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The  $25 AC Speed Control

I have gotten a few messages sent to me and it seems to be a common question in the forum, so I thought I would post a tutorial on how to make your own speed control for an brushless AC motor for about $25 (that assumes you have a knife and a screwdriver, otherwise you have to buy tools). 

Keep in mind you need to watch your amps when building this: your powertool should have a sticker telling you the draw. For a 5amp motor, you're going to need a 7amp switch (min).


Your materials list:

(1) 120v, 7amp Push On/Off dimmer switch,  (check the ceiling fan section) - $6.00
(1) Medium duty extension cord, 8ft-12ft long  (make sure it has the 3rd prong for a ground wire) - $8.00
(1) Steel electrical box, single slot, min 2" deep - $1.00
(2) Romex wire connectors (make sure they are the same diameter as the holes in the electrical box) - $1.00
(1) Toggle switch cover - $1 to $5 depending on the style you chose

Optional - a handful of small cable ties just to keep everything neat and clean. 

NOTE: The dimmer switch should come with wire nuts for the connections and all the mounting hardware should be included for the faceplates.    

Step One - Prepare the Extension Cord

You know that brand new extension cord you just bought?  Well, you're about to cut it in half.  Well, not exactly in half...  Wherever you chose to cut the cord is where you are going to splice in the dimmer switch (speed control).  I prefer my control box to be closer to the end of the cord, so I make my cut about a 12" away from the female end. 

After you have made your cut, strip the ends of the wires so you're ready to go...  It should look something like the picture on the left. 

Step Two - Prepare the Electrical Box

You'll start by knocking out the holes where you want the wires to go in and out.  It shouldn't take much effort since the holes are pre-stamped.  I usually use the holes on each end but the choice is yours.  After you have your holes ready, insert the wire connectors and screw them in place.  Make sure to loosen the clamps so you can feed the wires through (you won't tighten them until the end).  After the wire connectors are in place, feed one of the spliced ends through each connector.  

Below are some more pics of the process: 

Step Three - Connect the Dimmer

This is where it gets a little tricky, but I will try to clear up the process...  Here are the three hints I will give you:
1) Always keep in mind where the electricity is coming from: wire in the male end first (the end that plugs in to the wall).
2) Your main priority is the black wire.  The white wire skips the dimmers switch and the green wire is wired in for safety. 
3) Follow the wiring guide for a Single Location Application (the guide for the dimmer I bought is on the right). 

I didn't take a picture of it (and I should have), but there are 4 wires coming out the back of the dimmer switch.  They come out in pairs - A red/black pair and a red/green pair. 

Now a common question/area for confusion is this: How do I know  how to wire this thing?  The wiring diagram tells you...   In looking at this diagram, it reads left to right.  The "Hot Black" line is the black wire from the male end of the extension cord (it's called "hot" since that is where the power is coming from).    This means you just wired the dimmer so the black wire is bringing electricity in to the dimmer. 

Now the power has to get out of the dimmer.  How?  Look at the wiring diagram...  The red wire (the one paired with the green wire) brings the power out.  You'll splice this red wire with the black wire from the female end of your extension cord (the end you'll plug your machine into). 

Wire up the white wires and the green wires, clean everything up with zip ties if you want, and move on to closing this up... 

Step Four - Tighten it Down and Lock it Up

Being somewhat gentle, push everything into the electrical box (it shouldn't be too difficult if your electrical box is deep enough) and tighten down the faceplate of the dimmer switch. The screws for the faceplate were provided with the dimmer switch and should line up with threaded holes on the electrical box. 

One that is done, you can tighten up the screws on the wire clamps so your extension cord doesn't get pulled out.  I usually tighten them to the point where the top band is just starting to flex a little. 

After that, mount your decorative face place (the holes should line up perfectly with the holes on the dimmer switch) and put the knob on...  

The Finished Product...
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