ADC831 into stamp

Archiver

Hi guys.

having a bit of a problem bringing an input from an ADC831 A/D
converter into a Stamp 2. The input is from a 12VDC input, so I am
using a 10K POT across the 12V and run into PIN2 on the ADC. I then
have the chip powered and grounded on pins5&8 and Pins3&4.

Into the stamp I have ADC Pin6 into Pin12 on the stamp, ADC PIN7
into Pin 11 and ADC PIN1 into PIN10. (same as stampworks exp. #27
actually)

I have a pretty basic program, same as #27, but it just keeps giving
me 255 as the value it gets from the chip. Doesn't matter what the
input voltage is?

any ideas?
Thanks
JOdy Gallant CET
Shadcomm Ltd.

Archiver

I haven't looked at #27, but knowing the voltage at pins 2 & 5 would help.
If I am interpreting your description correctly, you qre using the 10k pot
as a voltage divider for your analog signal in. It can not be greater than
Vref, and certainly not greater than Vcc, ever.
How are you getting the 5V for Vcc, do you also have a 5V supply for this?
Forgive me if I am explaining what you already know, but the ADC0831 will
measure the difference between Vin+ & Vin-. Vref is used to setthe high end
of the range - the voltage level at which the ADC will output 255. If you
have a fixed 5V on ADC pins 5 & 8, with pins 3 & 4 grounded, any value that
is 5V or less at pin 2 should give you the proper output, as long as the
grounds are all connected.
C

>
ps: with a mopar you may go slow-far, but with a chevrolet, you'll get away.
(just an old saying I once heard - not really my opinion.)
pss; is it true that mopar brake calipers now have plastic pistons???
>
> Hi guys.
>
> having a bit of a problem bringing an input from an ADC831 A/D
> converter into a Stamp 2. The input is from a 12VDC input, so I am
> using a 10K POT across the 12V and run into PIN2 on the ADC. I then
> have the chip powered and grounded on pins5&8 and Pins3&4.
>
> Into the stamp I have ADC Pin6 into Pin12 on the stamp, ADC PIN7
> into Pin 11 and ADC PIN1 into PIN10. (same as stampworks exp. #27
> actually)
>
> I have a pretty basic program, same as #27, but it just keeps giving
> me 255 as the value it gets from the chip. Doesn't matter what the
> input voltage is?
>
> any ideas?
> Thanks
> JOdy Gallant CET
> Shadcomm Ltd.
>

Archiver

Yes, I am using the 10K pot as a voltage divider. Pin 2 has a
voltage of about 4.8VDC when the input is 12V, and I have a 7805
Regulator feeding 5VDC to PINS5&8 and PINS3&4 are gounded. The idea
was to use the voltage divider to Scale the 12V input so it could be
converted by the ADC and read by the stamp. Then, I could read a
low battery condition when the voltage fell below a certain
threshold.

My next step is to take it out of circuit and try it.

Thanks for the help. At least I know I have the proper inputs.

Jody


--- In basicstamps@y..., "Chris Loiacono \(E-mail\)" <chris01@t...>
wrote:
> I haven't looked at #27, but knowing the voltage at pins 2 & 5
would help.
> If I am interpreting your description correctly, you qre using the
10k pot
> as a voltage divider for your analog signal in. It can not be
greater than
> Vref, and certainly not greater than Vcc, ever.
> How are you getting the 5V for Vcc, do you also have a 5V supply
for this?
> Forgive me if I am explaining what you already know, but the
ADC0831 will
> measure the difference between Vin+ & Vin-. Vref is used to setthe
high end
> of the range - the voltage level at which the ADC will output 255.
If you
> have a fixed 5V on ADC pins 5 & 8, with pins 3 & 4 grounded, any
value that
> is 5V or less at pin 2 should give you the proper output, as long
as the
> grounds are all connected.
> C
>
> >
> ps: with a mopar you may go slow-far, but with a chevrolet, you'll
get away.
> (just an old saying I once heard - not really my opinion.)
> pss; is it true that mopar brake calipers now have plastic
pistons???
> >
> > Hi guys.
> >
> > having a bit of a problem bringing an input from an ADC831 A/D
> > converter into a Stamp 2. The input is from a 12VDC input, so I
am
> > using a 10K POT across the 12V and run into PIN2 on the ADC. I
then
> > have the chip powered and grounded on pins5&8 and Pins3&4.
> >
> > Into the stamp I have ADC Pin6 into Pin12 on the stamp, ADC PIN7
> > into Pin 11 and ADC PIN1 into PIN10. (same as stampworks exp. #27
> > actually)
> >
> > I have a pretty basic program, same as #27, but it just keeps
giving
> > me 255 as the value it gets from the chip. Doesn't matter what
the
> > input voltage is?
> >
> > any ideas?
> > Thanks
> > JOdy Gallant CET
> > Shadcomm Ltd.
> >