convert brushed servo to brushless

[bearcreek]

I want to convert a brushed motor RC servo to brushless, so that I have step control like stepper motors do. I have a 12mm feigao motor that fit the 1.5mm pinion perfectly and it runs fine in one direction with an airplane esc, but it is a little to long to fit the case. I like how the servo arm now moves 0.1 mm per step! If I could find a ~17mm diameter and ~18mm length 1.5mm shaft brushless motor (or something near that) would be great. Would it work fine to connect say 6 general purpose silicon transistors to the 3 leads to drive it? No hall effect position sensors needed to determine direction?

[rich smith]

Plane ESC cannot be used for this. To reverse direction you need a car ESC.

I want to convert a brushed motor RC servo to brushless, so that I have step control like stepper motors do. I have a 12mm feigao motor that fit the 1.5mm pinion perfectly and it runs fine in one direction with an airplane esc, but it is a little to long to fit the case. I like how the servo arm now moves 0.1 mm per step! If I could find a ~17mm diameter and ~18mm length 1.5mm shaft brushless motor (or something near that) would be great. Would it work fine to connect say 6 general purpose silicon transistors to the 3 leads to drive it? No hall effect position sensors needed to determine direction?

[bearcreek]

Yes, I figured that the airplane esc was not suitable, but was just testing with it. Today I pulled a stepper motor out of an old dot-matrix computer printer and have more accurate control than a DC servo motor. The feedback potentiometer is not attached, but that may be beneficial in case the stepper loses a few steps.

[Brandano]

Depending on what sort of power you want to get out of it, you might be able to reuse the stepper driver chip off the same printer. Or rip one off the lens sled controller of an old cdrom drive.

[bearcreek]

Yes, that is what I did. I removed the driver IC from the printer. It is rated 3 amps, which seems to be plenty.