>
> > I didn't draw the VDivider, to reduce 0V to 15V into 0V to 5V.
> >
> > V -/\/\/\----+----/\/\/\---- RA3
> > 2KR | 100R
> > -----
> > -----
> > |
> > GND
>
> What strange way to divide voltage, except if you are
> talking about AC, mostly high frequency. For DC, the
> capacitor doesn't divide anything with the 2KR.
>
> Ok, here goes a little bit of Ohm's Law:
>
> The correct way is:
>
> +Vin (15V)
> |
> R1 = 2/3 (R1+R2) 15k
> |
> +----o Vout = 1/3 (Vin)
> |
> R2 = 1/3 (R1+R2) 7k5
> |
> Gnd
>
> The simple voltage dividing formula is:
>
> Vin
> Vout = -------------
> ( R1/R2 + 1 )
>
> This formula derives from this one:
>
> The voltage across R2 (VR2) is the result of the multiplication
> between R2 Resistance in Ohms and the Current that crosses
> it. The current (I) is the result of the division of the VIN
> by the total circuit resistance R1 + R2. Using this two
> expressions together you have:
>
> VR2 = I x R2 and I = Vin / (R1+R2)
>
> Changing I by Vin/(R1+R2) you have
>
> Vin R2
> VR2 = ------- x R2 or Vin x -------
> R1 + R2 R1 + R2
>
> or MMC
>
> R2/R2 1
> VR2 = Vin x ------------- = Vin x ----------
> R1/R2 + R2/R2 R1/R2 + 1
>
> or
> R2
> VR2 = Vin x ( ---- + 1)
> R1
>
> --------------------------------------------------------
> Wagner Lipnharski - UST Research Inc. - Orlando, Florida
> Forum and microcontroller web site: http:/
http://www.ustr.net
> Microcontrollers Survey:
http://www.ustr.net/tellme.htm