inductors??

[el duderino]

Can some one please explain the whole inductor thing to me coz i going
to build a passive tone control and the parts list says i need a
5-6 H inductor i think the H stands for henry can anyone help wtih the rest............?? :shock:  :?  :shock:

[petemoore]

Can you show the schematic or provide a link?
 Sounds interesting...an inductor in a TC...I think they're talking about inductance, which is quite the equation to figure...First tack I'd take is get the actual part called for to build 'that'.
 OTOH there are TC's which can be tailored to suit, which don't call for an inductor, check at AMZ Labs Notebook!

[R.G.]

Can some one please explain the whole inductor thing to me coz i going
to build a passive tone control and the parts list says i need a
5-6 H inductor i think the H stands for henry can anyone help wtih the rest..

I'm not sure I can explain the whole thing, but I may be able to get a few pointers in.

Inductors are kind of the alternate identity of caps. Where caps block DC and conduct AC current better as signal frequency rises and work on electric fields, inductors do the reverse in all counts. They conduct DC best and conduct AC worse as frequency rises; they work on magnetic fields. They're also called chokes, as they "choke" AC conduction.

Caps and inductors work in filters by being the opposites of each other. If you put a cap and an inductor in series and then use a signal generator to see what comes through, the capacitor blocks very low frequencies, but lets more through as frequency rises. The inductor lets everything through at low frequencies, but increasingly blocks highs. So what comes through the series connection gradually increases as the cap lets more through, right up to the point that the inductor starts blocking - it's a band-pass filter, because there's a peak right where both cap and inductor are letting stuff through.

In parallel, caps and inductors form a notch filter. At low frequencies, the signal goes through the inductor. At high frequencies, through the cap. Only at frequencies where the impedance of the cap and inductor are equal does the signal get blocked.

There are many ways to connect Cs and Hs up in filters beyond these simple illustrations.

EEs have long ago decided that inductors are a bad deal. They're big and heavy for what they do, they radiate magnetic field junk, they're expensive, they're non standard. The EE biz has figured out any way it can to NOT use an inductor.

But in your passive tone control, it may work fine. Your problem is the ones I just talked about - where are you going to get a 5-6 Henry inductor. You may have looked for these and found that it's easier to get a piece of dinosaur skeleton that the right inductor.

5-6H is a big inductor. Most of the commercial ones are in the microHenry range. Your best bet is to either find a surplus pot-core inductor from old telephone equipment or to use the primary winding of a small audio transformer. The problem with this last is that even though the small audio transformers are cheap ($2-$10) they do not specify what the primary inductance is. You'll have to either measure the inductance or trust to luck.

[Hal]

continuing RG's post, you can trust your ears too.  Or make your own inductor, its _really_ easy.  Just wrap some wire around some iron.  more and tighter windings make more inductance.  

See if you can find the free download called "lessons in AC circuits."  Its part 2 of some series...you can get it legally on kazaa.  They have an excellent explanation about freqency pass fiters with caps, inductors, and both...

[el duderino]

Thanks, i dont think ill will be able to show the schematic coz it is
form Electronic Projects for Musicians and i dont have a scanner

thanks for the advise though

eamonn.

[niftydog]

in they're most basic sence, inductors oppose changes in current direction.  They do this using magnetic fields, as oppose to electrostatic charge (in caps).

They can be dangerous if not treated properly, but usually only in high energy applications.  I've seen them self-destruct whilst simply trying to do their job!

5-6H seems a huge value... sure it's not mH?

[el duderino]

im sure that this is the right value but on the schematic only half is actually conected to the board and the other side says NC.

:shock:

is this ok as i really need to find out alot more about them :lol:

eamonn

[niftydog]

so you're saying that of the two terminals of the inductor, only one is connected?

That, my friend, is a lump of useless wire.  Sure you're not missing part of the scematic?

search tpub.com for "inductors".  There's also plenty of other sites; get your google fingers limbered up!

[One-eyed Jack]

There's a guide to making your own inductors here; it's in PDF format. Hope you have Acrobat reader.

But to get several henries of inductance you're going to have to wind a very big coil...think about a coil maybe 4 feet in diameter and 4 feet high, wound with 2200 turns of wire. (Well, that would be roughly ballpark for a 4-henry air-core inductor, I think; one with a ferrite core would be a lot smaller. But still big, IMHO.)

[RickL]

Which version of EPFM do you have? In the copy I have that project uses an audio transformer like R.G. talks about and it specifies a Mouser part number. I think Small Bear offers that transformer.

Or you can buy the kit with all the parts from PAiA.

[gez]

Maplin sell little output transformers which work.  Just buy a range of caps, sling them in, listen and select the ones which work well with it.  (I just messed with this so I don't have values or anything, but they work)