Hi,

I agree with Max, a triac can be used to 'adjust' the speed of the motor but if you want speed 'control' then you need feedback.

Feedback can come in several different forms, as pulses from a light sensor or voltage from a very small generator, but the simplest is to use the back EMF of the motor to control the speed. Using the back EMF you dont need any sensor other than maybe a small value resistor to measure the current in the motor.

I have actually built a couple speed 'adjusters' and 'controllers' in the past, three different types for motors with brushes and two of them were Dremels.
The first used a triac and op amp to control the firing of the triac, for the Dremel.
The second was the same except it had to adjust the speed for a much bigger motor for a big router.
The third type was an actual controller based on back emf used to control the motor in a tape player.

There was a fourth type that had to control an AC motor, that needed to change frequency as well as applied voltage in order to change the speed. That was much more complicated because it had to be a DC to AC converter to start with and then the frequency had to be adjusted as well as the output voltage when the user turned the pot.

They also make routers that are not as big as a regular router but twice the diameter of the usual Dremel tool. These things have quite a bit of power when used with small cutting bits. We used one once to cut a rectangular hole in a door jam for a new lock and it took like 2 minutes to do. The regular Dremel (1 to 1.5 amp motor) would have taken 15 minutes to do that.
These larger routers usually are advertised for cutting sheetrock and often come with a couple cutting bits that look almost like drill bits but with longer flutes.

One caution though is that if you intend to control a Dremel that already has a speed control built in, you should open it up and disable the speed control or remove it entirely before you attempt to use your own triac speed controller. The Dremel with a speed controller already on it requires an AC input not a triac pulsed AC.

 

I done and removed the speed control in the Dremel and put the hot wire from plug in to motor and ground other side motor and plugged in to foot pedal but don't know if that will work

 

Doug, repeating your posts is not helpful.

 

Well how do I apply ac to the Dremel and foot control

 

How do I add ac power to the Dremel or foot pedal