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'22uH Power Inductor' doesn't look the the same...

by kloan on Sun Sep 03, 2006 5:51 pm

I picked up a 22uH power inductor, as listed in the parts list.. and it looks more like a resistor than what the one in the pic looks like. What exactly is that part? I asked the guy in the shop and he pretty much didn't understand why it was being used in the first place... so no help there. I also got a 22mH which looked similar to the one in the pic, but I'm not going to use either one until I know if it'll work.

Someone please help.. I'd like to finish this up..
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by hal90002010 on Sun Sep 03, 2006 7:03 pm

A very large resister perhaps?


The value is much more important than the way it looks.

How do you intend to mount it.
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by kloan on Sun Sep 03, 2006 7:34 pm

It's the same size as a normal resistor.

I was just going to solder it where it's supposed to go. There isn't a polarity marking, so I guess it just goes in there... but I'm really confused as to why the one in the pic looks so much different than what I got. Just want to be sure what I have will still work.. don't want to fry anything.
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by miguel_angelo on Sun Sep 03, 2006 8:24 pm

The one that comes with the kit now and is pictured in the instructions has an ferrite core and both wires on the same side of the part. The first prototype made by LA used a different inductor that was mounted on top and across the IC and it did resemble a large black resistor - it also had a ferrite core.

There are also inductors with a air core (nothing in the middle of the coil). Variable inductors use a movable ferrite core that moves up and down inside the core varying the inductance of the part.

Some times, in some DIY projects, you also find instructions to create your inductor by wrapping very fine enamel copper wire around a resistor, soldering each end of the wire to each side of the resistor - making it a carbon core inductor.

The easiest for you would be to try the circuit on a prototype board first and compare the behavior of the mintyboost with the two different inductors you have.

Posting a picture of the part (placing the picture somewhere in the internet and adding the link to a reply) would also allow others to maybe recognize it.
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by kloan on Sun Sep 03, 2006 8:40 pm

Here's a pic. I swear they put these in the wrong bin. It's actually closer to an 'aqua' colour, if that makes any difference...

Image
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by hal90002010 on Sun Sep 03, 2006 9:46 pm

What is its resistance.

Looks like a 22 uH coil to me.

I do not think it is rated at 1.2 amps though.
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by kloan on Mon Sep 04, 2006 12:09 am

Unfortunately, I don't know the resistance. All the bin label said was 22uH, that's it.

Should I just go ahead and use it, and see what readings I get from the multimeter?
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by miguel_angelo on Mon Sep 04, 2006 12:16 am

Here you can see a color table (same coding as resistors) for inductors:

http://www.elexp.com/t_induct.htm

Current rating as Hal pointed out maybe the issue here. By the size of it (it seems to be size of 1/4W resistor from the picture), it is probably not rated for 1.2A as required to be used by the MAX756 IC.

On this page of the Digikey US catalog you can see similar inductors to yours and their dimensions. The rating is indeed much lower at 190mA.

http://dkc3.digikey.com/PDF/T062/1042.pdf

On the paper Digikey catalog (Hong Kong version 051), I found some more inductors similar in size to yours and they are all rated at 144 mA to 295 mA.

All axial inductors rated for more than 1.0A seem to be at least 10 mm in diameter.
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by kloan on Mon Sep 04, 2006 2:06 am

Ah, ok I see. Thanks for the replies guys. It's definitely too small then for this use. I guess I'll just try to get some samples ordered, or just order it from Digikey... dang, I was hoping to get this thing finished this weekend.
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by adafruit on Thu Sep 07, 2006 3:12 pm

thats an inductor, but its a very low power one. it certainly wont be able to carry the power necessary for the mintyboost to function properly. you want a 1Amp+ power inductor!
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Thanks & a question

by evo_lution on Tue Sep 12, 2006 4:29 am

Firstly thanks for the excellent MintyBoost, i built mine point-point and it works great.
My question is the 22uh inductor i ordered looks like the one above,( i need an axial vers 'cos i built the single layer prototype) what will the downside be: overheating if charging my iPod for a long period/more serious? fire risk?

thanks :)
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by adafruit on Tue Sep 12, 2006 2:30 pm

worst thing could happen is it catches on fire from overheating
i dont think it could damage your ipod... but thats not a guarantee
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by evo_lution on Wed Sep 13, 2006 4:01 am

Thanks for the quick reply.

evo
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by GrinningArmor on Thu Mar 22, 2007 7:03 am

I got one of these too, but I believe mine's quite bigger (the actual "body" of the part, without the leads, is just a little over 1/4 of an inch long, and the thickest part is exactly 1/8 of an inch wide). Could it work? How do I know if it's rated at 1.2A?
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by adafruit on Thu Mar 22, 2007 12:50 pm

it is definately not a power inductor
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