On 5/9/06, Dwayne Reid <dwayner@planet.eon.net> wrote:
>
> At 11:26 AM 5/9/2006, alan smith wrote:
> >This is a busy week for....what/how games I suppose....
> >
> >
> >   Want to detect not that a device is plugged into a socket...but
> > look to see if its turned on...ie.....is the device drawing any
> > current, thus its running.
> >
> >   Initial thoughts.....hall sensor that drives a bridge and then
> > look for a DC threshold value.  (hall sensors used for AC current
> > detect will mimic the AC waveform and increase the amplitude as
> > more current passes thru the field while also provide isolation).




I do this in some solutions and use just an optocoupler and a 555. I set up
the 555 as a missing pulse detector and trigger it with the output frm the
opamp. This way I have an output on the 555 that is high as long as long as
a device is turned on and goes to zero when its gone.

I have a variant of it in the HULK project (
http://www.vscp.org/wiki/doku.php?id=the_hulk_ii_-_the_hulk_ii) but where
the missing pulse detector is wrong.

Regards
/Ake
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