Author Topic: Capacitor question ...............  (Read 257 times)

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carlso

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Capacitor question ...............
« on: March 07, 2021, 09:58:29 PM »
-1

I need to show my ignorance and ask for some guidance.
I have purchased two different caps from Digi-Key and am not sure why nor which ones would be best to use. So would somebody please set me straight.

package #1


package #2


I probably should have ordered 220uf but I didn't. The AVX has 10% on it but the Panasonic does not. Either one of these be OK to use?

Thanks for your help.
Be well,
Carl
Carl Sowell
El Paso, Texas
Southern New Mexico N Scalers, Las Cruces, New Mexico

reinhardtjh

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Re: Capacitor question ...............
« Reply #1 on: March 07, 2021, 10:30:21 PM »
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The Panasonic are Poly Tantalum caps which have a somewhat better voltage tolerance.  The rule of thumb for typical tantalum caps is you only want to approach about 50-60% of their rated voltage, in this case 20V which would be 10-12V.  Whereas the Poly Tantalum caps the rule is about 80% which would be around 17-18V.  That's just one of those guidelines.  People exceed them most of the time with no ill effect, but cautious designers/users try to follow them. 

Use the Poly Tantalums first.  Then either get more or decide about taking the risk (of a small explosion/fire in your loco) with the regular ones.
John H. Reinhardt
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C&O HS #11530
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Steveruger45

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Re: Capacitor question ...............
« Reply #2 on: March 07, 2021, 10:55:18 PM »
0
Carl,
I would use the poly tantalums in preference for reasons as mentioned by John’s post.
I have used tantalum caps but have now gotten rid of them.
« Last Edit: March 07, 2021, 11:01:03 PM by Steveruger45 »
Steve
Atascocita, Texas

carlso

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Re: Capacitor question ...............
« Reply #3 on: March 07, 2021, 11:14:53 PM »
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Thank you John and Steve. Now I remember buying the "poly" caps for the very reason you guys mentioned. Must be my age as I looked at both of these packages and absolutely missed the "poly" tag. Boy it is heck to be "slower". I shall use the poly caps. I have some 220uf 16v that will go out along with the plain tantalums.

Thanks again, great help,
Carl
Carl Sowell
El Paso, Texas
Southern New Mexico N Scalers, Las Cruces, New Mexico