MOTION CONTROL
------------------------

control current for smoother motion



STEPPERS
------------------------

4 coils in the perifery
6 permanent magnets in the core

COLORS:
red,green -> supply voltage
brown     -> logic
black     -> logic     
yellow     -> logic
orange     -> logic

   
         N        
      ~~~~~~~    

         S       
                   
     N       N     
         O         
     S       S  
                
         N       
                
      ~~~~~~~
         S
       
can't use the steps for absolute positionning.. (can miss steps, or go over)
need some feedback loop for precise control

unipolar vs bipolar

  bipolar -> twice the torque, but twice the FETs

                  O
                  |
           --------------
          |              |
         -                - 
  PFET-||                  ||-PFET 
         -                -
          |              |
          |~~~~~~~~~~~~~~|
          |              |
         -                -              
  NFET-||                  ||-NFET 
         -                -
          |              |
           --------------  
                  |
                -----
                 ---
                  -
  

  unipolar -> half the torque, but half the FETs
  
                  O
                  |
          |~~~~~~~|~~~~~~| 
          |              |
         -                -              
  NFET-||                  ||-NFET 
         -                -
          |               |
           ---------------   
                  |
                -----
                 ---
                  -



TRANSISTORS
-------------------------

IGBT - insuleted gate bipolar transistor -> switch high current



MOSFETS - switch with voltage (no waste of current) appears as a switching resistor

N-channel FET sinks current
P-channel FET sources current


      G         gate
    =====
  ---------     oxide
  =       =
  S       D     source -- drain             




BUY MOTORS @ JAMECO

      
http://fab.cba.mit.edu/fab/