Hi, this may seem like a dumb question but are you saying the one cap
have to be connected to power and the other one to ground or actually
one capacitor connected between power and ground?  Sorry..




On Sat, 11 Sep 2004 11:17:26 +0100 (BST), Howard Winter
<hdrw@h2org.demon.co.uk> wrote:
> Joe,
> 
> On Sat, 4 Sep 2004 21:19:48 -0400, Joe Jansen wrote:
> 
> > Also will be adding the cap on the power / gnd.  Shoudn't be an issue
> > in this case, since I have the power supply with a big filter cap, but
> > one never knows.
> 
> Well actually there are basically two reasons for capacitors across power supply lines - the one you have
> deals with one, which leaves the other!  :-)
> 
> A "big filter cap" looks after things coming in from outside, and helps to smooth out dips in the supply
> voltage due to varying loads in your circuit, but it tends to be some way from the processor (generally next
> to the voltage regulator) and is usually an electrolytic of a good number of uF.
> 
> The other thing that needs doing is "decoupling", which is to "short out" noise generated by the processor
> itself, and that needs to be close to the processor (ideally soldered direct to the pins of the processor
> itself but this is rarely practical) and is typically a 0.1uF ceramic.  Without this all sorts of strange
> things can happen, which is why Bob (I think) suggested it.  They used to make IC sockets that had decoupling
> caps built-in across the power supply pins, but these seem to have disappeared and wouldn't have had the right
> pins connected for a PIC anyway, but they were a Good Thing!
> 
> Now some purists may disgree completely with my description above, in that it may be over-simplistic (or
> perhaps actually wrong!), but it works for me and I like simple explanations where they work!  :-)
> 
> Cheers,
> 
> 
> Howard Winter
> St.Albans, England
> 
> 
> 
> 
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