Some sort of inductive decoupling on the DC?

On 1/30/06, Crist=F3v=E3o Dalla Costa <cdallacosta@gmail.com> wrote:
>
> I've just had a quick power shortage at my house... Ligthning, then the
> lights went off for a second and back on again. Only problem is the
> PIC18F4525 I was working with is no more. ICD2 reports its device id as
> 00,
> I can program it but it fails. Other chips in the board, including CMOS
> logic, CMOS op amps and a VFD display were not harmed.
>
> That's actually the second pic I have that burned in this fashion, the
> first
> went away when a short circuit in the AC part of the circuit board
> presumably caused a power surge. And again the PIC was the only component
> to
> fail. A previous board version had problems with relay switching resetting
> the pic.
>
> Now, these are hand built prototype boards for a product I expect to have
> ready in a month or so. It's a low volume production (20 units per year or
> so) but a quite expensive product and it would look bad if customers had
> to
> replace control units every couple months... This is actually my first pic
> product so I figure I'm missing something here.
>
> The power supply consists of a transformer, full wave rectifier with
> 1000uF
> electrolytic, a 7805, another 1000uF electrolytic with a 100n disc cap,
> and
> every digital chip has its own 100n disc cap. Board current comsumption is
> in the 400mA range. Would a series inductor help with the problem? What
> else
> can I do to make my project surge-proof?
>
> Thanks in advance.
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