On page 112 of MAKE Volume 05 (“How to Build a Power Tap”), we ran an illustration that could cause some confusion as well as a tripped circuit breaker. The illustration does not match the instructions (which are correct). The illustration shows a dual plug receptacle, which, when wired improperly, can cause a short circuit. If you attach the wires from the extension cord to the screws on the same side of the receptacle, it will create a short circuit. Don’t do that. Instead, follow the instructions and attach a wire to “each side of the electrical outlet.”
It’s better to use a single plug receptacle, not a dual-plug receptacle, because there aren’t as many terminal screws, making it less likely that you’ll make a mistake with the wiring. If you use a single plug receptacle, steer clear of the green ground screw, and follow the wiring instructions provided by the receptacle manufacturer, you should be in good shape.
Please refer to the illustration shown here when making the power tap.
(Note: do not plug anything into the receptacle that requires more than about 200 watts.)
Thanks to Paul L. Howard for being the first to point this out. We’re sending him a copy of our book, Makers : All Kinds of People Making Amazing Things In Their Backyard, Basement or Garage.