Howard, I'm anxious to see the piclisters reaction at your mail...
( At least what Olin says :) )

My answer will be no, because:
1. the protective diodes on any pic pin which will open partially your led
at (12-5-Vled-0.6)/Rbalast when the pin is input or the leds which will
light ( just a little ) when the pic pin is output high. ( this can be
avoid using a zenner in series with the anode but anyway don't solve your
problem )
2. the requiring of an oped drain pic pin which will let you to drive only
8.5V ( midrange pics ) and just one led

So, you need a voltage converter to drive 7 seg directly from +12.


regards,
Vasile
http://www.geocities.com/vsurducan


On Mon, 13 Jan 2003, Howard Simpson wrote:

> Hi All,
>         Does anyone see a problem with controlling an LED by applying 12 volts
> to the anode, through an appropriate resistor, to a port, and switching
> the LED on with an 0?  (4 seven seg displays in this case, multiplexed
> one at a time)
>         I thought that perhaps 12 volts might appear momentarily on the port,
> before the resistor dropped the voltage.
>         Or, can 12 volts "leak" back through the LED.  It shouldn't, but I have
> no way to measure any 12 volt spikes which may cause a problem with the
> port.
>         A bit wierd, I know, but the idea is the PIC runs for hours doing it's
> thing before it's necessary to have a look at the LED display, by
> pressing a button and turning it on for a short time.
>         As it's battery powered, I was hoping to use an efficient switch mode
> regulator to save battery power, and not have to have the regulator
> supply a few mA for the PIC, then be required to supply 80 mA or so for
> one segment per display from time to time.
>         The battery is 12 volts because it's huge.  This thing is required to
> run for months without charging.  I'm looking at 6 volt dry cell
> batteries with a switch mode regulator, and same question applies to 6
> volts as it does to 12.  (Hmmmm... only have to dump one volt this way
> tho!)
>
> Regards to all, and much appreciations to those who seem tireless in
> answering problem, even if they show some frustration from time to time.
> Howard Simpson
>
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