500mH coils???

[rx5]

hi all! any nice n dirty cheap trick on making one? i dont have an inductance meter that can measure that high.. only 10mH..

could someone help?

tnx

[Tychobrahe1979]

Hi rx5 have you by chance read " The Technology of the Wah Pedal " at http://geofex.com/ ? It mentions using either an audio transformer thats about $3 at Radioshack or using inductors/chokes in series to come up with the value you need. Well hope this helps.

[Hal]

make 50 10mH coils, and put them in series :-D

[rx5]

make 50 10mH coils, and put them in series :-D

r u nuts? hehehehe how about i series 500 pcs of 1mH.. makes life much easier... hehehe :lol:

[Hal]

yea, I was kidding.  There are some projects/schematics online to build inductance meters, but I think most use PICs, and are more complicated than they're worth.  Sorry I cant help you more

[rx5]

yea, I was kidding.  There are some projects/schematics online to build inductance meters, but I think most use PICs, and are more complicated than they're worth.  Sorry I cant help you more

yup.. some are PIC ....   to hard to find...

[Tychobrahe1979]

Actually if you took the time to read the article you would know with out even having to look around that Mouser carries 150mh chokes. Just for you info.

[stm]

A couple of weeks ago a circuit was posted that simulated an inductor connected on one side to Vcc.  It used one transistor, a couple of resistors and a capacitor.

There was a post about a *floating* inductor made with two op-amps and some resistors.  The good thing is that you don't have to measure, because you calculate the effective inductance upon the resistors and capacitor.

[rx5]

Actually if you took the time to read the article you would know with out even having to look around that Mouser carries 150mh chokes. Just for you info.

well i think ive read bout it... problem is MOUSER is way too far from our place... and is really a big hassle if the only thing yor about to mail order is a coil....

was only trying to find a better source..(IF) i could... ive also read bout a mouser mini transformer(audio??) that had a coil resistance of 1K w/c would be the near value of 500mH.... ive scouted lot of electronic stores in our area but all i could find are coil resistances of less than 200 ohms.... too low....

any know GOOD substitutes maybe? from broken radios or ....

tnx

[Hal]

I just saw that BG Micro sells 470 uH "RF Chokes"...39 cents each.  would these work ?

[niftydog]

BG Micro sells 470 uH "RF Chokes"

Sure, but for 500mH you'd need 1064 of them in series!

a gyrator is a possibilty. Short of that, a 500mH coil just ain't the kind of thing you find at Ratshack.

You could possibly makes some calculations for the core that you have, then "overwind" just to be safe, then make a resonant circuit, (after running some more calcs) and fine tune it to 500mH...

But it's a PITA![/quote]

[Hal]

oh wow....i feal dumb.  For some reason, I was reading mH as microhenry, not realizing that there would be an inductor as big a half a henry.  But i guess there is :-D

[niftydog]

half a henry

LOL!!! Oh man, the Henry has to be my favourite unit... that and the Siemen!

[Paul Perry (Frostwave)]

My favorite unit is the 'barn'
http://www.sizes.com/units/barn.htm
Difficult to get back on topic (almost) in one step, but, here's another 'barn': http://www.bigroadblues.com/slide/guitstuff/basics.shtml
and from a concert review a couple of years ago:
"Bo Diddley gave lots of solos, continually pressing the buttons of his specially made guitar to achieve the unusual effects."
Anyone know abt this guitar & the built-in fx (if they were?)?

[stm]

Many years ago I saw a guitar in a store that had something like 5 to 6 radio buttons in a row.  They were labeled Overdrive, Distortion, Chorus, Flanger, Delay (or something like that).  No adjustments except for the usual Tone and Volume controls on the guitar, and the pickup switch of course.

I think they were just set at some generic fixed setting.  Never came to hear it, but I guess there was a single MN3007 wired to get some chorus, flanger or slapback delay, plus an Op-Amp with a couple of diodes that you could switch in feedback or clamp mode.

Don't remind the brand of the guitar though.  I guess it may have been a nice practice instrument.  Not sure if it was a great instrument for band playing, though, since there was no flexibility to setup the controls.

[aron]

oh wow....i feal dumb.  For some reason, I was reading mH as microhenry, not realizing that there would be an inductor as big a half a henry.  But i guess there is :-D

So according to R.G., a Wah inductor could be used or 2 Radio Shack transformers in series: (This example was for 1H)

Inductors in series add. You can use two Wah inductors (usually 0.5H) or several of the more readily available 150mH inductors from Mouser. Oh, yeah, you could use two of the Radio Shack transformer primaries: see "the Technology of Wah Pedals" at GEO for the part number. They're about 0.6H I think.

[aron]

I know Torres had a midrange kit that was well received. It worked really well on my friends guitar, but on his, the inductor looked like a way inductor. Later versions used the mouser inductor, but those never sounded as good.

I wonder if we can use our Fasel  inductors in the circuit for better response.

http://www.jpbourgeois.org/guitar/micos1.htm

[niftydog]

btw, I found what I was looking for re. formulas for making your own inductors.

First, I only have info for torodal type inductors, and you must know the AL factor of the material used to make the core. It is a number than describes the inductance per turn. (this can sometimes be found, if you can find the datasheet or manufacturer of the core itself!)

Then, you run one of these equations to caluculate the number of turns required.

Ferrite materials;

N = 1000 x SQRT {L[mH]/AL(mH/1000t)}

Powdered Iron materials;

N = 100 x SQRT {L[µH]/AL(µH/100t)}

Some VHF/UHF materials specify nanohenrys per turn (nH/t).

Then, it's a matter of doing some estimating of the length of wire you need, compensating just in case you get it wrong and then working your way towards the biggest hand cramp you'll ever experience!

I did this once, and only once, to get a 55µH inductor... I'd hate to think what it would take for 500mH!!!

[David]

[Short of that, a 500mH coil just ain't the kind of thing you find at Ratshack.

Actually, they do.  At least, they did the last time I looked.  IIRC, this is the exact transformer that R.G. mentioned as being a possibility for a wah inductor.  It also comes in handy for a Bobtavia or a Smalley Simple Octave Up.