Decoupling Capacitors: 22uf instead of 10uf

Other Hardware General Electronics
1

Hi, I am building my first "arduino on pcb" following some schema found on internet.
Can I use 22uF electrolitic capacitors for decoupling in\out 5V voltage regulator (instead of the 10uF caps)?
Is it important the 10uF value or anything "near" can be ok?
Thanks

2

xxxzanka:
Hi, I am building my first "arduino on pcb" following some schema found on internet.
Can I use 22uF electrolitic capacitors for decoupling in\out 5V voltage regulator (instead of the 10uF caps)?
Is it important the 10uF value or anything "near" can be ok?

If it's bigger, it's OK (without going crazy).

Much more important is to use the correct types.

3

22uF should be fine.

Most cheap capacitors are only ball-park figures anyway, and their actual capacitance will change drastically as temperature and current changes.

4

A larger value should work fine, although some LDO and surface-mount v.regs
may suggest specific types and values for the filter caps. Also you still need
a 100nF cap in parallel with the larger one. They filter noise in different
frequency ranges.

5

Thanks for the extra 100nF cap suggestion: should it be polarized or it doesn't matter?

6

xxxzanka:
should it be polarized or it doesn't matter?

Non-polarised ceramics will be fine (marked 104). Buy many as you'll use them frequently.

Cheers ! Geoff

7

As Geoff said, ceramic, marked as 104, and the tolerance is not important.
Most controller boards will have 4 or 6 of these scattered about the board,
on v.reg outputs, at Vcc pins of chips, etc.

8

I've been using these polyester caps for decoupling (got a bunch of 100nF caps from somewhere):

Are they better or worse than ceramic capacitors?

9

I can't say definitively, but the page linked indicates usable for bypass and decoupling.
I use Metallized Polyester and Polypropylene caps for bypassing the motor power
busses on all of my motor controllers, as they tend to deal with higher voltages
and are "self healing". You also see them used in snubbers on relay contacts. They
do tend to be larger and more expensive than the small ceramics.

10

ph77:
I've been using these polyester caps for decoupling (got a bunch of 100nF caps from somewhere):
Film capacitors Made in Germany. - WIMA – Competence in Capacitors

Are they better or worse than ceramic capacitors?

They may not actually be decoupling - decoupling caps must be low inductance to function properly.
Ceramics are inherently low inductance, for poly film it depends how they are wound. There should be
at least one ceramic decoupler next to each chip, not somewhere else on the board, note.

11

ph77:
I've been using these polyester caps for decoupling (got a bunch of 100nF caps from somewhere):
Are they better or worse than ceramic capacitors?

The answer is, it depends. Their capacitance is more stable than non-C0G ceramics. You also can get relatively high capacitance for a given volume at high voltage. So these make them "better."

However, their impedance tends to be higher, so their effective frequency range is lower. They also cost more and almost always have high lead times. These makes them "worse."

Generally film caps are used when the voltages are too high for ceramics to have usable capacitance.

oric_dan:
I can't say definitively, but the page linked indicates usable for bypass and decoupling.

Here's a secret from the capacitor industry: we say that on every capacitor catalog regardless of the style. :wink: Over 85% of capacitors sold are used in "decoupling" applications.

12

[quote author=James C4S link=topic=172875.msg1286137#msg1286137 date=1371755138]

oric_dan:
I can't say definitively, but the page linked indicates usable for bypass and decoupling.

Here's a secret from the capacitor industry: we say that on every capacitor catalog regardless of the style. :wink: Over 85% of capacitors sold are used in "decoupling" applications.[/quote]
LOL.

13

Thank you for the helpful answers, guys!