# Home made variable speed.



## BHOFM (Oct 14, 2008)

On a whim I went to Lowes and bought a cheap
light dimmer, $4, 600w.

I put it in a circuit box with a plug and outlet.

It works fine on my B&D mouse sander, Makitia sander,
old Snapon corded drill, 1/4 sheet sander.

It does not work on my Dremiel, routers, band saw
drum sander or drill press. They all run at full speed
no matter where you set the dimmer. Does not work
on the scroll saw either.

But all in all, for the mouse sander it is worth while
when doing fine work.

Total cost, less than $5. Used an old extension cord
I had laying around.

There is a fire warning when using the dimmer with
motors so I put it in a metal box and keep it on the
table where I can watch it. It has not gotten hot
yet and I have run it for nearly an hour non stop.


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## woodnthings (Jan 24, 2009)

*Just a caution*

600 watts is only 5 amps at 120 volts. Motors without brushes like on power tools will not like that system and may fail. Just be careful what you try to use with it. Don't experiment with anything you don't want to blow up or burn out! :laughing: bill


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## BHOFM (Oct 14, 2008)

woodnthings said:


> 600 watts is only 5 amps at 120 volts. Motors without brushes like on power tools will not like that system and may fail. Just be careful what you try to use with it. Don't experiment with anything you don't want to blow up or burn out! :laughing: bill


It does not work on capacitor start motors. They run
at full speed at any settings.

The little sander is .5 amp. The drill is 1.5.
The Dremel must have a solid state thing it
in, it doesn't run at all. The routers growl.

Like I said, it was mainly for the little sander and
it works fine.


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## rrich (Jun 24, 2009)

Generally speaking....

The speed of motors with brushes is voltage dependent.

The speed of capacitor start motors is frequency dependent.

USUALLY, the light switch dimmers work by chopping the AC Sine wave to fewer degrees. (Half of a 60 cycle Sine wave is 180°. To dim the bulb, the electronics may not turn the bulb on until 60° into the cycle giving the bulb only 2/3 of the energy necessary to generate the heat for incandescence.) This technique works very well with incandescent light bulbs. There is a dimmer that can work with fluorescent bulbs. This dimmer sends less than all of the AC cycles to the bulb. (These don't always work that well.)

Although your set up may be working with your mouse sander, I am unsure of the actual electronic process that is slowing the sander. I don't know if it is safe or not. I would like to hear of any surprises that you may encounter with the set up.


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## eccentrictinkerer (Feb 18, 2009)

Using an ordinary dimmer switch on anything but an incandescent load is extremely risky!

These dimmers are designed to operate with pure-resistive or incandescent loads ONLY!

Dimmers use phase-angle control to reduce power to the load. When used with an inductive load, the dimmer may deliver power that 'looks like' direct current which can fry the device.

Remember, when you let the magic smoke out of your tool it will no longer work!:no:


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## Texas Sawduster (Apr 27, 2009)

*Router speed control*

As already posted using a light dimmer is very risky.
I have been told NOT to use a router speed control on a soft start router just for that very reason. Not sure exaclty why but if you run a dimmer switch you do not get enough voltage to the motor and you may actually burn it up, especially if your router "growl".


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## BHOFM (Oct 14, 2008)

I checked it on about every tool in the shop, not the
table saw.:laughing:

I got it to see if the little sander would work, and it
does, very well. As stated, it is .5 amp brushed motor.

I understand the risk and am willing to chance it on
small tools.

I have run the mouse sander several hours now, once
for about an hour non stop with no ill effects that I can
see or smell.

Anyone else that tries this should be aware of the
risk as well.

I will keep you posted as to any bad results of my
experiment.


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## eccentrictinkerer (Feb 18, 2009)

After thinking about it for a while I should have answered differently. Sorry. 

The dimmer will work OK with many series wound AC motors, 'universal' motors and brush-type motors.

Inductive motors can see the voltage provided by a dimmer switch as DC. Motors such as this will probably be fried quickly. ( A safe way to check things out is to put a 100 watt bulb in series with the motor and the dimmer. This will limit the worst-case current to an amp or so.)

The trick is to know exactly what type of motor you have.

Router speed controllers are like a fancy dimmer switch a circuit that senses the back-emf of the motor. This feature will cause the controller to increase the applied voltage in response to load.

Good luck and 'Be careful out there'!:smile:


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## BHOFM (Oct 14, 2008)

No problem. I have an above basic understanding of
electricity, motors, circuits and such. I can read
schematics and decode components. 

I was a ham radio operator for many years.


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