act like you are willing to buy one/several.;)

You can write down the inductance per 10 turns, and go from there.

EDIT: Spelin errrs.
 
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In theory you could subject your coil to 60HZ AC at low voltage from a transformer*, measure the current and then calculate the inductance. (there are likely something on Wiki on inductance/capacitance.

*or a cascade of two 110V-12V getting you down to 1.3V or so.
 
ninefingers said:
The ARRL Handbook (Big edition) has , under basic electronics and antenna design, Amidon ferrite and its properties. Llook under "traps".) It shows how to wind a certain inductance toroid.

Now, note that you have to Know what type of composition the ferrite Is to do this! You can also use a grid dip meter and known capacitance (silver mica cap) to find resonant frequency, then substitute into the equation to have it come out in uH. You need to leave a large loop of wire between the cap and toroid so the GDO's probe will get in there or it won't read---toroids do this, Again, the handbook shows all.

Or, you can do what I did and wind 10 turns, say, of #18 wire (good for 3 amps), and take it to a real electronics store that sells good Fluke induction meters. Ask to be shown L-meters, ask for a demo on your toroid. They'll be glad to show you how a $250-to-$100 instrument works, if you act like you are willing to buy one/several.;)

You can write down the inductance per 10 turns, and go from there.
Click to expand...

Well, you deserve your first +rep my friend.
Just gave me about 4 avenues of learning to explore ^_^
I'll likely get an induction meter in the future, I like to stay in the next lower tax bracket by buying lots and lots of tools (best investment there is ;) )
Also, if I'm buying cores from a reputable dealer, I'll know the composition anyway.
Thanks again for the info ninefingers (I'm 8 and 1/2 fingers ^_^ ) And welcome to LPF!
 
AUTO XX said:
Also, if I'm buying cores from a reputable dealer, I'll know the composition anyway.
Click to expand...

This is True. But, if you deal with surplus/buy at swaps like I do, you probably won't know what core you have. I've always wanted to find a cheap source for Variac cores to wind my own high-efficiency. low-turn, extremely- light line transformers. The turns ratio is about 1.25-to-1.5 turns per volt!:D

In theory you could subject your coil to 60HZ AC at low voltage from a transformer*, measure the current and then calculate the inductance. (there are likely something on Wiki on inductance/capacitance.
Click to expand...

It depends a lot on frequency, too. I don't know what freq he is using. I know the ferrite cores from old fly backs are efficient at 15 Kc. The turns ratio for them at this freq, is again about 1.5 turns/volt. I don't think this stuff will work at all on 50/60 cycle.
 
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You're thinking of reactance. Inductance is constant, regardless of frequency.
 
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