EECS 373 Presentation DC motor with H-bridge Team: Bowen Xu, Chenyu Yi, Yitian Chen 1.

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EECS 373 PresentationDC motor with H-bridge

Team: Bowen Xu, Chenyu Yi, Yitian Chen

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How to drive a motor

• Two functions– Rotate reversely by reverse the voltage (Appendix I)– Speed increases with voltage applied

• LEGO 2838, without load:

M+ -

http://www.philohome.com/motors/motorcomp.htm

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All in one – H bridge

• Integrating the following functions:– Capable of driving the motor in both directions

(Appendix II)– Control the speed (explain later)

• What’s more? – Brake(Appendix III)– Free wheeling(Appendix IV)

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Control the speed using PWM

• Can we use analog?– …Yes… But too complex– We prefer digital (Appendix V)

• Can we connect PWM output pins on MCU with motor?– No!– The motor won’t move– Or magic smoke comes out!

• PWM signal acts as “switch manager”(Appendix VI)– Manage big voltage source with small voltage source– Get different AVERAGE voltage with different duty cycle

R

A safer way to manage the “switches”

5

MVpwr

GND

R

PWM1

PWM2

OUT1

OUT2

6

R

MVpwr

GND

R

PWM1

PWM2

OUT1

OUT2

Vavg GND

0

0

1

Forward

1

3.3V

0V

3.3V

0V

Vavg

GND

77

R

7

MVpwr

GND

R

PWM1

PWM2

OUT1

OUT2

VavgGND

1

1

0

Reverse

0

3.3V

0V

3.3V

0V

GND

Vavg

8

R

8

MVpwr

GND

R

PWM1

PWM2

OUT1

OUT2

GND

1

0

1

Brake 1

0

GND

3.3V

0V

3.3V

0V

GND

GND

99

R

9

MVpwr

GND

R

PWM1

PWM2

OUT1

OUT2

Vpwr

0

1

0

Brake 2

1

Vpwr

3.3V

0V

3.3V

0V

Vpwr

Vpwr

10

MVpwr

GND

R

PWM1

PWM2

OUT1

OUT2

EN

Add one more function: ENABLE

11

PWM1

PWM2

Vpwr

GND

OUT1

OUT2

ENABLE

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Our Basic H-bridge Chip

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LEARN TO USE MC33886An example of using data sheet

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Before we start

• Scenario– Use RS-540 to drive a model car– The rated voltage: 7.2V– Current for normal speed: 3A

• 2 Problems– Is MC33886 capable?• Bear 7.2V?• Supply sufficient current?

– How to connect the pins

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For problem 1: Properties of MC33886

• Output voltage and current:– Vpwr: 5 to 12V– Max current: 5.2A

• Other information– PWM input frequency no higher than 10kHz

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PWM1

PWM2

Vpwr

GND

OUT1

OUT2ENABLE

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For problem 2: Pin descriptions

General Chip we have MC33886(get from data sheet)

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RS-540

7.2V

MCU

PWM1PWM2

01

GNDCcp

D2D1IN2IN1

FS

OUT1

OUT2

Vpwr

30nF

Connect MC33886 with MCU and motor

RS-540MCU

PWM1PWM2

01

GNDCcp

D2D1IN2IN1

FS

OUT1

OUT2

Vpwr7.2V

GNDCcp

D2D1IN2IN1

FS

OUT1

OUT2

VpwrDual H-bridge

to get greater power!

6.03 dollar each(www.findchips.com)

5.2A

5.2A

10.4A

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Questions?

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Appendix IForward and reverse

+ -

+ -M+ - M+ -

+-

+-

Back

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Appendix IIForward and reverse with simple H-bridge

-+

sw1

sw2

sw3

sw4

M+ -

+

-

- +

Back

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Appendix IIIBrake with simple H-bridge

GND+

sw1

sw2

sw3

sw4

M+ -

+

-

GND +

Back

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-+

sw1

sw2

sw3

sw4

M+ -

+

-

BackAppendix III

Brake with simple H-bridge

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+

sw1

sw2

sw3

sw4

M+ -

+

-

+

BackAppendix III

Brake with simple H-bridge

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Appendix IVFree wheeling

Back

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Appendix V PWM and Vavg

3.3V

0V

Vavg = Vpeak * Duty_cycle

Back

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Appendix VIOutput voltage with PWM control

Vpwr = 12V

Vout3.3V

Back

3.6V

Duty cycle: 30%

12V

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Appendix VIIMC33886 Data sheet:

Back

http://www.freescale.com/files/analog/doc/data_sheet/MC33886.pdf

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Appendix VIIIMC33886 Data sheet, pin descriptions

Back

http://www.freescale.com/files/analog/doc/data_sheet/MC33886.pdf