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Group #4:
Kevin Cheng, Dan Long, Kathy Qiu
EM DEVICE
INTRODUCTION
Original idea to explore 3-D motion via EM
forces
 Educational tool for classes/labs
After review, switched to a 2-D programmable
game board
Features a game mode and an automation
mode
OBJECTIVES
Explore applications of EM
Navigate a magnet via user input without
any direct contact
Demonstrate autonomous movement via
feedback control
ORIGINAL DESIGN
MODIFIED DESIGN
BLOCK DIAGRAM
H-BRIDGES
REQUIREMENTS
•H-Bridge switches
polarity when the
direction input switches
•Devices supply a
constant 2.0 A ±5% to
solenoids when switched
on and 0.0 A when
switched off
H-BRIDGE PCB AND SETBACKS
Used Texas Intruments
DRV8833 Dual Motor
Driver
Dual Rated output of
1.0 A
Main Issue:
Not breadboard
compatible
Test Results:
• PCB not
operational
• Output was 0.0A
H-BRIDGE SOLUTION
•Pre-fabricated DRV8833
•One directional input
using inverter
*From TI DRV8833 data sheet
Test Results:
•Fully Operational
•Output reversible 2.0
Amp
*From Pololu.com
POWER SUPPLY
REQUIREMENTS/VERIFICATION
•Power from a 120 VAC 60Hz Wall Outlet is converted to a 5 VDC
±5%.
•Supplies those 5 V at 15W ±5% single channel output.
CHALLENGES WITH POWER SUPPLY PART 1
Pros:
Parallel Orientation
•32 Amps
32A
Original Plan:
Low Input Voltage
4V
•4 Volts
Cons:
•0.125 Ohm Equivalent
(based off 0.862 Ohm
per solenoid)
Very high current
Requires 16 Current
Regulators
= Current Regulator
= H-Bridge/Solenoid
CHALLENGES WITH POWER SUPPLY PART 2
Pros:
Series Orientation
Much lower current
•2 Amps
2A
Alternative Plan:
Only 1 Current
Regulator
64V
•64 Volts
•32 Ohm Equivalent
Cons:
High Voltage Input
= Current Regulator
= H-Bridge/Solenoid
CHALLENGES WITH POWER SUPPLY PART 3
Pros:
Combo Orientation
Uses 4 current
regulators.
•8 Amps
32A
Alternative Plan:
12V
Relatively low current.
•12 Volts
•2 Ohm Equivalent
Cons:
= Current Regulator
= H-Bridge/Solenoid
Still a higher current
than desired.
POWER SUPPLY SOLUTION
Breakthrough with H-Bridges:
DRV8833 uses 5V, 3mA supply input to produce a regulated 2.0 A
output
Importance:
•Significantly less amperage needed to supply solenoids.
•3 Amp power supply chosen
POWER SUPPLY TESTING
Results:
•Initially achieved a 5V output.
•4.2-5.2V range adjustability.
•Achieved 15W output.
Before Demo, power supply failed!
SOFTWARE
PIN-SOLENOID DESIGNATIONS
SOFTWARE
GAME MODE
User controls solenoids with PS/2 keyboard
Solenoids in turn direct magnet’s motion
SOFTWARE
GAME MODE
1st key specifies which solenoid pair to activate along with
polarization
2nd key specifies level of strength
Example: User presses “1,” followed by “f”
• Solenoid pair A-L activates with low polarization (i.e. so
that magnet is pushed left) at 50% duty cycle
SOFTWARE
TESTING FOR GAME MODE
Set up grid of 16 LEDs in layout of solenoids
Use 8 additional LEDs for polarization
Successfully verified that keyboard correctly interfaces with Arduino
• User can specify what solenoid LEDs to activate and their
brightness level
• Polarization LEDs turn on/off appropriately
SOFTWARE
AUTOMATION MODE
Sensor system guides
magnet from sensor 1 to
sensor 34
SOFTWARE
SOFTWARE
TESTING FOR AUTOMATION MODE
When magnet was placed in area without sensor, LEDs
behaved correctly
LEDs didn’t respond to sensors
Poor choice of testing
• Unclear if there’s bug in code, muxes, or sensor system
• Alternative verification procedure: hard-code sensors
FRAME DESIGN
REQUIREMENTS/VERIFICATIONS
Non-magnetic
Centered solenoid cores
Low friction
All verified with machine shop
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Aluminum frame
Brass Screws
Delrin plate
Acrylic Roof
FRAME DESIGN
Final build
FRAME DESIGN
CHALLENGE: MAGNET ORIENTATION
Solenoids align magnet side-side
Sensors only detect along single axis (up-down)
SOLENOIDS
REQUIREMENTS/VERIFICATION
Pull magnet across 5cm distance using 2A
 Using power supply, can magnet “fly” to core center
 After testing: Safe up to 3A
Dimensions can fit four solenoids across 10cm(~4 inches)
 Build with Machine Shop and test
Final solenoid (1.00”, 5.0cm)
SOLENOIDS
FUNCTIONAL TEST
Zinc core of threaded rod, washers, and nuts.
1.25” length, 1.5” diameter, ~250 turns
Distance results
Test solenoid setup
SENSORS
Requirements: Locate specific position of magnet
 Use triangulating algorithm
Allegro A1301
 Quiescent at half Voltage (2.5 V)
 Changes from 0-5V depending on polarity (negative-positive)
 Sensing only along a single axis (and single side)
 Triangulating not possible, Had to increase number of sensors
 Cheapest option that is non-latching
SENSORS
Distance graphs
Critical point – 10mm
Critical point – 4mm
SENSORS
CHALLENGE: MUX IMPLEMENTATION
Benefit: Allow for higher sensor resolution
40 Sensors instead of 20
Failed test – Possible reasons
Arduino was not outputting correct select bits
Power supply could not power all devices
Sensors were not properly soldered
SENSORS
RECOMMENDATIONS FOR FURTHER WORK
Integrate Mux/Sensor board with Arduino
Test sensors with solenoids
Reduce friction from magnet on board
Future work: Integrate entire design into a single,
aesthetic unit
SPECIAL THANKS TO
Steve Hall
Iain Brearton
Skee Aldrich - Machine Shop
Mark Smart - Electronics Shop
QUESTIONS