On 9/5/05, Daniel Chia <danielcjh@yahoo.com.sg> wrote:
> Hi,
> 	First off, think I wasn't very clear in my post, but my motors
> run off the unregulated side of the power supply. The regulated side is
> for digital circuitry and such.
> 
> 	Right now what I'm gathering is that the tant prolly isn't up to
> the task of regulating the battery supply. Instead I probably could
> consider a solid aluminium electrolyte. However I think that for the 5V
> regulated side a 16V tant should do the job pretty well.
> 
> 	Thoughts anyone?


  You are asking questions without answering. I'm asking you twice:
Do you have suppressor diodes on the H bridge ? 
If yes, there are connected in one point on the Vcc and on the GND ? 
If no, then connect those 4 schottky diodes
If you have diodes, do you have a capacitor of about 100...470uF
between that two points and no other place ?
If yes then your capacitor is a small SMD tantal one ?
Does it hot ? 
If yes:
1. change it with an aluminium one, not necessary solid aluminium
2. use a D size SMD tantalum 100-150uF in parallel with a 33-100nF ceramic X7R

No more to say on this problem. Solved.

Vasile 


> 
> ------------------------------------------------------------------------
> Daniel Chia
> 
> "Genius is one percent inspiration and ninety-nine percent
> perspiration."
> 
>      - Thomas Edison
> 
> E-mail: danielcjh@yahoo.com.sg
> MSN: danstryder01@yahoo.com.sg
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> ------------------------------------------------------------------------
> 
> 
> > -----Original Message-----
> > From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On
> Behalf Of
> > Russell McMahon
> > Sent: 05 September 2005 04:33
> > To: Microcontroller discussion list - Public.
> > Subject: Re: [EE]: Tantalums cap for power supply regulation
> > 
> > > Generally, tantalums are most *un* suitable for power supply
> > > applications.
> > > They are quite prone to failure, sometimes in spectacular fashion. A
> > > low-Z aluminum is a much safer bet.
> > >
> > > If you *must* use them, then heavily derate the voltage (use a
> > > capacitor
> > > rated for 3 times as high as the working voltage), and follow all
> > > data
> > > book recommendations to the letter.
> > 
> > Yes. This is a warning which must be noted. Tantalum capacitors are
> > superb when they work. They offer very high capacitance per size and
> > excellent ESR. But in an amateur or experimental situation where
> > conditions are not well behaved or well known they can fail
> > catastrophically.
> > 
> > A tantalum cap that experiences a voltage spike higher than its rated
> > voltage, even a very brief one, will often fail very spectacularly.
> > They often smell bad, make interesting sounds, smoke, catch fire or
> > explode in various combinations. I've seen  one do all of these in
> > that order :-).
> > 
> > Manufacturers spec sheets often specify minimum supply impedances they
> > should be used with and even suggest adding some ohms of resistance in
> > series.
> > 
> > A **solid** aluminium capacitor has the advantages of tantalum without
> > the catastrophic failure mode.
> > 
> > 
> > 
> >             Russell McMahon
> > 
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