Controlling Bipolar Stepper Motor

The application of Stepper Motor covers wide sector of Industry. Stepper is commonly used in position controlling systems.

Bipolar Stepper Motor

It’s consisted of 2 windings (coils). Each end of the coils will be connected by wires to a motor controlling circuit. So, there will be four wires of the output for each Bipolar Stepper Motor.

Picture I. Bipolar Stepper Motor Windings

The Way to Know Which Wires Are Pair

There will be two pairs of wires. We can use ohm-meter to know the pairs of that wires, and I think you have already known how to check it.^_^

After knowing the pairs, you must know how to control the stepper motor, so that it can rotate CW or CCW. Here is the logic of controlling the bipolar stepper motor:

	Time -->
A	1	0	0	0	1	0	0	0	1	0	0	0	and so on
B	0	0	1	0	0	0	1	0	0	0	1	0	and so on
C	0	1	0	0	0	1	0	0	0	1	0	0	and so on
D	0	0	0	1	0	0	0	1	0	0	0	1	and so on

 Tabel I. CW Rotating

	Time -->
A	0	0	0	1	0	0	0	1	0	0	0	1	and so on.
B	0	1	0	0	0	1	0	0	0	1	0	0	and so on.
C	0	0	1	0	0	0	1	0	0	0	1	0	and so on.
D	1	0	0	0	1	0	0	0	1	0	0	0	and so on.

Tabel II. CCW Rotating

 Driver for Bipolar Stepper Motor

As we know that, we cannot control the stepper directly by using microcontroller  (ATMega8535 for example)without any driver. It’s because of the current output of micro is so small. So we use driver for controlling the motor. We can use L293D or L298 as IC Driver. If the stepper motor needs current less then 1A, just use L293D, otherwise use L298.

Here is the schematic using L293D as a driver:

Picture 2. L293D Driver schematic to control Bipolar Stepper Motor

Here is the logic for the driver (both of L293D and L298 are the same) :

EN1	IN1	IN2	OUT1	OUT2	Current Direction
H	L	L	L	L	Stop
H	L	H	L	H	B to A
H	H	L	H	L	A to B
H	H	H	H	H	Stop
L	X	X	X	X	Stop

EN2	IN3	IN4	OUT3	OUT4	Current Direction
H	L	L	L	L	Stop
H	L	H	L	H	D to C
H	H	L	H	L	C to D
H	H	H	H	H	Stop
L	X	X	X	X	Stop

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