Or use a PIC with A/D inputs.

With a full scale range of 0..5V you'll have about 50 counts at 0.5V.

Treat anything over 25 counts as a '1'.

More than enough room.

You could even use a lower reference voltage and get a bigger swing.

Bob Ammerman
RAm Systems


----- Original Message -----
From: "Byron A Jeff" <byron@CC.GATECH.EDU>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Monday, March 10, 2003 8:57 PM
Subject: Re: [PIC]: Voltage to bytes conversion


> On Mon, Mar 10, 2003 at 11:37:48PM +0000, Laura Adamson wrote:
> > I chose the PIC16c84 because it was the chip that uni had the most
> > information on, other than that there is no reason for using that
particualr
> > chip.
> >
>
> Understood. We have a lot of reasons why you should consider upgrading.
> I've summarized them here:
>
> http://www.finitesite.com/d3jsys/16F628.html
>
> All of the arguments listed apply to the 16F87X, 12F675/12F629, and the
> 16F676 familes of parts.
>
> > The voltages will be between 0v and 0.5v.
> > There will be up to 8 inputs.
> > I need the outputted byte stream to tell the PC which input source it is
> > looking at and whether it is high or low, for each of the sources in
turn,
> > running in a loop. E.g. 0011 would mean source 1 is high and 0100 would
mean
> > source 2 is low.
>
> A raw PIC won't be able to discern 0V and 0.5V. So you'll need a voltage
> multiplier, or an external comparator to differentiate. Something like a
> couple of LM339 quad comparators should do the trick. Attach to PORTB,
turn
> on the weak pullups. Generate a 0.25V reference voltage using a couple of
> precision resistors, and off you go.
>
> BAJ
>
> --
> http://www.piclist.com hint: The PICList is archived three different
> ways.  See http://www.piclist.com/#archives for details.
>

--
http://www.piclist.com hint: The PICList is archived three different
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