EE Senior Design Team b
Final Report for Push-Button Power

Abstract

In contrast to conventional college laboratory power supplies, Push-Button Power is stable and user-friendly. The device features fixed 5V and ±15V supplies and a variable ±35V supply. A 32-bit Motorola 68F333 microcontroller manages a combination of switching and digitally controlled shunt supplies. The user interface consists of a custom keypad for input and a multi-line LCD panel for output. In addition to technical specifications and a user manual, a final budget for the project is presented.

To: Dr. Henry Welch

Date: Monday 19 May 1997

By:

• William Bernard
• Eric Durant
• Jason Hutchinson
• Charles Ulmschneider

Contents

• Executive Summary (on this page)
• Introduction (on this page)
• Problem Statement and Objectives (on this page)
• Functional Specifications
  • Electrical Capabilities
  • User Interface
    • Use Cases
      • Set Voltage
      • Stop System
      • Open Circuit While Controlling Current
• Design Documentation
  • System Block Diagram
  • Supply Blocks
    • Variable Supplies
    • Fixed Supplies
    • Design Parameters
  • Control Blocks
    • Supporting Subsystems
      • Keypad and Controller
      • LCD Display
      • Alarm
      • Master Control Relay
      • Summary of Support Subsystems I/O Utilization
    • Firmware
      • Main Loop
      • High Level Supply Control
      • Low Level Supply Communication
      • Display
      • Keypad
      • Error Checking / Safety
      • Utility
• Laboratory Testing
• Budget
  • Time
  • Cost of Parts
• Conclusion
• Appendix A: References
• Appendix B: Acknowledgments
• Appendix C: Tracking Progress on the Web
• Appendix D: Firmware Flowcharts
  • Main Loop
  • High Level Supply Control
    • Initialize Supplies (initSupplies)
    • Regulate Supplies (regulateSupplies)
    • Update Supply Set Point (updateSetPoint)
    • Calculate Moving Average (historicAverage)
    • Initialize Reading History (initHistory)
    • Update Reading History (updateHistory)
  • Low Level Supply Communication
    • Get Reading (getReading)
    • Put Supply Data on Data Lines (putSupplyData)
    • Put Supply Address on Address Lines (putSupplyAdr)
  • Display
    • Initialize Display (initDisplay)
    • Update Display (updateDisplay)
    • Put String on Display (putString)
    • Put Center-justified String on Display (putStringCenter)
    • Clear Display (clearDisplay)
    • Strobe Display Enable Pin(s) (strobeDispEna)
  • Keypad
    • Keypad Interrupt Service Routine (keypadISR)
    • Validate Keypad Entry (valEntry)
  • Error Checking / Safety
    • Toggle COP (toggleCOP)
    • Error Check (errorCheck)
    • Handle Error (handleError)
    • Put Error Message on Display (putError)
  • Utility
    • Encode Voltages and Currents (encode)
• Appendix E: Firmware Code
• Appendix F: Compiler Configuration
  • mc68332.s
  • start.s
  • c68.ld
• Appendix G: Subsystem Hardware Specifications
• Appendix H: Supply Schematics
• Appendix I: Calibration
  • Positive 5V Section
  • 15V Section
    • Positive
    • Negative
  • Variable Section
    • Positive
    • Negative
• Appendix J: Microcontroller Specifications
• Appendix K: Cost Analysis
• Appendix L: User's Manual
  • Description
  • Instructions
    • Turning the unit on and off
    • Enabling and disabling the output
    • Setting a voltage or current
    • Handling Errors
    • Troubleshooting
  • Electrical Specifications
  • Warranty
  • Registration Card

Figures

• Figure 1: Keypad Layout
• Figure 2: Display Format
• Figure 3: System Block Diagram
• Figure 4: Block Diagram For Supply Section
• Figure 5: Variable Supplies Block Diagram
• Figure 6: Fixed Supplies Block Diagram
• Figure 7: Keypad Subsystem Schematic
• Figure 8: LCD Display Schematic
• Figure 9: Alarm Subsystem Schematic
• Figure 10: Master Control Relay Schematic
• Figure 11: Firmware Function Hierarchy
• Figure 12: Fixed Sections: +5V and ±15V (I)
• Figure 13: Positive Variable Supply (I)
• Figure 14: Negative Variable Supply (I)
• Figure 15: Example Error Message (L)

Tables

• Table 1: Electrical Specifications
• Table 2: Keypad I/O Configuration
• Table 3: LCD I/O Configuration
• Table 4: Alarm I/O Configuration
• Table 5: Master Control Relay I/O Configuration
• Table 6: I/O Pin Requirements
• Table 7: Accumulated Project Time
• Table 8: Cost of Positive Variable Supply (K)
• Table 9: Cost of Negative Variable Supply (K)
• Table 10: Cost of Fixed +5V and ±15V Supplies (K)
• Table 11: Cost of AC to DC Converter (K)
• Table 12: Cost of Control Subsystems (K)
• Table 13: Troubleshooting (L)
• Table 14: Electrical Specifications (L)

Executive Summary

Push-Button Power has been implemented as specified in the Design Report of 24 February 1997. The project's final cost was $48 948, which is 22.4% over the budget of $40 000. The prototype consists of a ±0-35V variable supply, ±15V fixed supply and a +5V fixed supply, controlled and monitored by a Motorola 68F333 microcontroller. A 20-key keypad is used for input and a 4-line by 40-character LCD panel is used to display the voltage and current for each supply.

Introduction

This report builds on the Feasibility Report submitted on 18 November 1996 and the Design Report submitted on 24 February 1997. Since that time, the team has completed the design of both firmware and hardware for Push-Button Power. Objectives of the project, its functional specifications, design of all hardware and firmware components, laboratory testing and budget are covered. A user's manual is included in Appendix L: User's Manual.

Problem Statement and Objectives

A common problem in undergraduate engineering laboratories is measuring power supply effects and accurately setting voltage and current. This is due to analog controls which are subject to drift and aging, making them difficult to fine tune. Team ß's power supply lets the user enter parameters on a keypad, much as modern oscilloscopes provide discrete control via keyed input.