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Author Topic: using smd cap istead electrolit  (Read 1682 times)
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alberto110
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« on: January 21, 2012, 05:35:11 17:35 »

can i use smd capacitor in max232 istead electrolit cap ?
ofcoure  in crystal  atached to microcontroler , is it possible to use smd cap .
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gan_canny
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« Reply #1 on: January 21, 2012, 06:19:42 18:19 »

Yes but still watch the polarity
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solutions
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« Reply #2 on: January 22, 2012, 01:57:42 01:57 »

Yes but still watch the polarity
There is no polarity on an SMD ceramic cap.

If your wallet can take being emptied (ceramics are a lot more expensive per uF), yes you can replace an electrolytic for the same voltage and value for a MAX232 app.

For the crystal, you SHOULD, but watch your pad sizes.
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bigtoy
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« Reply #3 on: January 22, 2012, 05:04:17 05:04 »

On the MAX232 and its relatives, SMT caps are the only caps I use. In general those small value caps are not polarised (check the datasheet - I once saw one that was polarised, but the vast majority are not). Aside from the obvious space saving, I personally find the SMT parts quicker / easier to solder as well. It's all good.
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StackPointer
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« Reply #4 on: January 22, 2012, 11:34:57 11:34 »

MAX3232 is by far best replacement for MAX232. It requires only 100nF for level shifting, so ceramic capacitors can be used without problem. And besides all that it runs from 3 to 5V.
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gan_canny
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« Reply #5 on: January 22, 2012, 02:10:44 14:10 »

Well,
      SMD caps can be polarized...it is true ceramics aren't...never the less checking for polarity markings is useful if only to be assured the cap is non polarized...and yes there are surface mount electrolytics and tanatalums that are polarized.
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solutions
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« Reply #6 on: January 23, 2012, 06:58:01 06:58 »

Your prior posting was not in the context of what was posed by the OP, mine was.

It's Ok to get corrected here - this isn't school where you get a D- for your reading comprehension skills and for having the poor guy pull his hair out looking for polarity on a ceramic when there isn't one. Part of the learning process is...learning, not grades.  No need for subsequent noise to state the obvious, save face, or belittle a poster with dozens of years in electronics and who provided the answer to the posed question.

"istead electrolit cap ? "

AND

" in crystal  atached to microcontroler , is it possible to use smd cap"

I want to learn how you use expensive and unreliable tantalums (or "electrolytics") for pulling a microcontroller crystal since you seem to imply with your second post that you can.

meanwhile, from http://en.wikipedia.org/wiki/Tantalum_capacitor

"The tantalum capacitor is a highly reliable type of electrolytic capacitor,"
« Last Edit: January 23, 2012, 07:05:32 07:05 by solutions » Logged
SpaleKG
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« Reply #7 on: January 23, 2012, 09:43:24 09:43 »

There is no polarity on an SMD ceramic cap.

If your wallet can take being emptied (ceramics are a lot more expensive per uF), yes you can replace an electrolytic for the same voltage and value for a MAX232 app.

For the crystal, you SHOULD, but watch your pad sizes.

@solutions: The question have 2 parts.

@alberto110: your answers.
1st is about electrolyte in max232. So answer is yes, because there are existing SMD version of them (still take care about voltage and polarity).

2nd is about capacitors for quartz. They are ceramics and also yes, they existing in SMD version. Bottom line you can use SMD version.
« Last Edit: January 23, 2012, 09:45:42 09:45 by SpaleKG » Logged
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