Interfacing of stepper motor and program point of view understanding

  • Interfacing of stepper motor is not done by L293D or direct connection with MCU(micro controller unit) because problem is same as less current, less voltage and back EMF.
  • And the major problem is sharp cut off in power to the motor as the motor rotates in steps.
  • This points overcome by ULN2803 (18 pin ) IC.

 

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  • Single ULN2803 IC can drive two 4 phase stepper motor.
  • Free willing diodes are used to bypass the back current and protect microcontroller from damage.

 

How stepper motor works?

 

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  • As you can see on above figures, there are 4 wires which provide supply to the motor’s different pole or phase. This is 4 phase stepper motor understanding.
  • In fig1, we give Logic ‘1’ to 2b pin only and rest is at Logic ‘0’. In this case, coil of that supplied pole is energies and attract the rotor as you can see.
  •  In fig2, we give Logic ‘1’ to 2a pin only and rest is at Logic ‘0’. In this case, coil of that supplied pole is energies and attract the rotor as in different direction as it was.
  • Thus, we can rotate stepper motor in desired direction as we want by supplying voltage to particular phase or pole.
  • In these cases, angle of rotation is 90 degree and it is decided by 360/no of pole (coil).
  • As the number of coil increase we get more degree of freedom.
  • We can also make this circuit as 45 degree rotation by applying current to two pole at a time.