How can I test inductor values? Know the values in Kodak MAX disposable?

[**DONOTDELETE**]

I'm planning on building a dc-dc converter to drive an LS or white 5mm array. I need an inductor for the circuits I'm looking. I've gutted some disposable cameras which have small inductors on them for the step up for the flash, and have a few others laying around.

All I have right now is a DMM, and a 13.8v power supply and was wondering if there's a way I can test the inductance values of these inductors. I don't mind building circuits and measuring stuff. I have a basic ac/dc electronics knowledge, and a little solid state understanding (diodes, transistors).
If anyone knows the values in Kodac MAx, or other disposable cameras, that info would be helpful also.
thanks,
-Jake-

 

[Silviron]

I'm no expert on inductors, but if they have any vari-colored stripes on them, you can figure the values from that.

I don't have a color chart handy, but I'm sure a quick search of the web would turn one up.

 

[remuen]

Jakester
There is absolutly no way to asses the inductance value only with a DMM and a power supply.

 

[jeff1500]

Maybe build a circuit, then try different inductors to see how much difference there is in output current and efficiency. That you could do with a dmm.

Someone I was talking to said he once made an inductor out of a pencil with wire wrapped around it. Maybe try a big carpenter's pencil.

You could use your standard circuit (like a two transistor step-up circuit) to make your own inductor correlation. Maybe name it after yourself. For example, an inductor of 1.0 "your name here" will cause a flow of 20 mA in one led with 2AA batteries in your standard circuit.

And oh, by the way, that's a good idea to look inside old disposable cameras for parts. I'm going to look around for one.

 

[Evan]

I doubt the inductors in disposable cameras will be much help driving LEDs; the circuit in the camera is made to produce a very high voltage at a low current that charges the capacitor which stores knock-you-on-your-butt, maybe deadly, power. So they are probably many millihenries but with a DC resistance so high they'd be useless for LED work. Cores might be useable to wind your own.

MrAl gave a method to measure inductance based on measuring the ratio of the impedance to a resistor in series with it on an AC source. Somewhere in that long Zetex ZXSC300 single-cell LED driver thread (sumarized at Duggg's Summary). He computed some values to check a coil. You should be able to do a variation using 60Hz from the mains (probably best with a transformer), impedence=2*pi*frequency*inductance, and an "appropriate" resistor. I couldn't find the right page on a quick look, but if you are going to do DC-DC converters, I highly recommend the whole thread.

Or, while you are buying restors to use in the above scheme, visit BG Micro where a whole range of inductors from .12 uH to 3300 uH are available at 4 for $1.

But if you really get into DC-DC converters, you'll probably want to wind your own inductors to get a low DCR. So you might want to visit CS Sales where they have the LCR1810 for $90 which will measure inductance from 200 uH with resolution of .1uH thru 20H, just the thing to find out what you've made after you put 10 turns on some unknown ferrite.