Bipolar micro-step driver for stepper motors, DC/AC servo motor drives for reliable motion controllers in CNC machines
Connecting Stepper Motor To Bipolar Micro-Step Driver
1. Unipolar (5, 6 or 8 leads stepper)
There are 2 set of coils inside the stepper motor with one end of each set connected together and taken out (in case of 6 leads) or one end of all four coils connected and taken out (in case of 5 leads). For later the only option is unipolar drivers, these are the simplest, not very efficient drivers and will not provide the maximum torque. Applying current pulses to one coil of each set turn the motor in one direction and similarly energizing other coil will turn the motor in other direction one step.
2. Half Coil wired in bipolar mode( 6 or 8 leads stepper)
Same Voltage & Amperage as unipolar above but only uses one coil per phase.Bipolar driver will energize the coil by sending current in the coil in both directions at any given time, current in one directio move the motor in one direction and turn it backward by reversing the current in same coil, keeping the current same as unicoil but using only one half of coil will reduce the torque to 1/sq-rt(2) or 71% though. Better method for bipolar driving is wiring the coils in series or parallel as below.
3. Bipolar winding in series (6 or 8 wire motor)
Here the 2 coils from respective phases are connected in series (in case of 6 wires they are alreay connected internally and we just don't use the center tap).The driving methods is same as half coil but now the current passes through 2 both coils in single phase thus producing more torque than half coil driven in bipolar mode. Series motors have high inductance so lose torque rapidly as speed increases and will stall at lower speed than half coil or parallel connected (as below).
4. Bipolar winding in parallel (8 wire motors)
Both coils from respective phases are connected in parallel (as we need access to all wires this is only possible in 8 wire motors). The driving method is same as half coil or series connected bipolar but now the current passes through 2 both coils in single phase thus producing more torque than half coil driven in bipolar mode. This method provides usable torque up-to higher RPM and is best way to wire stepper in CNC systems. As a side note, watch out for the heat produced as a result of current flowing through all the coils and be sure to reduce the current and driving voltage (as the induce is significantly less in this case) appropriately.
Only 4 wires on your stepper motor ?
Connecting a 4 wire motor is simple as there are only four leads and it can be only connected with bipolar drive. Be aware though that many of these motor are actually internally connected as series or parallel winding, so always ask the manufacturer for a data-sheet.