Any Ideas ??????????

[WJF]

I am trying to locate or help with a circuit that will monitor the current
on a mains cable and sound a short alarm should the current change. The
basic idea is for remote monitoring of a set of PIR controlled security
lights up to 10 seperate units at 500W each. I don't want to run a seperate
cable for each sensor so I thought this could be one solution. Any help or
ideas would be apreciated thanks for reading this post

 

[scada]

"WJF" <XXXXXXX@ZZZZZZZ.com> wrote in message
news:caerq8$1t7$1@news8.svr.pol.co.uk...

I am trying to locate or help with a circuit that will monitor the current
on a mains cable and sound a short alarm should the current change. The
basic idea is for remote monitoring of a set of PIR controlled security
lights up to 10 seperate units at 500W each. I don't want to run a
seperate
cable for each sensor so I thought this could be one solution. Any help or
ideas would be apreciated thanks for reading this post

I would start with a current transformer. One of the feed legs passes
through the center of the CT then the secondary of the CT goes to the
monitoring circuit which could be as simple as a current relay. A more
accurate circuit could be made using a suitable load resistor on the
secondary and measuring the voltage drop across the resistor, the amplitude
of the voltage corresponds to the load current. A simple comparator circuit
could determine the alarm point. Just remember to ALWAYS LOAD THE SECONDARY!
An open CT secondary will produce high voltages that can destroy both the CT
and anyone in its path!!!