(Paraphrased from Afrotechmods.com due to content and language.)
bicostp's comments in blue.
Stuff you need from Home Depot:
Wall outlet - $0.38
Lamp dimmer - $4.89
Faceplate - $1.47
Box - a buck
A soldering iron if you don't already have one.
From junked power supply in CMU dumpster: (or Radioshack, wherever)
Power cord
Itty bitty LED
ARNOLD sized (1 watt) 15k resistor. (For people in 220v countries use a 30k resistor). If you can't get a 1W resistor, make one out of a bunch of series and parallel resistors. You will know your resistor was too small when things catch fire.
WARNING: This experiment involves REAL, 120 VOLT (220 for you foreigners) ELECTRICITY! THERE IS A HIGH RISK OF SHOCK IF YOU ARE NOT CAREFUL. KIDS, ASK AN ADULT TO HELP YOU. ADULTS, GET AN ADULT TO HELP YOU. YOU HAVE BEEN WARNED.
Cut off the end of the power cord, and figure out which wires are live, neutral, ground. It seems to be standard that black is live, white is neutral, green is ground, but just in case heres how you can safely check which is live- Set your multimeter to its highest AC voltage measurement setting. Separate all 3 bare wires a good amount. Connect one multimeter lead to the wire you want to test, and the other lead to your finger. Then plug in the power cord. The ground and neutral wires should give an almost 0 reading, and the live wire should be significantly higher. Since I was standing on a carpeted, wooden floor I only got a readout of 35V, but between live and neutral there was the normal 110V. So, basically, DO NOT touch ANYTHING with BARE METAL while this thing is plugged in. Pretend it's a museum piece, look, but don't touch. Just unplug it. As long as you're careful, and don't touch anything but the plug (to plug in and unplug), you're safe. This, come to think of it, is the most risky part.
Unplug the cord and thread it through your box. Use a lot of solder to firmly fix the ground wire to the ground plate of the wall outlet. Do the same with the neutral wire, and the neutral side of the outlet, which should be clearly labelled. Solder the lamp dimmer's green wire to the same point where you connected your ground wire. Then take one of the dimmer's black wires, and solder it to the power cord's live wire. Cover the soldering job with electrician's tape or something. Take the dimmer's other black wire and solder it to the live side of the wall outlet.
Use either a hot nail or a drill to poke out a little hole in the faceplate to let the LED through. Solder your resistor to one end of the LED. Solder on a little wire connecting the 'dimmed' live output to the resistor. Stick the dimmer onto the faceplate, and then solder the bare end of the LED onto the ground plate of the dimmer. Throw some glue and insulation in there. So now you should be able to trace a current path, live from mains->dimmer-> resistor -> LED -> ground.
Screwed anything up yet? Ok. Now screw everything up.
Plug your box into the wall, and plug in a soldering iron in, and play with the dimmer, and see how the voltage/LED brightness/iron temperature changes. And um... thats it.
Now be careful with electricity. With this box, you can have a professional soldering station for very little money.
Have fun! (And be careful.)DISCLAIMER: I assume NO responsibility for any injury or damages this my cause.
