🚀 go-pugleaf

Here is some Comparator information.

http://home.cogeco.ca/~rpaisley4/Comparators.html

  You could adapt one of the time delay circuits about 1/2 way down
the page to eliminate any jitter but it should not be a problem with
such a large spread between the high and low current levels.

  At 725 milliamps the voltage  drop across 0.3 ohms should be about
0.22 Volts

  Use a threshold voltage of about 0.1 Volts.  This will give a
detection level of about 330 milliamps.

  This is assuming the resistor is in the common side of the circuit. 
If it is in the supply side a simple comparator will not work.

Rob.


"Werner" <Werner@NoSpam.com> wrote in message news:<Cfsra.66831$t_2.6142@afrodite.telenet-ops.be>...
> Hi fellow electronics enthusiasts,
> 
> I'm trying to build a on/off detection circuit, which is able to check if
> the connected LCD monitor TV is in standby mode (31 mAmps/12 volts) or
> active mode (725 mAmps/12 volts). I have put a 0.3 Ohm resistance in series
> with the 12 Volts DC power supply, so I have a small voltage drop across my
> 0.3 Ohm resistance, maybe enough to measure this drop using an LM311
> comparator IC.
> 
> But I'm afraid that the LM311 might go into an oscillation state as the
> voltage drop is small ... so I've thought about adding an LM318 (diff.
> amplifier) in front of the LM311 to boost the voltage drop signal ... but I
> don't seem to be able to get this to work correctly. Both LM's I would like
> to power off the 12 Volts DC supply of the LCD monitor.
> 
> Can anybody suggest? How to wire it up?
> 
> Thanks a million,
> 
> 
> Werner