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Unread 02-27-2002, 05:16 PM   #1
Jim
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A little help. Is a "Radial" Capacitor the same as a "Polarized" Capacitor?

I decided to build a single LM350T voltage regulator for my dual 120MM Panaflo's but I cannot locate a "polarized" 1 MF capacitor.

I have performed numerous searches on several electronics parts seller sites with no success.

Need your help on this.

Jim
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Unread 02-27-2002, 07:20 PM   #2
Mr Evil
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'Polarized' means that you can only apply a DC voltage in one direction - the other direction will make it start outgassing (i.e it will die). Almost all electrolytic capacitors and tantalum capacitors are polarized. Make sure you observe the polarity when using them (they will be marked with a + for the positive terminal).

'Radial' and 'axial' refers to the way the leads are attached. Axial leads are one at each end, and radial is both at one end. This has nothing to do with whether or not it is polarized.
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Unread 02-27-2002, 09:03 PM   #3
Jim
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MrEvil-

Thanks for the info. Now if I could just locate a polarized 1 uf capacitor for this project.

Jim
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Unread 02-27-2002, 09:55 PM   #4
DigitalChaos
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you dont need the exact caps for that... just get somethin atleast those sizes. the caps just smooth out the voltage. bigger caps = more potential smoothing
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Unread 02-27-2002, 10:08 PM   #5
Jim
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Digital-

Hear me out. I am not very knowledgeable about the various descriptions used to specify some of these parts.

Yes, I know what a capacitor, resistor, potentiometer is etc. but the variety is not my best subject. The building of this regulator calls for a polarized cap, and I just would rather not mess up. If I knew all the ins and outs I could substitute, but I just don't. Now if we were talking about substituting a circuit breaker or a motor starter for you house or factory I can improvise in a second. But in this case I am a little confused.

Heck Radio Shack didn't even have one, maybe a different store?



Jim
Go here to see what I want to build using the LM 350, for greater capacity.
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Unread 02-27-2002, 10:21 PM   #6
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You should be able to use any type of capacitor in place of C2 in that circuit, as long as it is at least 1uF and rated for more than the maximum output voltage you will use. The main reason to favour polarized types (electrolytic and tantalum) is that they are smaller and cheaper for the same size and voltage rating compared to other types.
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Unread 02-28-2002, 07:22 AM   #7
Jim
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Mr Evil-

OK, thanks for that.

If I substitute the cap, how can I be sure which is the positive lead on the capacitor I use? Heck I don't care if I spend a little more, the whole thing together shouldn't cost more than $15.00 or so.

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Unread 02-28-2002, 07:38 AM   #8
Mr Evil
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One of the leads will be clearly marked. Either the negative one will be marked with a '-', or the positive one with a '+'. It should be fairly obvious.
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Unread 02-28-2002, 09:33 AM   #9
Jim
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Mr. Evil-

That explains it then, I thought it was only the polarized caps that were polarity identified.

Thank you!
Jim
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Unread 02-28-2002, 11:06 AM   #10
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Sorry, I think I misunderstood: Only polarized capacitors have the polarity marked.
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Unread 02-28-2002, 11:13 AM   #11
futRtrubL
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Only polarized caps need the polarity marked, non polarized caps can be put in either way around.

Edward
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Unread 02-28-2002, 03:55 PM   #12
Jim
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futRtrubL-

Why does this item require a polarized cap then?

See link I posted above for schematic if needed.

Jim
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Unread 02-28-2002, 11:47 PM   #13
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As Mr. Evil said "The main reason to favour polarized types (electrolytic and tantalum) is that they are smaller and cheaper for the same size and voltage rating compared to other types."

Edward
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Unread 04-06-2002, 08:15 PM   #14
Brians256
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If I'm not mistaken, tantalum caps are faster response than electrolytic capacitors. Also, polarized capacitors are said to be faster response than non-polarized electrolytics.

I don't know whether that is true... but that is what I remember someone saying in a thread about adding capacitors to a mobo (to smooth out the power given to the CPU).

Take that with a grain of salt.

With the circuit you are talking about, I feel confident in saying: use the cheapest capacitor you can find that meets the 1uF spec. You might want to use a 35V capacitor just to make sure that it can stand up to feedback from the fan, though.
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Unread 04-07-2002, 08:57 AM   #15
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Thanks Brian
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