Note that when you turn the displays off they will rise to the
voltage that they are supplied from - this will be 9 volts if
you feed them directly and the PIC may not like it. If you use
drive resistors (as you should) then the PIC protection diodes
will conduct and MAY save you. Better design is to run the
displays from the 5 volt supply that the PIC is using.

A 7805 regulator in a TO220 package will supply the PIC and a
display happily and costs very little more than a 78L05 - the
78L05 is capable of lower power and will probably not have
enough capacity for a bright LED display.

LM7805s (same as LM340T5) or similar can be purchased from most
electronic suppliers who will also be able to supply a simple
circuit to use them.

----------
> From: Leo van Loon <sbb.simpeltron@TIP.NL>
> To: PICLIST@MITVMA.MIT.EDU
> Subject: 12c508 fed by 9V battery
> Date: Thursday, 16 July 1998 19:47
>
> Dear friends,
>
> I am producing an electronic dice with a PIC12C508 as a kit
for children.
> For simplicity I must use a 9V block battery, but the PIC does
not like 9V.
> How can I reduce 9V to 5V with a minimum of components?
> Does only a serial 4,7 V zener work?
> I feed the seven LED's of the display directly from the
battery, that can be
> no problem.
>
> Leo van Loon
> SBB simpeltronics
> Netherlands
> tel +31 (0481) 450034
> fax+31 (0481) 450051
> mail sbb.simpeltron@tip.nl
> url http://www.sbb-simpeltronics.nl
> SBB simpeltronics ontwikkelt technische projecten voor
basisschool en
> basisvorming.
> SBB simpeltronics develops technical projects for children in
primary and
> secondary education.