Senior Experience in Electrical Design

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Jonathan Baisch Brandon Sargent Ryan Shaffer Tim
Stewart Dale Weaver

• Senior Experience in Electrical Design

04.24.08
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Introduction

• Develop a microcontroller-based crane control
  system to simulate hydraulic components.
• Bechtel
• Largest engineering company in the U.S.
• Ryan Muller Dan Roseum Pittsburgh, PA
• Our control system will be used on a machine that
  simulates a real crane.

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Block Diagram
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Specifications

• The system must be microcontroller-based. The
  microcontroller must be able to replicate the
  input/output characteristic supplied to us.
• Code written for the microcontroller must be
  written in C.
• All components on the PCB must be mounted on the
  top of the board, and surface mount devices are
  not to be used.
• External connections from the PCB must be made
  using screw terminal blocks.

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Block Diagram

• We divided our design into five main blocks and
  assigned each to a specific team member.

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Microcontroller Block Diagram
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Code Overview

• Programmed in C
• 251 lines of code

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Analog To Digital Subsystem

• 10-bit digital output
• Provides 0.019 V resolution on the input analog
  voltage
• VRH 5 V VRL 0 V N 10 bits

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A/D Conversion Testing Results
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Microcontroller Function Subsystem

• The two enable inputs serve as a global
  enable/disable for the duty cycle output in each
  direction

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Duty Cycle vs. Input Reference Voltage Graph
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Pulse Width Modulation Subsystem
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Frequency Calculations
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Pittman Motor Performance at Various Frequencies
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Analog Input Circuitry
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Analog Input Circuitry

• Speed reference input to the system ranges
  between -10 V and 10 V
• Microcontrollers A/D converter accepts inputs
  between 0 V and 5 V
• Need to linearly convert input voltage values
  before sending to A/D converter
• We chose to scale the input down to a 1 V to 5 V
  range (this decision will be explained later)

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Analog Input Circuitry
2 op amps, 7 resistors
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Analog Input Circuitry
1 op amp, 4 resistors
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Analog Input Circuitry

• To produce a 4-20 mA output control signal, we
  chose to build a voltage-controlled current
  source (VCCS)
• We chose to scale our input to a 1 V to 5 V range
  because it makes this transition linear

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Analog Input Circuitry
Reference Mazi Hosseini, Electronic Design
(http//www.electronicdesign.com/Articles/Index.cf
m?AD1ArticleID9018)
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H-Bridge Power Circuitry
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H-Bridge Power Circuitry
Reference Lon Glazner, Parallax
(http//www.parallax.com/dl/docs/cols/nv/vol2/col/
nv52.pdf)
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H-Bridge Power Circuitry
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CCS3000_Rev1 - Schematic
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CCS3000_Rev1 - Layout
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CCS3000_Rev1

• Problems
• Hole sizes for various parts (i.e. diodes, screw
  terminal block)
• LM317 (voltage regulator) pin assignments
• Incorrect schematic for the VCCS
• Accidental connections in schematic

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CCS3000_Rev2 - Schematic
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CCS3000_Rev2 - Layout
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CCS3000_Rev2

• Changes
• Corrected known errors from Rev 1
• Added capacitors on the outputs of the voltage
  regulators to filter out ac voltages (noise)
• Problems
• Minor incorrect connections
• Code to deal with limit switches was incorrect

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CCS3000_Rev2

• Trip to Bechtel
• We went to Pittsburgh to test Rev 2 on their
  actual simulator.
• We achieved partial success turning the motor in
  the forward direction.
• As we were trying to figure out why the limit
  switches were not working correctly (using a
  digital multimeter), we shorted out two pins on
  the board.
• Because of this

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Catastrophic System Failure
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Catastrophic System Failure
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Catastrophic System Failure
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CCS3000_Rev3

• Changes from Rev. 2
• Added microcontroller reset switch
• Added fuses on voltage regulator outputs
• Fuse holders added for easy replacement
• Added Zener diode for overvoltage protection on
  A/D converter
• Switched to dedicated 5, 12, -12 V regulators
  and reduced number of resistors used
• Added LEDs (5) for indications diagnostics

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CCS3000_Rev3
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CCS3000_Rev3
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CCS3000_Rev3

• PCB Rev. 3 difficulties
• LEDs on limit switch inputs caused voltage drop
• 1 V voltage divider was connected to ground
  through SPEED input, so we did not get a constant
  1 V
• Fixed by adding a buffer to voltage divider
  output

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Second Trip to Bechtel

• April 14, 2008
• Testing was successful!
• CranCon demonstrated prototype for Ryan Muller to
  his satisfaction. All subsystems were fully
  functional.

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Second Trip to Bechtel
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Second Trip to Bechtel
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Second Trip to Bechtel
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Second Trip to Bechtel
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Final Revision

• Made necessary schematic changes
• Buffer and capacitor on output of 1 V voltage
  divider
• Limit switch LEDs on separate HCS12 output pins
• Additional GND screw-terminal connections

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Final Revision
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Final Revision
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Final Revision

• Ordered PCBs, microcontrollers, and other parts
• Enough parts to construct 10 units
• Expected arrival sometime next week
• Build
• Test
• Deliver

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S.E.E.D.

• Senior Experience in Electrical Design
• Comprehensive project design through production.
• Manageable scope.
• Reproducible product.
• Demonstrated individual group EE/CE knowledge.
• Satisfied customer met requirements, timeframe,
  price.

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Thanks

• GCC Electrical Engineering Department
• Dr. Timothy Mohr
• Dr. Thomas Cavicchi
• Dr. Mike Bright
• Dr. Alan Christman
• Dr. Frank Duda
• Mr. Scott Jaillet
• Bechtel Corporation
• Bechtel has funded the project production
  units.
• Ryan Muller
• Dan Roseum

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Questions?