DC Motor and H Bridge

Report
DC
otor & H Bridge
1
Outline
DC Motor
H Bridge
Principle
Control
Speed Control
Power
Figure 1. Real DC Motors
2
Principle Recap
•
Figure 2. Lorentz Force Direction
http://hyperphysics.phyastr.gsu.edu/hbase/magnetic/magmom.html
Figure 3. Loop Current Diagram
3
Rotational Speed
Assume it is a 6V motor
+
6V
-
Figure 5. Macro View
+
6V
-
Figure 4. Voltage and Full Speed Rotation
commons.wikimedia.org
4
Rotational Speed
Assume it is a 6V motor
-
6V
+
Figure 5. Macro View
-
6V
+
Figure 4. Reverse Voltage and Rotation
commons.wikimedia.org
5
Rotational Speed
Assume it is a 6V motor
-
4V
+
Figure 5. Macro View
-
4V
+
Figure 4. Small Voltage and Slow Rotation
commons.wikimedia.org
6
Speed Control
PWM
% Duty Cycle
↓↓
% AVG Voltage
↓↓
% Speed
http://forum.xda-developers.com/showthread.php?t=2542054
Figure 6. PWM Timing Diagram
7
But…
Drive?
VCC: ~3.3V
Current: ~10mA
http://www.hennkwell.com.tw/products.php?func=p_detail&p_id=39&pc_parent=8
Table 1. Specification of DC Gear Motor
Backwards?
8
H Bridge
Figure 7. H Bridge Diagram
(http://en.wikipedia.org/wiki/H_bridge)
Table 2. H Bridge Functions
(http://en.wikipedia.org/wiki/H_bridge)
9
H Bridge
Figure 7. An H Bridge Diagram
Table 2. H Bridge Functions
10
H Bridge
Figure 7. An H Bridge Diagram
Table 2. H Bridge Functions
11
H Bridge
Figure 7. An H Bridge Diagram
Table 2. H Bridge Functions
12
H Bridge
Figure 7. An H Bridge Diagram
Table 2. H Bridge Functions
13
H Bridge
Figure 7. An H Bridge Diagram
Table 2. H Bridge Functions
14
H Bridge
Figure 7. An H Bridge Diagram
Table 2. H Bridge Functions
15
H Bridge
Figure 7. An H Bridge Diagram
Table 2. H Bridge Functions
16
H Bridge
Figure 7. An H Bridge Diagram
Table 2. H Bridge Functions
17
L298N Block Diagram
Figure 8. L298N Block Diagram (L298N Datasheet)
18
L298N Block Diagram (Left Half)
Figure 9. L298N Block Diagram (Left Half) (L298N Datasheet)
19
Four Switches in H Bridge
Figure 9. L298N Block Diagram (Left Half) (L298N Datasheet)
20
H Bridge’s Shape
Figure 7. H Bridge Diagram
(http://en.wikipedia.org/wiki/H_bridge)
Figure 9. L298N Block Diagram (Left Half) (L298N Datasheet)
21
Power Supply
Figure 7. H Bridge Diagram
(http://en.wikipedia.org/wiki/H_bridge)
Figure 9. L298N Block Diagram (Left Half) (L298N Datasheet)
22
Logic Power
Supply
Figure 7. H Bridge Diagram
(http://en.wikipedia.org/wiki/H_bridge)
Figure 9. L298N Block Diagram (Left Half) (L298N Datasheet)
23
Inputs and Enable
Figure 7. H Bridge Diagram
(http://en.wikipedia.org/wiki/H_bridge)
Figure 9. L298N Block Diagram (Left Half) (L298N Datasheet)
24
M
Outputs
Figure 7. H Bridge Diagram
(http://en.wikipedia.org/wiki/H_bridge)
Figure 9. L298N Block Diagram (Left Half) (L298N Datasheet)
25
Functions
M
S1
S3
1
S2
S4
0
1
Figure 9. L298N Block Diagram (Left Half) (L298N Datasheet)
Table 2. H Bridge Functions
(http://en.wikipedia.org/wiki/H_bridge)
26
Functions
M
S1
S3
0
S2
S4
1
1
Figure 9. L298N Block Diagram (Left Half) (L298N Datasheet)
Table 2. H Bridge Functions
(http://en.wikipedia.org/wiki/H_bridge)
27
Functions
v
M
S1
S3
X
S2
S4
X
0
Figure 9. L298N Block Diagram (Left Half) (L298N Datasheet)
Table 2. H Bridge Functions
(http://en.wikipedia.org/wiki/H_bridge)
28
Functions
M
S1
S3
0
S2
S4
0
1
Figure 9. L298N Block Diagram (Left Half) (L298N Datasheet)
Table 2. H Bridge Functions
(http://en.wikipedia.org/wiki/H_bridge)
