got one:
http://www.harborfreight.com/cpi/cta...emnumber=43060

works like a charm on 3 different motors I tried: a grinder from
Lowes, Craftsman trimmer and another trimmer from HF.

There were reports about difficulties with slow-start motors
but as you see I didn't have any problems. Was able to get all 3 to
start at the lowest RMP setting of the control and change the RMP
accross the whole range.

Just a PSA, no affiliation

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.

Bob Swinney
"mclorson" wrote in message
oups.com...
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

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

"Robert Swinney" wrote in message
...
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.

Bob Swinney
"mclorson" wrote in message
oups.com...
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

On Fri, 8 Jul 2005 06:56:18 -0700, "Mike Fields"
wrote:

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

Got to be three phase though.
Alec

"mclorson" wrote in message
oups.com...
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?

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

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:


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

wrote in message
ups.com...
DeepDiver wrote:

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.

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.

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
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