Hi!
I´v been working on my own CNC mill for a while now.. The mechanical parts are at the stage where I can start building control for my servos.
http://www.saunalahti.fi/~jikuuk/Images/Project/cnc/
(In finnish..)
Most of the parts in my mill, including servos (Dunkermotoren BG63S55) I have found from local junk yard.. So no complete drivers here.
I found these custom made high current drivers along with the servos that seem to work using PWM and direction signals.. But current limit is a bit of a problem. Also, these don´t spin as smooth on low rev as I´s like them to spin.
So, I´v started to do some research on building my own controller cards.
Basic plan is to use a NSC LM629 as the PID processor, and a PIC or an AVR micro to control it.. Or then I make an ISA- bus card and let the computer control the LM629´s directly.
But that high current drive of the brushless motors..
They seem to be two phase motors, two coils like on a bipolar stepping motor + 2 hall- sensors for position feedback. Those two Hall- sensors don´t give enough precision, so I´m wondering wether there might be a chip somewhere that could count the steps from the rotary encoders (Optical, 1000steps/rev) of my motors and use them as reference.
Have you seen such chips?
Or do I have to add another uC to the driver board for the commutation...