# Can I use a dimmer switch to add variable speed?



## jtreagan (Jun 9, 2015)

My little Delta 1X30 belt sander simply runs too fast for the job I'm working on. I need to slow it down. Would it work to add a dimmer switch to the power cord to get variable speed? Has anyone done this? Any other ideas?


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## GeorgeC (Jul 30, 2008)

Wrong. 

George


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## ryan50hrl (Jun 30, 2012)

That depends....if it's a brush type universal motor you can use one of these. 

http://m.harborfreight.com/router-speed-control-43060.html?utm_referrer=direct/not provided

If it's an induction motor than no..


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## TimPa (Jan 27, 2010)

there are rheostat style dimmers and new digital dimmers, i wouldn't try either. if the motor has brushes, you need a speed controller....


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## PhilBa (Jun 30, 2014)

even if it works, you don't want to use a dimmer because the standard ones are only rated for 600 watts - about 5 Amps. They all use what's called phase control but you want something a lot more beefy than that.


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## Chamfer (Sep 6, 2014)

Forget the light switch.

You need a speed controller. What kind you need depends on the motor, as Ryan stated. You can buy variable speed controllers for both universal (synchronous) motors and induction (asynchronous) motors. They are generally relatively inexpensive although slightly more than a dimmer switch for a light.


Figure out what kind of motor you have and go from there.


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## Steve Neul (Sep 2, 2011)

On lights you can dim them by lowering the voltage. On a AC motor you have to adjust the frequency to change the speed.


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## 1Joe (May 14, 2014)

Router speed controller at Harbor Freight for $19.99. Do it.


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## pweller (Mar 10, 2014)

Chamfer said:


> Forget the light switch.
> 
> You need a speed controller. What kind you need depends on the motor, as Ryan stated. You can buy variable speed controllers for both universal (synchronous) motors and induction (asynchronous) motors. They are generally relatively inexpensive although slightly more than a dimmer switch for a light.
> 
> ...


How do you tell which kind of motor you have? It is just brushes vs. no brushes? And, will the brushes always be obvious?


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## Chamfer (Sep 6, 2014)

Without getting too technical, GENERALLY induction motors are belt driven whereas universal motors are gear driven. That should be pretty easy to decipher. 

Brushed and brushless are normally terms reserved for direct drive motors (universal).


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## TimPa (Jan 27, 2010)

pweller said:


> How do you tell which kind of motor you have? It is just brushes vs. no brushes? And, will the brushes always be obvious?


look in the literature if you have any on the unit. tell tale signs are 2 round caps that screw into the side of the motor, they are opposing each other. these caps allow easy access to replace brushes. some models don't have caps, and a cover has to be removed to access the brushes.

brush motors will typically emit sparks when running, if you look into the vent holes on the end of the motor (circular saws, drill, router, angle grinder, etc.). 

your sander is most likely brush type, or universal motor. meaning that it actually could run on 120 volts DC as well as AC.


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## jtreagan (Jun 9, 2015)

I picked up this little sander on a yard sale several years ago. Fellow had died and his kids were letting things go. It came attached to a bench along with a small router table/old craftsman router. It's been quite handy for lots of small jobs. Anyway, I surprised myself this morning by finding the owner's manual. It must have come with the tool when I bought it. Unfortunately, the parts breakdown tells me nothing about the motor -- just shows it as a single unit with a single part number. There aren't any brush access ports, although I have worked on brushed motors in the past that didn't have brush ports. Basically, I'm pretty ignorant about this electrical stuff, so any advice will be appreciated. A couple of pics are attached -- can you tell anything from the motor label? It only pulls 2 amps, so would a light dimmer switch work? I'm trying to do this as cheaply as I can.


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