Ground Problems

Archiver

Hi ,
I have been working on a project where I get an external input from
a source. I am reading this value using the "input" function. Using
this function I read the length of zero and length of high signal.
When I do not get any input the signal has to read zero, but it keeps
reading random values. I guess this might be because of the
difference in ground between the input signal and the power supply(I
use a seperate power supply for both). Please help me solve this
problem.

Thanks

Mohammed

Archiver

At 10:52 07/10/01, Amin wrote:

> I have been working on a project where I get an external input from
>a source. I am reading this value using the "input" function. Using
>this function I read the length of zero and length of high signal.
>When I do not get any input the signal has to read zero, but it keeps
>reading random values. I guess this might be because of the
>difference in ground between the input signal and the power supply(I
>use a seperate power supply for both). Please help me solve this
>problem.

If you want an input pin to always read low (or high) when no signal is
present, you need to pull it low (or high) with a resistor connected to
ground (or +5 volts). A 10K ohm resistor should do the job unless your
signal source is exceptionally weak.


Jim H

Archiver

Thanks a Ton Jim.

I will check it out right away

Mohammed

--- In basicstamps@y..., Jim Higgins <HigginsJ@s...> wrote:
> At 10:52 07/10/01, Amin wrote:
>
> > I have been working on a project where I get an external input
from
> >a source. I am reading this value using the "input" function. Using
> >this function I read the length of zero and length of high signal.
> >When I do not get any input the signal has to read zero, but it
keeps
> >reading random values. I guess this might be because of the
> >difference in ground between the input signal and the power supply
(I
> >use a seperate power supply for both). Please help me solve this
> >problem.
>
> If you want an input pin to always read low (or high) when no
signal is
> present, you need to pull it low (or high) with a resistor
connected to
> ground (or +5 volts). A 10K ohm resistor should do the job unless
your
> signal source is exceptionally weak.
>
>
> Jim H

Archiver

Hi All,
Problem Solved. I tied the two grounds together and added a 10k
resistor. Works perfectly.

Thank You

Mohammed

--- In basicstamps@y..., "Amin" <md_amin_99@y...> wrote:
> Hi ,
> I have been working on a project where I get an external input
from
> a source. I am reading this value using the "input" function. Using
> this function I read the length of zero and length of high signal.
> When I do not get any input the signal has to read zero, but it
keeps
> reading random values. I guess this might be because of the
> difference in ground between the input signal and the power supply
(I
> use a seperate power supply for both). Please help me solve this
> problem.
>
> Thanks
>
> Mohammed

Archiver

At 18:04 07/10/01, Amin wrote:

>Hi All,
> Problem Solved. I tied the two grounds together and added a 10k
>resistor. Works perfectly.

Excellent! Thanks for letting us know what worked.


Jim H

Archiver

Hi All,
This might sound really wierd , but the stamp was working as it
was supposed to till today. now it has the same problem. Only this
time it does not read any input at all unless i ground the stamp
externally. If I see the operation through the debugger it works
right, but when u remove the ground pin from the parallel port,It
does not read any input. what do u think is the problemo..

Mohammed


--- In basicstamps@y..., Jim Higgins <HigginsJ@s...> wrote:
> At 18:04 07/10/01, Amin wrote:
>
> >Hi All,
> > Problem Solved. I tied the two grounds together and added a 10k
> >resistor. Works perfectly.
>
> Excellent! Thanks for letting us know what worked.
>
>
> Jim H