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Automatic Power Switch Answered

I am looking for someone who is McGuyver-like and able to show me how to build an outlet that allows me to plug in a power tool like say a miter saw and a shop vac. When the outlet senses a power draw from the saw, it`ll power the vacuum to start as well then when the miter is stopped so will the shop vac. I know Craftsman makes this very switch ( http://www.sears.com/shc/s/p_10153_12605_00924031000P?keyword=auto+switch ) however since it cannot be brought in to Canada, any makers out there?


In the past I have used a computer power saving switch magig (like this) for this very application.  You might have them available in Canada? They basically turn on some plugs (which usually go to a whole bunch of computer peripheral devices) when then sense that the main CPU has been turned on.  Same with turning off (with a 5 sec or so delay)..

As long as you shop vac is not too power hungry - it worked well enough for me.A slight lag time when you turn on the power tool to when the vac comes on - but not bad..   

You could just hack the power supply so that both saw and vac' are operated through a common switch. Foot-operated perhaps?


I didn't recognize that acronym RCD at first either, and that's because in the former United States RCDs are called GFIs or somtimes GFCIs. Curiously the Italians call them "salvavitas". This is all according to the Wiki article linked below:<br /> <br /> <a href="http://en.wikipedia.org/wiki/Residual-current_device">http://en.wikipedia.org/wiki/Residual-current_device</a><br />

Make yourself or buy a small current transformer (CT)- you could wind one if you can get a toroid core. Put one of the wires to the appliance through it. Measure the voltage on the output of the coil (put a load resistor across the CT), rectify it, either with a diode . Use the output to switch a relay.

Alternatively, and this is winging it, an RCD does most of what you want - it meaures the imbalance between TWO windings on a transformer, and switches if it detects one. Your job is to make that happen. NONE of this is "Safe" unless you are skilled in working at mains voltages, but you can probably extract the guts of what you need from an RCD.


Although your terms are confusing to me I do get the gist of it. It might be simpler to make an american friend lol. Thank you so much for your time and responses.