Study switching power supplies.  If you only need 5 volts, use a transformer
rated for, let's say 24 VAC at 240 in.  At 120 in you'll get 12vac, and there
are many switchers available with an output of 5v and input ranging from 8-30
volts.  Or, go to Radio Shack and get their power supply book, which gives
enough info to design and build your own switchers (plus the obligatory linear
regulators).  (Sorry to those international members of the PICList, I do not
know of a similar resource for a good power supply book)

-Adam

John Perkinton wrote:
>
> I need a space saving power supply for powering a pic chip and very little
> other components from the mains directly which will work in any country.
> I've been looking at the Harris Semiconductor HV-2405E which RS Components
> can supply, but due to the size on inline power resistor (5W) the heat
> disapation is very high, no use for plastic enclosures. Has anyone any other
> ideas, or should I just use a 240V-12V transormer, a bridge rectifier, a 35V
> 470uF cap, and a 7805. This seems to work well on both 240V and 110V, but is
> rather large, or does anyone know of a supplier of ultra small transformers.