Step 1: So Why?
I do a lot of project work on motorcycles and motorcycle-shop-related electronics, namely cordless phones which do not survive well in a shop environment. I use my dremel for a veriety of things, at several different speed settings, but the tool has a simple slider on the body to control on/off and speed, and it's aggrivating to have to reach up and slide it all the way off because i need to use that hand to hold something else, and then have to try and get the speed right again 10 seconds later. This way I can just tap a switch with my foot, needing zero hands free to control the power- AND the Dremel can be left at a specific speed setting, with no fiddling around needed to get back to that setting later.
Step 2: Parts and Tools Needed
- Extension Cord (New 7' extension cord) $3.97
- SPST Pushbutton Switch (Guitar Pedal Switch, DigiKey #432-1212) $3.56
- 4x4x1.5" electrical box $1.18
- 4" square electrical box cover with 3/8 center blank $0.77
- 5/16" flat washers (2) $0.32
- 3/8" NM Electrical Box Cable Connector $0.38
- Needlenose Pliers
- Phillips Screwdriver
- Soldering Equipment (Pencil, Solder)
- Shrink Wrap and/or Electrical Tape
- Box Cutter / Razor Knife
- Wire Strippers
- Optional: Duck Tape
Your washer sizing will need to correspond to what size the mounting hole for the switch you are using is. The washer needs to have a center hole just large enough for the switch mounting threads to fit through, and have a large enough diameter to completely cover the hole in the 4" square cover top plate.
Step 3: Determine Length & Cut the Cord
The first thing you need to do is find out how long of an extension cord you are going to need. Keep in mind that the cord needs to be long enough to reach from whatever outlet you are using, down to the floor beneath your feet, and over to a place that the tool you are plugging into it can reach the outlet. Wiring the box itself should use about 8" of the total length of the extension cord. You'll also want to have some extra length from the plug to the switchbox, so you can reposition the switchbox to be near your foot as you work. I ended up making the first 5ft or so of the extension cord the "plug" side, and only about 1.5ft the "outlet" side.
Once you have found where on the cord you want to put the switch box, mark it with a piece of tape.
The next thing you need to do is determine which of the two wires in the extension cord you need to cut. Most extension cords are "zip cord", they look somewhat like speaker line and have 2 individually insulated wires joined by a thinner section of plastic. One of these wires is the hot ( +110VAC ) wire, and the other is neutral/ground.
The best way to determine which wire is the hot wire is to look at the plug. On American 110-volt plugs, there is a wide and a narrow blade. The narrow blade is the hot conductor, and the wide blade is the neutral conductor. If you lay the plug out flat with the narrow blade on the left, the left insulated wire is probably the hot wire.
Go back to your taped spot on the extension cord, and carefully slice the thin plastic joiner between the two wires on the zip cord, for about 3". Then cut the "hot" wire. You can check to ensure you cut the right wire with a multimeter's conductivity tester. If you cut the wrong wire, you can either solder that wire back together and cut the other wire, or discard that extension cord and use another.
Step 4: Solder Time!
Now, take the NM Flat Cable Connector junction box clamp and loosen the clamp, and then slide it over the looped end of the extension cord, past the zip tie.
WARNING: Do you see that thin finger nut on the inside (threaded) part of the clamp? Take that off! If you don't take that off you'll end up having to unsolder things later and you won't be very happy, will you?
Okay, now pull the bottom loop of continuous conductor away from the cut ends, strip them back, and tin the wires. If you don't know how to do this, there are Instructables to help you out.
Step 5: More Soldering, and What Not to Do
Okay, now pick a 3/8 punch-blank in the side of the 4"x4" electrical box, and punch it out with your needle nose pliers ( or other generic tool ). Slide the tinned wire leads through the hole, and thread the cable clamp's threaded nut over the tinned ends, so it is against the inside wall of the box. Pull through a few more inches of cable, to give you some working space.
Now, go ahead and solder on your switch- but DO NOT forget to put your shrink wrap up the wires first, or you will end up having to unsolder and resolder the switch!
Now, if you've done everything correctly, you should have the wire running through a hole in the electrical box, and a switch soldered and shrink-wrapped or otherwise insulated. If you did what I did the first time, and screwed up, you will have something like what's in the third picture- a switch, with no way to fasten the cable clamp to the box. Get another beer, cut the shrink-wrap, desolder the wires, and fix it. After all, it's not like you haven't done this before.
Step 6: Mounting the Switch, Finishing Up
Now, push the excess extension cord back through the hole in the junction box, leaving a few inches of play to install the top plate with. Thread the clamp nut on the clamp threads, and tighten by finger and then with a pair of pliers, until the clamp will not rotate against the junction box. Line up the two pieces of extension cord that go through the clamp, and tighten the clamp down just enough to hold the cords where they will not slip.
Slide the top plate onto the screws in the junction box, and snug down the screws. You're done!
Be sure to test the footswitch with a multimeter or by plugging a light into the extension cord's outlet and pushing the switch. The light should turn on and off as you push the switch.
Hook it up and go do another Instructable!
Step 7: Final Thoughts
- To make a much longer plug / outlet cord, you can use 16-gauge solid-color insulated speaker wire or replacement lamp cord wire, and buy a replacement plug and outlet. The cost of a replacement plug and outlet is similar to what a standard extension cord costs, however.
- Adding duck tape or some other form of tape to the bottom of the junction box helps to keep it from shifting on a concrete or hard floor, and also keeps it from scratching the floor
- A momentary contact switch could be used instead of an on / off switch, providing a "dead man"-type of safety, as well as an even easier method of switching for fast on/off power situations. I decided to use an on/off switch because I tend to shift in my seat a lot as I work, and having to keep one foot in exactly the same place would be inconveniant.
- A grounded (3-prong outlet) version of this could be made, you would just need to pass the ground wire through a screw in the junction box to ground the box as well. Also, most 3-prong grounded style appliances draw several amps, so a heavy-duty switch is called for.
- you could use a standard wall light switch instead of a pushbutton switch, or even a regular toggle switch. However, this would require that you remain in stocking or bare feet for the duration of using the switch. In using this switch I find I can comfortably actuate it sitting or standing, wearing shoes or in stocking or bare feet.
- A larger actuation surface would be nice for bare-foot uses, as the small area of the switch head tends to cause my toe to slide off to one side and not actuate the switch. This is a minimal issue, however, and could easily be rectified.