Transcript Wireless Bluetooth Controller For DC Motor

Wireless Bluetooth Controller For
DC Motor
Introduction
Motivation:
Wireless becoming more and more
available and widely used
Bluetooth is one of the major players
Interested in power and motor control
Objectives
Features:
Wireless Controller for DC Motor
Bluetooth Wireless Standard
Windows based GUI
12 V Permanent Magnet Geared Motor
Battery powered
Variable speed
Objectives
Benefits:
Practical
Provides Flexibility
Economical
User-friendly
Can be ran from any PC running
Windows
Applications
Robotics
Remote control car
Industrial Uses
Household Uses
Design Specs
Output voltage varying from 0-12 Vdc
Adjustable speed from 0 to 95 RPM
and 0 to 6222 RPM on load side
Motor can turn in both directions
Continuous motor loads of 15 W
Maximum motor torque of 2.12 N-m
Wireless control up to 60 feet
Block Diagram
Hardware Layout
Full Schematic
User Interface
GUI developed in Visual C++
User can accelerate, decelerate, start
and stop motor
Motor direction can be chosen
Speed referenced to lower geared side
Maximum speed setpoint of 95 RPM
Displays Load side RPM as well
User Interface
Speed is output to serial port by
software
Control signal specifies direction
Transmitted via USB Bluetooth Module
When Stopped, speed is ramped down
Same for direction switch
User Interface
User Interface
Bluetooth
PC Side:
Bluetooth USB Receiver for PC
Set up as COM port
Transmits USART serial data to WMLC40 Bluetooth Module
Bluetooth
Motor Side:
BlueSMIRF WML-C40 Module
Vcc = 5 V, with internal regulator
Receives USART serial data from USB
module
Transmits to PIC16F877 via serial TX
Microcontroller
PIC16F877 40 pin DIP
Programmed in C using CSS Compiler
Receives speed control signal from user
software
Translates desired speed to necessary duty
cycle
16 kHz internal clock used for timers
Sends duty cycle to H-bridge inputs using
onboard PWMs
H-Bridge
NJM2670D2-ND Dual H-Bridge Driver
Consists of 4 MOSFETS as switches
Duty cycle determines speed by controlling
how long switches are active
Motor direction can be controlled
IN1 and IN2 fed from PWM
Adjusted voltage is output to motor terminals
H-Bridge
Image from Wikipedia
Motor
Pittman GM9434 12 V Permanent Magnet DC
Motor
65.5:1 Gear Ratio
Max Rated Motor Speed = 93.9 RPM
Max Rated Torque = 2.12 N-m
Functional Tests
Used HyperTerminal to get initial connection
between Bluetooth Modules and another PC
acting as the PIC
Sent serial input to PIC, tested basic outputs
(LED, serial text echo)
Tested H-Bridge using hardwired controls to
verify functionality
Motor operation verified using battery
Operation Tests
For a given duty cycle, the resulting speed
was measured
Using a collection of these points, a linear
translation from duty cycle to speed was
calculated
@ 2 RPM: Duty cycle = 110
@ 108 RPM: Duty cycle = 950
Y = mx + b  Duty = 7.92(speed) + 94.15
Challenges
Replaced Voltage Divider consisting of
resistors with Voltage Regulators
Original H-Bridge was Surface Mount
Replaced expired Bluetooth module with
simpler model with internal voltage regulation
ASCII Translation Issues
Converting string control signal to usable
decimal integer
Successes
No voltage issues after switching to
regulators
Solved ASCII formatting issues
New H-Bridge was capable
PWM operations didn’t provide difficulties
Motor Operations
No-Load Motor Current vs. Terminal Voltage
Motor Voltage vs. Input Motor Current (No Load)
0.5
0.45
Input Current (A) (A)
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0
0
2
4
6
8
10
Applied DC Motor Voltage (12 V)
12
14
Motor Operations
Max Load Motor Current vs. Terminal Voltage
Motor Voltage vs. Input Motor Current (With Load)
1.4
Input Current (A) (A)
1.2
1
0.8
0.6
0.4
0.2
0
0
2
4
6
8
10
12
14
Applied DC Motor Voltage (12 V)
Recommended Max H-Bridge Current = 1.2 A
Results
Motor ran in both directions
0-95 RPM on lower geared side
0-6222 RPM on load side
Maximum continuous load = 15 W
Maximum continuous torque = 1.33 N-m
Results
DC Motor Efficiency
Efficiency (%) x
100
80
60
40
20
0
0
20
40
60
Motor Speed (RPM)
80
100
120
Duty Cycle to H-Bridge
PIC To H-Bridge Control Signal
@ 48 RPM
PIC To H-Bridge Control Signal
@ 5 RPM
Motor Duty Cycle
Motor Voltage
@ 48 RPM
Motor Voltage
@ 5 RPM
Next Step
Designed feedback loop for closed system
control
Installed Fairchild H21A1 Phototransistor
Optocoupler
Designed optical encoder wheel on motor
shaft with one notch to read RPM
Directed signal to PIC, began programming
Next Step
Next Step
Feed Forward can provide very tight speed
control when load is known
With Feedback implemented, will respond to
change in load and compensate
PDA instead of laptop
Recommendations
Use an H-bridge with high current rating to
maximize power produced
PIC Programming: C over Assembly
Stable Voltage Regulators = Good
Size Motor and components based on power
needs
Thank You
Brian Raczkowski
Alex Spektor
Wally Smith & Frank Dale (Parts Shop)
Scott McDonald (Machine Shop)
Thank You