Transcript presentation

High Performance Low Cost
Low Lost Wireless DC Motor
Speed Control
Jing Guo & Yu Qiao
TA: Jim Kolodziej
Professor: Paul Carney
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Product Features
• Wirelessly controlled
• Five basic operations: start, stop,
accelerate, decelerate, reset
• 90% efficiency with normal load
• High tolerance in overload
conditions
• Low cost (under $12)
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Main Components
• Control signal generating logic
• Wireless transceiver with encoder
and decoder
• Microcontroller for PWM
generation and overload detection
• Low side gate driver
• Buck converter
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Operation of the Product
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Control Signal Generator
• Five push buttons for five commands with a
3-input NAND gate
Commands
Codes
Start
110
Stop
111
Accelerate
100
Decelerate
010
Reset
001
• A 3-LED array is used to test the output of the
circuit.
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Encoder & Decoder
• Forward and backward parallel to
serial transformation
• Testing: Connect the signal
generator, encoder and decoder in
cascade and test if the output
from LED is consistent.
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Wireless Transmitter & Receiver
• Operating frequency: 315 MHz
• Serial data output from decoder directly feed
into TX module
• Digital modulate and send to antenna
• RX module demodulates and amplifies the
signal picked up by antenna
• Serial data output to decoder
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Testing
• Test with 1kHz square wave from
function generator (waveform got
duplicated at RX end)
• Test with the designed circuit (the
LED array at RX gives correct
combination)
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Micro-controller Unit
MSP430G2152
• PWM Generation
• Feedback Unit
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PWM Generation
MSP430G2152
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Testing
Connect the Control Signal Generator
to
the
selected
input
and
the
generated waveform has the correct
the frequency and changes according
to the command signals
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Low Side Gate Driver
The low side gate driver take the PWM
signal as its input and then boost the
voltage to 10V
Testing: Connect the 3V PWM signal to
the input and check if the output
waveform has the same shape but swings
between 0 and 10V
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Buck Converter
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Testing
Connect the PWM signal from the
function generator to the gate of the
MOSFET. Changing the duty ratio of the
PWM will change the speed of the
motor correspondingly.
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Feedback Unit
• Voltage Detector
• Numerical Integral Approximation
• Overload Signal Generation
(detect signal and shut down
signal)
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Control Unit Structure
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Numerical Integral Approximation
•
•
The average detect voltage over 100 time periods is over
V_normal, then overload is detected.
If overload for 192000 time periods, output an OFF signal to
PWM generator until the RESET signal is sent by the user
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Overload Circuit Protection Function
Two frequency modes
High (160 kHz): for normal operation
Low (1.6 kHz): for overload protection
Note: Switching from Low to High requires
RESET command from the user
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Normal Load Setup
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Normal Load Efficiency
Temperature
Around 34 ℃
Input Power = 12.1V *12.41A = 150.04 W
Output Power = 10.4V * 14.0A = 145.6 W
Efficiency = 145.6W /150.04W = 97%
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250W Overloading Setup
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250W Overloading without Protection
Temperature
Around 91 ℃
Input Power = 11.97V *21.3A = 254.96W
Output Power = 10.1V * 22.9A = 231.29 W
Efficiency = 231.29W /254.96W = 90.7%
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250W Overloading with Protection
Temperature
Around 31 ℃
Input Power = 11.97V *21.5A = 257.35 W
Output Power = 12.8V * 16.8A = 215.04 W
Efficiency = 215.04W /257.35W = 83.5%
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Cost
• Total cost for the motor speed
control parts = $10.602
• Total cost for the wireless
connection parts = $55.44
• Total cost for the entire project =
$66.442
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Challenge
• Properly detect and respond to
overloading
• Handle high current test cases (up
to 50 A)
• Cost limitation ($12 per unit)
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Success
• Transmitting and receiving control
signals wirelessly
• Successfully protecting the circuit by
lowering frequency
• Properly setup shut down point to
protect the motor
• Keeping the cost low
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Future
• Applications
- Shopping cart
- Golf bag carrier
• Solid competitiveness on markets
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Credits
Professor Philip T. Krein
Power lab administrator: Kevin James
Colravy
TA: James Kolodziej
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