router speed control - real deal

Interesting, I tried to make a similar device using a lamp/light dimmer and a switch to use on my grinder. The grinder would start slow, but soon speed up to almost full speed. I couldn't get the dimmer to control the speed. I assumed I was using the wrong dimmer switch arrangement. Any homebrew ways of doing this?

-Mike

An incandescent lamp dimmer is a different animal than a universal AC/DC brush-type motor speed control such as the one sold by HF. They are not interchangeable.

The key here is the type of motor you are trying to control. If it is a "universal" type (ac/dc with brushes), you can easily control it with a solid state "dimmer type" control (although some work better than others). If the motor is an induction motor (like many grinders etc - no brushes, uses the rotating AC magnetic field to spin it), the only real way to control it is with a variable frequency drive since the speed of the motor is determined by the frequency of the AC applied to the windings.

mikey

I just purchased the Harbor Freight speed control unit (#43060) last week on sale for $12.99. At that price, why would anyone want to mess with a makeshift dimmer-switch control? Even if it worked as well, you'd spend more money just acquiring the parts.

- Michael

Got to be three phase though. Alec

The light dimmer-switch controls work fine on universal motors. And depending on how well you are at finding gems in the trash, they are free. The little ones are only good for 600 watts, but I found a couple of 2 kw ones some where.

Dan

DeepDiver wrote:

Sure, you can scavenge parts. But you need more than just a dimmer-switch: you also need -- at a minimum -- a grounded power cord, a grounded outlet, and some kind of chassis. Admittedly, these too may be scrounged. But then you add your time to the project, and by the time you're done, have you really saved $13? And all that time and effort for a less-featured unit.

Projects such as these are great for teaching kids about electronics, but they offer little in the way of true savings. Personally, I'd rather buy the commercial unit and spend my time making something that can't be readily (or cheaply) purchased.

- Michael

I can't disagree with your logic. I am sure it is true for you. For me a trip to the Harbor Freight Store is 7 miles to the Ferry, a fourty minute ferry ride, and about twenty more miles to Harbor Freight.

Some years ago, I put a light dimmer in a double wide steel junction along with a duplex outlet and a line cord. I mostly use it for controling the temperature of soldering irons, lowering the line voltage when troubleshooting TV's, etc. It did take a little time to put it together, but less time than it takes to catch the ferry.

So what are the extra features of the Harbor Freight unit?

Dan Caster Bainbridge Island, Wa.

DeepDiver wrote: But then

While I've lived closer to HF stores in the past, I too am a bit of a drive from the nearest location now: about 40-45 minutes drive to Vallejo. So I don't hop in the car and drive up there whenever I need something. What I do is consolidate my shopping trips. It turns out that Vallejo also has the closest steel yard for me and a few other stores that are not local. And there are times when I'm on (or returning) from a trip North, so stopping at the HF is not an extra expense (time or fuel).

Not a lot, but some little things that may or may not be important:

1. A separate three-position switch that turns the unit off, on through speed control, or on full.
2. A fuse for overload protection.
3. Probably a better heat sink designed to handle the power load of small tool motors.
4. A nice, professional-looking, compact package.

- Michael

I like the idea of that switch. When controling a soldering iron, it would be nice to switch to full power and back to a keep it warm level. No easy way to add that to mine. The 2000 watt dimmer that I have are big enough that I would need a triple size junction box to hald it and a duplex outlet. Dan

Well, you could replace the receptacle with the switch and use a pigtail in place of the receptacle. Bob

It uses a circuit that purports to be responsive to motor back EMF, thus providing better speed control of a motor. That's a bit of a reach because it s a dirt simple circuit, but this circuit is documented in the old GE SCR manual circa 70's or so.