EM DEVICE Group #4: Kevin Cheng, Dan Long, Kathy Qiu

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 Test Results: Fully Operational Output reversible 2.0 Amp *From Pololu.com *From TI DRV8833 data sheet

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 Original Plan: Parallel Orientation 32 Amps 4 Volts Ohm Equivalent (based off Ohm per solenoid) Pros: Low Input Voltage Cons: Very high current Requires 16 Current Regulators 4V 32A = Current Regulator = H-Bridge/Solenoid

CHALLENGES WITH POWER SUPPLY PART 2 Alternative Plan: Series Orientation 2 Amps 64 Volts 32 Ohm Equivalent Pros: Much lower current Only 1 Current Regulator Cons: High Voltage Input 64V 2A = Current Regulator = H-Bridge/Solenoid

CHALLENGES WITH POWER SUPPLY PART 3 Alternative Plan: Combo Orientation 8 Amps 12 Volts 2 Ohm Equivalent Pros: Uses 4 current regulators. Relatively low current. Cons: Still a higher current than desired. 12V 32A = Current Regulator = H-Bridge/Solenoid

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 V range adjustability. Achieved 15W output. Before Demo, power supply failed!

SOFTWARE PIN-SOLENOID DESIGNATIONS

User controls solenoids with PS/2 keyboard Solenoids in turn direct magnet’s motion SOFTWARE GAME MODE

1 st key specifies which solenoid pair to activate along with polarization 2 nd 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 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 TESTING FOR GAME MODE

Sensor system guides magnet from sensor 1 to sensor 34 SOFTWARE AUTOMATION MODE

SOFTWARE

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 SOFTWARE TESTING FOR AUTOMATION MODE

FRAME DESIGN REQUIREMENTS/VERIFICATIONS Non-magnetic Centered solenoid cores Low friction All verified with machine shop  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 – 10mmCritical 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