1. Motors & Motor Drivers
ECE 450

2. AC or DC Motors AC DC Few robots use AC except in factories
Most of those that use AC first convert to DC DC
Dominates in robotics
Must be bidirectional

3. DC Motor Types Continuous-duty (run continuously when power supplied)
Brushed
Brushless
Servo
Intermittent-duty (power must be pulsed to run continuously)
Stepper Motors

4. Motor Specifications Operating voltage Current draw Speed Torque
Stalling or Running Torque

5. DC Motor: Brush Motors
The most common. Toys, battery powered tools, electric machines.
Stator (permanent magnets)
Brushes

6. Brush DC Motors Identify: Stator Rotor Brushes Commentator

7. Brush DC Motor How does it work?

8. Pulse Width Modulation
(PWM)
Centered PWM

9. Brushless DC Motor Identify: Permanent Magnets Rotor Brushes
Commentator

10. Brushless DC Motor Housing Laminated steel stack Winding
Permanent magnet
Shaft
Ball bearing 1 2 3 4 5 6
Less common. Higher efficiency, less friction, less electrical noise. Requires electronic driver.

11. Brushless DC Motor How does it work?

12. DC Servo Motor A DC Servo Motor is a DC Motor with
Gears and Electronics with limited
angular rotation (typically 90, 180 or 360º)
Why the addition of gears?
Nylon
Karbonite
Metal
Why electronics?
Digital
Analog

13. Requires constant pulsing ( 50 times / second)
DC Servo Motor
2.00 ms
1.50 ms
1.00 ms
0.50 ms
0.00 ms 1
1.50 ms: Neutral
1.00 ms: 0 degrees
2.00 ms: 180 degrees
Requires constant pulsing ( 50 times / second)

14. Stepper Motor Full Step Half Step
Very common. Required driver. Very strong, when not rotating. Easy to control rotor position.
Full Step
Half Step

15. Full-Step Stepper Motor1 1 1 1

16. Half-Step Stepper Motor1 1 1 1 1

17. Motor Drivers Simple, 1- dc motor (brushes), on/off driver
DC Brush D1
1N5817
(Schottky) M C Q1
2222A
(NPN) B
On: to +9 V
Off: to GND or disconnected R1
1 k E

18. Transistors PNP Bipolar Transistor NPN Bipolar Transistor C B E C B E

19. Motor Drivers Simple, 1-motor, on/off driver
1 k E Q2
2907A
(PNP)
On: to GND or disconnected
Off: to +9 V B C M1
DC Brush M D1
1N5817
(Schottky)

20. Motor Drivers Classic Bipolar H-Bridge
1N5817
(Schottky) M M1
DC Brush
+9 V Q2
2907A
(PNP) R2
1 k B C E R1 D2 Q1
2222A
(NPN) Q4 R4 R3 Q3 D3 D4
On: to +9 V
Off: to GND or disconnected
On: to GND or disconnected
Off: to +9 V
Taken from Intermediate Robot Building by David Cook

21. Motor Drivers Classic Bipolar H-Bridge
1 k E R2
1 k D4
1N5817
(Schottky) D2
1N5817
(Schottky) E B B Q4
2907A
(PNP) C C
from microcontroller
4427 1 2 3 4 8 7 6 5 NC
GND
IN A
IN B
VDD
OUT A
OUT B Q2
2907A
(PNP) M
GND Q3
2222A
(NPN) Q1
2222A
(NPN)
from microcontroller M1
DC Brush R3
1 k C D1
1N5817
(Schottky) C R1
1 k D3
1N5817
(Schottky) B B E E
Taken from Intermediate Robot Building by David Cook

22. Motor Drivers Typical H-Bridge Motor Driver
DC Brush
OUT B
+5 VDC
Disconnected or
from microcontroller
From microcontroller
SN754410 1 2 3 4
ENABLE A&B
OUTPUT A
INPUT A
GND 5 6 7 8
INPUT B
OUTPUT B
VMOTOR
VLOGIC
OUTPUT C
INPUT C
INPUT D
OUTPUT D
ENABLE C&D 16 15 14 13 12 11 10 9
from microcontroller M2
0.1 F
220 F
+4.5 to +36 VDC
Taken from Intermediate Robot Building by David Cook

23. H-Bridge Lab Components
Construct the H-Bridge as shown using components from your Robotics Kit.
Identify those configurations that short circuit the H-Bridge and on the enclosed table enter “Short Circuit” under the Results column
Show this table to either the Instructor or the TA before proceeding any further.
Using your H-Bridge, determine how the motor performs under each of the 16 different combinations of the four transistors
DO NOT verify the short circuit combinations identified earlier!
Pay attention to the transistor numbering in the table compared to the schematic.
Be sure to identify whether or not the motor turns clockwise or counterclockwise
For any breaking actions, identify which direction the motor is turning when breaking occurs. (In some configurations, breaking only occurs when the motor is turning in one direction but not the other.)
Lab Report
To drive larger motors, an H-Bridge with higher capacity currents would be required. Using the components in this lab, determine the component(s) that limit the current for driving a dc motor. Describe your analysis and results in your lab report.
Include the table showing your results for the 16 different combinations for powering the H-Bridge.

24. Motor Drivers Classic Bipolar H-Bridge
1N5817
(Schottky) M M1
DC Brush
+9 V Q2
2907A
(PNP) R2
1 k B C E R1 D2 Q1
2222A
(NPN) Q4 R4 R3 Q3 D3 D4
On: to +9 V
Off: to GND or disconnected
On: to GND or disconnected
Off: to +9 V
Taken from Intermediate Robot Building by David Cook

25. H-Bridge Test Results