> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu]On Behalf
> Of Cedric Chang
> Sent: 23 February 2007 03:23
> To: Microcontroller discussion list - Public.
> Subject: [EE]: Best way to detect current flow in 110VAC circuit
> 
> 
> I am looking for suggestions on the cheapest way to build a circuit
> that will sound an alarm if current is being drawn in a 110VAC circuit.
> I want it to be cheap, cheap and be powered by the 110VAC.
put your cuircuits "ground" point at the incoming mains live.

for power assuming you only need a small ammount of it use a resistive drop with a diode zener and capacitor to get a reasonablly regulated supply

then for detection put a shunt resistance (say 0.1 ohm 20W) in series with the output and handle the voltage on the other side of this like any other low voltage signal (at 13A it will be 1.3V AC relative to the incoming mains live).

DO NOT TOUCH THIS CUIRCUIT WHILE IT IS TURNED ON AND REMEMBER TO USE A SUITABLE ENCLOSURE AS THE WHOLE CUIRCUIT WILL BE LIVE.

> 
> I have a bad habit of leaving soldering irons,  hot glue guns and  
> test equipment
> on for days when I leave the lab.  I want to have something that  
> beeps every
> X minutes ( when power is being consumed )  and if I don't push a  
> button to reset
>   it, it gets more and more belligerent.
> 
> I would plug things I typically forget into a power strip that  
> contains this module.
> 
> I supposed a resettable timer would work as well, but it is not as cool.
> 
> Cedric
> 
> 
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