29
Functions
M
S1
S3
1
S2
S4
1
1
Figure 9. L298N Block Diagram (Left Half) (L298N Datasheet)
Table 2. H Bridge Functions
(http://en.wikipedia.org/wiki/H_bridge)
30
Functions
M
S1
S2
S3
S4
Figure 9. L298N Block Diagram (Left Half) (L298N Datasheet)
Table 2. H Bridge Functions
(http://en.wikipedia.org/wiki/H_bridge)
31
Functions
M
S1
S2
S3
S4
Figure 9. L298N Block Diagram (Left Half) (L298N Datasheet)
Table 2. H Bridge Functions
(http://en.wikipedia.org/wiki/H_bridge)
32
Functions
M
S1
S2
S3
S4
Figure 9. L298N Block Diagram (Left Half) (L298N Datasheet)
Table 2. H Bridge Functions
(http://en.wikipedia.org/wiki/H_bridge)
33
An example
40V
http://www.eecs.umich.edu/eecs/courses/eecs373
/labsW14/lab6/index.html
http://www.motioncontroltips.com/2013/05/06/30mm-dcmotor-from-maxon/
Figure 10. 30mm DC Motor from Maxon
Figure 11. SN754410 Pin Connections (SN754410 Datasheet)
Figure 12. SmartFusion FPGA
GND
34
What if we want to use a large-powered motor?
50V
http://www.motioncontroltips.com/2013/05/06/30mm-dc-motor-from-maxon/
Figure 10. 30mm DC motor from maxon
Figure 13. L298N Pin Connections (L298N Datasheet)
It will likely burn the H-bridge!
35
Voltage Constraint (L298N)
https://www.sparkfun.com/datasheets/Robotics/L298_H_Bridge.pdf
Table 3. Voltage Constraint for L298N
• DC voltage cannot exceed H-bridge voltage constraint
36
Power Constraint (SN754410)
http://www.ti.com/lit/ds/symlink/sn754410.pdf
Table 4. Voltage Constraint for SN754410
37
What if we want to use that large-power DC motor?
Build an H-bridge with 4 switches!
38
Which switch shall we use?
• BJT
(Bipolar Junction Transistor)
Easier to build, use less circuitary
Good for low current operation
• MOSFET
(Metal–Oxide–Semiconductor
Field-Effect Transistor)
Good for high current operation
VS
http://www.eeweb.com/electronics-forum/howthis-h-brigde-is-working
Figure 14. H-bridge with BJT
http://www.youtube.com/watch?v=A_JNjAFo1f4&list=PL
XrSeSVAb819HfhysOtYMdwDg3CTKXi6B
Figure 15. H-bridge with MOSFET
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What is
BJT?
What is
MOSFET?
Don’t need to know
http://fourier.eng.hmc.edu/e84/lectures/ch4/node3.html
http://robertdick.org/eecs312/lectures/dic-l5.pdf
PNP – active low
NMOS – active high
NPN – active high
PMOS – active low
Choose voltage/current wisely on gate/base
40
How to use BJT?
C
B
E
http://blog.oscarliang.net/bjt-bipolarjunction-transistor-beginner-tutorial/
Figure 16. BJT Model
http://www.eeweb.com/electronics-forum/howthis-h-brigde-is-working
Figure 17. H-bridge with BJT
41
How to use MOSFET?
PMOS
NMOS
http://airsofttutorials.com/tutorials/diy-mosfet.html
Figure 18. MOSFET Model
http://www.youtube.com/watch?v=A_JNjA
Fo1f4&list=PLXrSeSVAb819HfhysOtYMdwD
g3CTKXi6B
Figure 19. H-bridge with MOSFET
Connect PMOS to Vcc, NMOS to ground
42
Reference
DC Motor:
Basic Principle:
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/motdc.html
http://en.wikipedia.org/wiki/DC_motor
Speed Control with PWM:
http://www.youtube.com/watch?v=NqqgbS3KXz0
Shaft Encoder
https://www.anaheimautomation.com/
manuals/forms/magnetic-encoder-guide.php
H Bridge
http://en.wikipedia.org/wiki/H_bridge
L298N Datasheet:
https://www.sparkfun.com/datasheets/Components/General/L298N.pdf
SN754410 Datasheet:
http://www.ti.com/lit/ds/symlink/sn754410.pdf
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