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'[OT] Propic Capacitor help'
1998\07\10@112522 by Brian Gracia

picon face
Hello,

I would like to know what capacitors I should use to build the Propic.

Also, what capacitor types should be used in what applications?

Brian

1998\07\11@090417 by Octavio Nogueira

flavicon
face
To build the ProPic you will need ceramic capacitors if you mean the two on
RB6 and RB7.

Regards,

Octavio
======================================================
Octavio Nogueira  - e-mail:   spam_OUTnogueiraTakeThisOuTspammandic.com.br
http://www.geocities.com/~oct_nogueira
"ProPic" Production PIC Programmer Windows under US$20
======================================================
-----Mensagem original-----
De: Brian Gracia <.....brian_graciaKILLspamspam@spam@HOTMAIL.COM>
Para: PICLISTspamKILLspamMITVMA.MIT.EDU <.....PICLISTKILLspamspam.....MITVMA.MIT.EDU>
Data: Sexta-feira, Julho 10, 1998 12:21
Assunto: [OT] Propic Capacitor help


>Hello,
>
>I would like to know what capacitors I should use to build the Propic.
>
>Also, what capacitor types should be used in what applications?
>
>Brian
>

1998\07\13@203514 by Sean Breheny

face picon face
Hi Brian,

I can't help you specifically with the Propic, but I can give you some
general capacitor advice:

There are MANY types of capacitors, but the two most common for PIC
projects are polarized electrolytics and ceramic discs.

When reading a schematic, if you see a polarized capacitor (i.e. it has a
plus sign on it), in general, you can use a regular polarized electrolytic
capacitor (usually just called electrolytic). Jus be careful not to use a
capacitor with too low a voltage rating.

If the capacitor has no plus sign, and is 1 microfarad or lower, then
usually you would use a ceramic disc cap. If it is higher than 1 uF, you
may need to use a non-polarized electrolytic, or another type, but this
is very rare.

When designing something, you generally use electrolytics as power supply
filter caps, audio coupling caps, or (most common with PICs) rough bypass
caps (from positive supply to ground) to help supply lots of current for
a very short time when a chip suddenly changes the state of many of its
internal gates, or when it changes the state of several output lines
simultaneously.

Ceramic caps are also used as bypass caps because they have a lower ESR
(effective series resistance) so they have faster response times,
allowing them to be even more effective in the bypass role. So,
typically, you put a 10 uF or so electrolytic in your circuit for, say,
each 5 chips, and then a 0.1 uF ceramic cap across the supply pins of
each high speed chip (PIC, SRAM, etc.).

For special applications, you may need other types of caps. For example,
in a battery powered circuit, you would want low-leakage electrolyic caps
for the bypass caps, so that the leakage current doesn't dominate the
supply current drain of the device. For critical timing applications, you
would want NP0 ceramic caps, or silver mica caps, instead of the Z5U
ceramic caps you would use for bypass. These letters refer to the
temperature coefficient of the cap. NP0 stands for Negative Positive
Zero. It is very stable, meaning that its capacitance doesn't change much
with temperature.

. For very fast SRAM, you might need low-ESR
electrolytic caps to supply enough current when the SRAM's outputs are
transitioning very fast.

I hope that this helps,

Sean

On Fri, 10 Jul 1998, Brian Gracia wrote:

> Hello,
>
> I would like to know what capacitors I should use to build the Propic.
>
> Also, what capacitor types should be used in what applications?
>
> Brian
>

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