Transcript DC Motor and H Bridge

DC
otor & H Bridge
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Outline
DC Motor
H Bridge
Principle
Control
Speed Control
Power
Figure 1. Real DC Motors
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Principle Recap
•
Figure 2. Lorentz Force Direction
http://hyperphysics.phyastr.gsu.edu/hbase/magnetic/magmom.html
Figure 3. Loop Current Diagram
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Rotational Speed
Assume it is a 6V motor
+
6V
-
Figure 5. Macro View
+
6V
-
Figure 4. Voltage and Full Speed Rotation
commons.wikimedia.org
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Rotational Speed
Assume it is a 6V motor
-
6V
+
Figure 5. Macro View
-
6V
+
Figure 4. Reverse Voltage and Rotation
commons.wikimedia.org
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Rotational Speed
Assume it is a 6V motor
-
4V
+
Figure 5. Macro View
-
4V
+
Figure 4. Small Voltage and Slow Rotation
commons.wikimedia.org
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Speed Control
PWM
% Duty Cycle
↓↓
% AVG Voltage
↓↓
% Speed
http://forum.xda-developers.com/showthread.php?t=2542054
Figure 6. PWM Timing Diagram
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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?
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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)
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H Bridge
Figure 7. An H Bridge Diagram
Table 2. H Bridge Functions
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H Bridge
Figure 7. An H Bridge Diagram
Table 2. H Bridge Functions
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H Bridge
Figure 7. An H Bridge Diagram
Table 2. H Bridge Functions
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H Bridge
Figure 7. An H Bridge Diagram
Table 2. H Bridge Functions
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H Bridge
Figure 7. An H Bridge Diagram
Table 2. H Bridge Functions
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H Bridge
Figure 7. An H Bridge Diagram
Table 2. H Bridge Functions
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H Bridge
Figure 7. An H Bridge Diagram
Table 2. H Bridge Functions
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H Bridge
Figure 7. An H Bridge Diagram
Table 2. H Bridge Functions
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L298N Block Diagram
Figure 8. L298N Block Diagram (L298N Datasheet)
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L298N Block Diagram (Left Half)
Figure 9. L298N Block Diagram (Left Half) (L298N Datasheet)
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Four Switches in H Bridge
Figure 9. L298N Block Diagram (Left Half) (L298N Datasheet)
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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)
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Power Supply
Figure 7. H Bridge Diagram
(http://en.wikipedia.org/wiki/H_bridge)
Figure 9. L298N Block Diagram (Left Half) (L298N Datasheet)
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Logic Power
Supply
Figure 7. H Bridge Diagram
(http://en.wikipedia.org/wiki/H_bridge)
Figure 9. L298N Block Diagram (Left Half) (L298N Datasheet)
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Inputs and Enable
Figure 7. H Bridge Diagram
(http://en.wikipedia.org/wiki/H_bridge)
Figure 9. L298N Block Diagram (Left Half) (L298N Datasheet)
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M
Outputs
Figure 7. H Bridge Diagram
(http://en.wikipedia.org/wiki/H_bridge)
Figure 9. L298N Block Diagram (Left Half) (L298N Datasheet)
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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)
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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)
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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)
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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)
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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)
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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)
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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)
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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)
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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
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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!
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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
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Power Constraint (SN754410)
http://www.ti.com/lit/ds/symlink/sn754410.pdf
Table 4. Voltage Constraint for SN754410
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What if we want to use that large-power DC motor?
Build an H-bridge with 4 switches!
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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
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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
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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
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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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