Small, Lightweight Speed and Distance Sensor for Skiers and Snowboarders

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Team 10

• Small, Lightweight Speed and Distance Sensor for
  Skiers and Snowboarders

Power Management
Mark Blair Gabe Cropsey Matt Lambert Rob
Vermurlen Aaron McCloy Shanker Balasubramaniam
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Introduction

• History
• Lack of management
• Auto-off
• Low power states
• Energy Star
• Importance
• Battery life
• Heat

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Topics

• Power Source
• Conversion
• Software Integration
• Sleep Modes in Hardware

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Batteries

• What is a battery?
• Energy storage device
• Multiple Electrochemical cells
• Series connection produces desired voltage
• Portable battery technologies
• NiMH
• NiCd
• Li-Ion

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Battery Terminology

• Capacity
• Energy stored in the cell (Ah)?
• Gravimetric Energy Density
• Energy stored per unit weight (Wh/kg)?
• Power Density
• Power supplied by cell in a 30 sec pulse (W/kg)?
• Voltage Depression
• Memory Effect
• Life Cycle
• Measurable life of the cell

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Battery Technologies
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Li-Ion Protection

• Lockout voltage set by R1 and R2
• VB 1.25 V I R4 1.37V
• VBATT drops below lockout
• SW1 pMOS off at high input, load is
  disconnected
• R5 added to provide hysteresis for
  oscillating when load disconnected

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Power Regulation

• AC to AC
• AC to DC
• DC to DC

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AC to AC

• Step up/Step down Transformer (Turns Ratio)?
• Power in Power out
• VpNpdF/dt
• VsNsdF/dt
• Vs/VpNs/Np
• Is/Ip Np/Ns

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AC to DC

• Full wave rectifier
• Converts a sine wave to a constant voltage
• Minimize ripple
• Battery Chargers

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DC to DC

• Boost Converter (Power Amplifier)?
• Increase voltage
• Vout Vin/(1-Duty Cycle)?
• Buck Converter (Power Divisor)?
• Decrease voltage
• Vout VinDuty Cycle
• Voltage Divider
• Parallel resistor combination
• Low voltage and current

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Voltage Regulator Block

• Power controlled by processor
• Integrated by using VRB components
• VRB Chip
• Inductor
• Capacitor
• Needs small size, large capacitance and
  inductance

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Dynamic Power Management

• Software approach
• Two types of algorithm
• Predictive
• Stochastic
• Interact with hardware
• Advanced Configuration and Power Interface
  (ACPI)?
• Developed by Microsoft, Intel and Toshiba
• Hardware and Software standard
• General or specific application

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Dynamic Power Management

• Filter Drivers
• Attach to hardware
• Generic Interface
• Used by Power Manager
• Power Manager
• Implements policies governing power
• Sends to FDs to change power states

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Sleep Modes on PIC

• What is sleep mode?
• Power-down Mode
• Very low current consumption
• I/O ports not updated
• Oscillator turned off
• Reduce current draw
• Stop any I/O current draw
• Disable any external clock
• Power down comparator unit

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Sleep Mode Functionality
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Sleep Modes on PIC

• How to recover from sleep mode
• Reset input on MCLR pin
• Interrupt from INT pin or peripheral device
• Use of a Watch Dog Timer (WDT)?
• Separate clock timer

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Summary

• Power Source
• Conversion
• Software Integration
• Sleep Modes in Hardware