Documentation bipolar stepper motor driver circuit
BIPOLAR STEPPER MOTOR DRIVER CIRCUITBSECE 41A1PRESENTED BY: Cauan, Sarah Krystelle P.PRESENTED TO: Engr. Jan Berden D. BermejoDATE: Oct. 12, 2011
ABSTRACT Stepper motors are used in any application which requires a discrete rotationalmovement. The performance of stepper motor is strongly dependent on the driver circuit. Thereare two basic winding arrangements in two phase stepper motor, the unipolar and the bipolar. This project contains the discussion and features of simple bipolar stepper motor driver. Itprovides the forward and reverse control function. The concept of this project got from a simplerunning lights circuit. The circuit contains three different IC which are the LM555, 94LS194, and the L293D.The stepping rate of the stepper motor is controlled by the 1 Megaohm potentiometer while theswitch determined the direction of the motor. The LM555 astable oscillator produces clockpulses that are directed to PIN 11 of the 74194 shift register. Each time the output of the LM555timer goes high, the high state at the pins 12, 13, 14, and 15 of 74194 is shifted either up or downby one place. The output shift determines the direction of the rotation of motor. Switch S1 and S2,which are connected to the switch control the direction. When the S1 is active, the motor willrotate clockwise, on the other hand, when S2 is active, the motor will rotate counter-clockwise.The four outputs of the 74194 are fed to one of the driver segments of a LS293D - H Bridgedriver IC (IC 3). The output will be dependent on the input on LS293D segment.
CIRCUIT DESIGN COMPONENTS1 MΩ Potentiometer The potentiometer controls the rate of the bipolar stepper motor.NE555NOperation of 555 Timer The pin connections are as follows: 1) ground, 2) trigger, 3) output, 4) reset, 5) control, 6)threshold, 7) discharge, and 8) positive supply voltage.
The operation of the 555 timer revolves around the three resistors that form a voltagedivider across the power supply, and the two comparators connected to this voltage divider(See Figure 2). The IC is quiescent so long as the trigger input remains at positive supplyvoltage and the threshold input is at ground. The three resistors in the voltage divider all have the same value, so the comparatorreference voltages are one-third and two-third of the supply voltage, whatever that may be. Thecontrol voltage input at pin 5 can directly affect this relationship. The internal flip-flop changes state when the trigger input at pin 2 is pulled downbelow one-third of positive supply voltage. When this occurs, the output changes state topositive supply voltage and the discharge transistor (pin 7) is turned off. The trigger input cannow return to positive supply voltage; it will not affect the state of the IC. However, if the threshold input (pin 6) is now raised above two-third of positive supplyvoltage, the output will return to ground and the discharge transistor will be turned on again.When the threshold input returns to ground, the IC will remain in this state, which was theoriginal state. (Source: http://www.play-hookey.com/digital/timer_555.html)Operating Modes of 555 Timer There are three operating modes of 555 – monostable, astable, and bistable modes. Amonostable mode circuit produces one pulse of a set length in response to a trigger input. A bistable mode has two stable states, high and low. Taking the Trigger input low makesthe output of the circuit go into the high state. Taking the Reset input low makes the output of thecircuit go into the low state. This type of circuit is ideal for use in an automated model railwaysystem where the train is required to run back and forth over the same piece of track.
The output of astable continually switches between high and low without anyintervention. This type of circuit could be used to give a mechanism intermittent motion byswitching a motor on and off at regular intervals. (Source: http://www.555-timer-circuits.com/operating-modes.html) 10 pF Ceramic Capacitor The 10 pF capacitor is used to reduce the electrical noise with the pin 5 connected toground. DM74LS194N This integrated circuit is used to operate the direction of the bipolar stepper motor. This iscommonly known as 4 Bit Universal Shift Register.