How are you going to monitor this detection method?  

For instance, you could add a pilot lamp of some sort.  If you look at
it and the lamp is out, it's probably unplugged.   Or the other side of
the coin is you would monitor it remotely by some sort of panel or even
a 
Video screen.  The solutions offered will necessarily depend on how you
intend to monitor the function.
Will it be a visual check in close proximity to the device that is being
powered.  Or will it need to be monitored remotely?   And if remotely,
how far away, and what is at your disposal in the way of monitoring
equipment?  


 
Regards,

	
Jim

-----Original Message-----
From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf
Of alan smith
Sent: Thursday, May 10, 2007 1:50 PM
To: Microcontroller discussion list - Public.
Subject: [EE] Detection of getting unplugged

Well, I've been trying to solve a particular problem for a few months,
sorta on again, off again issues.
   
  Simply put, I need to know when something has been unplugged from a AC
socket.  I don't care about how much current its drawing (I do...but I
dont need to know), because in some cases it might be a 100mA wall wart
and in other cases a 100W power supply.  I just want to know....did it
get unplugged.
   
  I've looked at some exotic solutions like power monitor chips but they
aren't really designed for this.  I've played with Allegro hall sensors
but the sit at 2.5V nominal, and just mimic the AC waveform and yes,
with a larger load I can see it but smaller devices do not make a large
enoough effect even when I use a simple gain stage op-amp.
   
  Nothing really gives a solution to cover all the ranges.  I need it
small, cheap and simple to build.  (think production enviroment).
   
   
  So, any good ideas out there?

 
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