Solon Caceres Moreno wrote:
>
> Engineers:
>
> For a project based on PIC, How it can be feed from a source of 110 V AC 60
> Hz without using a transformer?

There are several ways for doing this, the easiest involves using a
single-wave
rectifier in series with a resistor to charge up an electrolytic
capacitor.  A
zener diode parallel to the capacitor limits the output voltage to some
sensible
level.  Caveats: the resistor dissipates lots and lots of energy (to
give 50mA at 5V the resistor will dissipate 50mA*105V=5.3W) and the
output voltage will have a very noticable ripple.  To improve on the
ripple, replace the 5.1V zener with an 8V2 zener, and use a 78L05 to
regulate down to 5V.  Of course, your circuit may work reasonably well
without removing all the ripple.

              R
  AC in ---\/\/\/---->|----+---+------- DC out
                           |+  | +
                          ===  ZD 5V1
                           |   |
 AC rtn -------------------+---+------- DC return

The second solution involves using one of the integrated
line-AC-to-5V-DC circuits -- these are available and require even fewer
components and will give you far less headaches.  These work by
switching the AC line to a holding capacitor whenever the AC line
voltage is less than a set voltage, and regulating the switch so that
the output voltage is close to 5V.  Someone on the list will remember a
part number, I'm sure :-)

Frank
------------------------------------------------------------------------
Frank A. Vorstenbosch     <SPAM_ACCEPT="NONE">    Phone: 0181 - 636 3000
Electronics and Software Engineer                 Mobile: 0976 - 430 569
Eidos Technologies Ltd., Wimbledon, London        Email: fav@eidos.co.uk