Convert Drill Motor to Servo - Possible?

[creative_mind]

I am looking for ideas converting a certain type of drill motor into a servo motor with the added encoder.

Has anyone done this before?

Is it possible to accomplish the task?

I remember a thread here at the zone that someone did it.

What's the difference between drill motor and a servo motor aside the encoder that goes with it?

Thanks.

[kwcurtin]

Great question...

I was pondering the same thing, only for a router motor.

These motors are "universal", meaning that they can operate on AC or DC. However, these have wound fields instead of permanent magnets. A standard servodrive would have a problem with the field winding. As the servodrive changes the voltage to the motor, the field's flux would change as well. This implies that the motor would not exhibit a constant rpm/volt ratio.

I would assume that if you split off the field and excited it separately from a constant current power supply, then you would be able to operate the motor ok with the servodrive. Constant voltage would probably work ok as well. Just make certain that you cut off the servodrive in case the field power fails. If you don't then the motor could overspeed, especially in lightly loaded circumstances.

[balsaman]

They are universal motors but built in such a way that they are optimized for AC. They will work on DC but not for long.

E

[creative_mind]

What about the cordless drill that runs on rechargeable batteries?

It seem to me that the motor is a DC type with using feild magnents.

[jimbo]

I wouldnt bother trying to convert a drill or router or even a cordless drill. THe motors in cordless drills are not that big and rely on bit of gear reduction. I would look for servos on ebay or at the online surplus stores. Have a look at the servos listed in the cheap servos thread. YOu will be so much further ahead, the motor will have a proper faceplates for installing motor and encoders and are optimized to run as a servo, usually with better rotating inertia, torque curves, etc.