# Pot wiring help needed



## bill stupak (Dec 29, 2019)

I am re-purposing variable speed Bosch jig saw motor. It is 120v 5a. I would like to install a pot to keep the variable speed, but don’t know how to wire it. Any suggestions?


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## matthewsx (Dec 29, 2019)

Is it the same spec as the one removed?


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## matthewsx (Dec 29, 2019)

If it’s a “universal” motor you can use one of the variable speed router controllers from Harbor Freight or similar. It will just plug between the outlet and your tool. I don’t see a spec for the potentiometer in your picture but if you got it from an audio application it’s unlikely you’ll be able to use it as is.

john


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## Ulma Doctor (Dec 29, 2019)

you will need more than just a potentiometer and a switch
you can make a PWM driver or purchase one in the form of a router speed control

potentiometers are simply just variable resistors, they don't contain any special powers or mystery components
hooking a potentiometer to the motor alone will not have the desired effect of speed control


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## Latinrascalrg1 (Dec 29, 2019)

So Im sure of what we are speaking of, You are repurposing a hand hand portable 120v power drill motor which is the left side portion of your device in the picture, is this correct?


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## bill stupak (Dec 29, 2019)

Latinrascalrg1 said:


> So Im sure of what we are speaking of, You are repurposing a hand hand portable 120v power drill motor which is the left side portion of your device in the picture, is this correct?


Yes, I am powering a small tool bit grinder, the original jigsaw variable speed was controlled by the trigger switch, which I assumed was just a pot. The pot I have doesn't have any specs printed on it. The rocker switch shown will be the on/off control.


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## Bi11Hudson (Dec 29, 2019)

There's a *long* learning curve involved here. Like posted above, the best bet is to acquire a router speed control and wire that directly in. Another possibility is a light dinner, although that wouldn't last very long because of the load on the motor causing overheating. 

In any case, the only way to use a "pot"entiometer would be to replace the one in the original trigger and keeping all other components. In that case, you must be careful to use a "linear" taper pot, avoiding at all costs an "audio" taper pot. The audio taper will measure electrically the same as a linear taper. The problem arises when you want control "here", the control is actually "over there" somewhere.

The component you are looking for/into is called a "rheostat". It is similar to a potentioneter electrically, but rated for a *much* higher current, 50:1 or larger. The cost of a rheostat so far exceeds that of a router controller that the router control becomes the only practical option. There are other options but you must watch for full 120 volt operation. Many such controllers are rated for 40 volts or less. And D-C output. Such a controller must be avoided

.


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## tazzat (Dec 29, 2019)

Just use the orginal trigger.. make a fineadjust for it..


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## bill stupak (Dec 29, 2019)

tazzat said:


> Just use the orginal trigger.. make a fineadjust for it..


This is probably what I will do or scrap the variable speed altogether, I don't necessarily need it I just thought it would be nice to have that option. Thanks to all for their input.  Stu


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## Latinrascalrg1 (Dec 29, 2019)

I agree, if possible use the control switch that was connected to it from the factory. You can rig up an adjustable setting to hold a desired speed and still  wire in an on off switch so you have a "Memory switch" that can be turned on/off at a set speed.


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## bill stupak (Dec 29, 2019)

The trigger does have a dial on it to preset the speed, I'll see if I can incorporate it into a box somehow,


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