Remote Unipolar Stepper Motor Controller with 89C51

This is the third and most amazing application of multichannel IR remote where 4 different channels of remote are utilized to control all the parameters of unipolar stepper motor. All three parameters of stepper motor RPM, direction & no. of revolutions can be changed from remote. 89C51 takes care of all the controlling actions.

If you have a stepper motor without any specification the please go through this link. it deals with the procedure to find out the type of stepper motor, its terminals, its coil sequence, step resolution and everything you want.

The project is based on stepper motor control and I have experimented with unipolar stepper motor. One must know first how this stepper motor is controlled. How it can be rotated, how RPM, direction & no. of revolutions can be changed etc. So let us first go through the theory of unipolar stepper motor

Unipolar stepper motor:-

Fig. 1: Image showing Circuit of Unipolar Stepper Motor

In unipolar motor there are four coils. One ends of each coil are tied together and it gives common terminal which is always connected with positive terminal of supply. The other ends of each coil are given for interface. Again here also specific color code is given. Orange is for first coil (L1), brown for second (L2), yellow for third (L3), black for fourth (L4) and red for common terminal.

By means of controlling a stepper motor operation we can

# Increase or decrease the RPM (speed) of it

# Increase or decrease number of rotation of it

# Change its direction means rotate it clockwise or anticlockwise

To vary the RPM of motor we have to vary the PRF (Pulse Repetition Frequency). Number of applied pulses will vary number of rotations and last to change direction we have to change pulse sequence.

So, all the three things depend on applied pulses. Now there are three different modes to rotate this motor

1) Single coil excitation

2) Double coil excitation

3) Half step excitation

The table given below will give you the complete idea that how to give pulses in each mode

Single coil excitation		Double coil excitation		Half step excitation
Clockwise	Anticlockwise	Clockwise	Anticlockwise	Clockwise	Anticlockwise
0001	0001	0011	0011	0001	0001
0010	1000	0110	1001	0011	0011
0100	0100	1100	1100	0010	1000
1000	0010	1001	0110	0110	1001
				0100	0100
				1100	1100
				1000	0010
				1001	0110

(Note:-In half step excitation mode motor will rotate at half the specified given step resolution. Means if step resolution is 1.8 degree then in this mode it will be 0.9 degree. Step resolution means on receiving on 1 pulse motor will rotate that much degree. If step resolution is 1.8 degree then it will take 200 pulses for motor to compete 1 revolution (360 degree))

Now let me give you the specification of the stepper motor that I have used

Max rated voltage: – 5 V

Max rated current per coil: – 0.5 Amp

Step resolution:- 1.8 degree

Max RPM: – 30

Torque: – 1.5 Kg/cm2

After going through all these let us see how 89C51 can control its all three parameters.

Transmitter

Transmitter:-

Again here the 4 channel IR remote (made using 556) is used and its 4 different channels (switches) are assigned 4 different tasks.

Switch	Function
S1	Start rotating motor in clockwise direction
S2	Start rotating motor in anticlockwise direction
S3	Increase RPM by 5 (5, 10, 15,….)
S4	Increase No. of rotations by one

89C51 based 4-pol stepper motor driver:-

The figure given below shows an arrangement for the circuit

Fig. 2: Image showing arrangement of Circuit for 89C51 based 4-pol stepper motor driver

Connection: – just slight modification to last project; all four coils of stepper motor are connected with port P2 pins through current amplifier IC UNL 2003. Port pins P2.0 through P2.3 will generate desire pulse sequence as per above table (you can choose any of the three modes) to rotate motor either clockwise or anti clockwise. It will also vary the PRF to change the RPM. These pulses will be given to UNL 2003. UNL 2003 will provide sufficient current to motor coils.

Operation: – First time when you press switch S1 or S2 (or after micro-controller is reset) motor will start rotating at default RPM of 60 (1 revolution in 1 sec.) for only one rotation. Then after by pressing switch S3 or S4 you can increment RPM or number of rotations. You can only increment these two factors not decrement it because no more switches. If you want to add these functions also then you have to add two more switches for decrementing RPM and no. of rotation. Every time when you press S1/S2 89C51 will rotate the motor at selected RPM till desired number of rotations are completed.

All four LEDs will indicate particular event has happened as given in table below.

LED	Event
Red	will frequently blink at a rate of PRF applied to motor when it is rotating in clockwise direction
Green	will frequently blink at a rate of PRF applied to motor when it is rotating in anticlockwise direction
Yellow	every time will blink once when there is increment in RPM by 5 stays on when Max. limit (30 RPM is reached )
Blue	every time will blink once when there is increment in No. of rotation by 1