Wireless Bluetooth Controller For DC Motor

Introduction Wireless becoming more and more available and widely used Bluetooth is one of the major players Interested in power and motor control Motivation:

Objectives Wireless Controller for DC Motor Bluetooth Wireless Standard Windows based GUI 12 V Permanent Magnet Geared Motor Battery powered Variable speed Features:

Objectives Practical Provides Flexibility Economical User-friendly Can be ran from any PC running Windows Benefits:

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

Bluetooth Bluetooth USB Receiver for PC Set up as COM port Transmits USART serial data to WML- C40 Bluetooth Module PC Side:

Bluetooth BlueSMIRF WML-C40 Module Vcc = 5 V, with internal regulator Receives USART serial data from USB module Transmits to PIC16F877 via serial TX Motor Side:

Microcontroller PIC16F 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 GM 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 2 RPM: Duty cycle = 108 RPM: Duty cycle = 950 Y = mx + b  Duty = 7.92(speed)

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 Operations Max Load Motor Current vs. Terminal Voltage Recommended Max H-Bridge Current = 1.2 A

Results Motor ran in both directions 0-95 RPM on lower geared side RPM on load side Maximum continuous load = 15 W Maximum continuous torque = 1.33 N-m

Results

Duty Cycle to H-Bridge PIC To H-Bridge Control 48 RPM PIC To H-Bridge Control 5 RPM

Motor Duty Cycle Motor 48 RPM Motor 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

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