I have a switch in my wall which turns a outlet on and off, however I'm nearing maximum capacity on that circuit. I want to be able to plug more stuff into it so that I can turn it off with this same swich.

My idea is to somehow build a little box which plugs into 2 separate circuits, the one controlled by the switch, and another circuit which is on all the time. The box would also have a plug that I could plug a power strip into.

When the power to the circuit controlled by the switch is turned on, the box activates a relay which turns power on to the output which goes to the power strip, coming from that secondary circuit.


(Oops, spelled circuit incorrectly)

Does this make sense? In this way I can control more devices with my switch.

How could I build this? I know it'd use a relay, but what else? Safety concerns?

  • 1
    \$\begingroup\$ Are you convinced that wall box B is on a different fused circuit to wall box A? \$\endgroup\$
    – Andy aka
    Sep 16, 2013 at 19:03
  • \$\begingroup\$ Use less equipment or equipment with higher efficiency. Or upgrade your home wiring. \$\endgroup\$
    – jippie
    Sep 16, 2013 at 19:07
  • \$\begingroup\$ This is for stage lighting, it's much cheaper to build this than to convert to LED. \$\endgroup\$
    – James T
    Sep 17, 2013 at 1:43

1 Answer 1


Sure, this makes perfect sense. A DAYTON 5X847 relay would do the job. Its coil rating is 10VA at 120VAC, so you don't need to supply DC to the coil. When it receives 120VAC, it switches its DPDT contacts.

You would wire up the DPDT contacts to the live and neutral of your secondary circuit, routing them either nowhere (off) or to the power strip.

The relay is rated at >20 amperes so it will handle a full residential circuit.

  • \$\begingroup\$ Or if you are budget-conscious and want to live dangerously, you may opt for a lower-quality relay such as a Packard PR341 \$\endgroup\$
    – HL-SDK
    Sep 16, 2013 at 19:08
  • \$\begingroup\$ Would I need to also add some resistors or something? Or would just sticking a relay in a box with a couple of power cords and Edison plug work? (next to no resistance = infinite current?) \$\endgroup\$
    – James T
    Sep 17, 2013 at 1:46
  • \$\begingroup\$ Also, would it be cheaper to get a relay which is activated by a much lower voltage, and get a wall-wart to power the relay? \$\endgroup\$
    – James T
    Sep 17, 2013 at 1:48
  • 1
    \$\begingroup\$ Yes, you could use say -- a 5vdc relay and use a cheap AC/DC adapter if you would like to go that route. You do not need resistors for that application as the relay coil is rated for 120VAC. Likewise, a 5v relay activates with 5 volts on the coil. \$\endgroup\$
    – HL-SDK
    Sep 17, 2013 at 1:53

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