DC MOTOR CONTROL
MADE EASY
INTRODUCTION
Often, people attempt to control DC motors with a variable resistor or variable
resistor connected to a transistor. While the latter approach works well, it
generates heat and hence wastes power. A simple pulse width modulation
controller will eliminates these problems. It controls the motor speed by
driving the motor with short pulses. These pulses vary in duration to change the
speed of the motor. The longer the pulses, the faster the motor turns, and vice
versa.
We will be using the Texas Instrument SN754410 to Interface the DC motor
with the FPGA. The Texas Intrument SN754410 was choosen because of its
availablity and because of its many features.
Features of the Texas
Intrument SN754410
- 1-A Output-Current Capability Per Driver
- Applications Include Half-H and Full-H Solenoid Drivers and Motor Drivers
- Designed for Positive-Supply Applications
- Wide Supply-Voltage Range of 4.5 V to 36 V
- TTL- and CMOS-Compatible High-Impedance Diode-Clamped Inputs
- Separate Input-Logic Supply
- Thermal Shutdown
- Internal ESD Protection
- Input Hysteresis Improves Noise Immunity
- 3-State Outputs
- Minimized Power Dissipation
- Sink/Source Interlock Circuitry Prevents Simultaneous Conduction
- No Output Glitch During Power Up or Power Down
- Improved Functional Replacement for the SGS L293
Figure 1 - Schematic of DC Motor Interface (Click to
enlarge)
Table 1: Truth Table of Motor Function
| PWM |
1A |
2A |
Motor Function |
| 0 |
- |
- |
Coast |
| 1 |
0 |
0 |
Dynamic Breaking |
| 1 |
1 |
1 |
Dynamic Breaking |
| 1 |
1 |
0 |
Motor Forward |
| 1 |
0 |
1 |
Motor Reverse |
To make the DC motor to spin in "Forward" direction you would have to make
input 1A high and input 2A low. To "Reverse" direction just set input 1A
low and input 2A high. Also for dynamic braking just set inputs 1A and 2A
to the same value i.e both high. Refer to Table 1 for a summary.
Group Members:
Darren Gonek
Guillermo Barreiro
Andrew Ling
Shyam Chadha
Timmy Li
Reid Orsten
Group AppNotes
TTL
to Serial
DC
Motor Control
CodeWarrior
Tutorial
Surviving VI
RS232 Protocol
RS232
Software Support
References:
Texas Instrument SN754410 Spec Sheet
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