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This system installed in a car monitors the voltage and current from the lead ... Audio alert in car and to wireless receiver to warn of significant battery drain ...

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Smart Battery System Monitor

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smart battery system monitor

Smart Battery System Monitor

ECE 445 Group 3

Jason Hoban

David Atwood

  • This system installed in a car monitors the voltage and current from the lead-acid battery.
  • Prevents accidental battery depletion
    • Ensures car ignition capacity is maintained
    • Preserves the life of the battery
  • Real-time voltage and current monitoring to display battery voltage level and battery life remaining
  • Audio alert in car and to wireless receiver to warn of significant battery drain
  • Automatic cut-off of system loads to ensure ignition level charge remains
  • Simple one push reset to transfer control back to user
msp 430f156
MSP 430F156
  • Reason for Selection
    • Low Power Consumption
    • High Functionality
      • 2x ADC, DAC, UART, Multiple Digital I/O
    • Size
dc dc conversion
DC-DC Conversion
  • LM317 – 3 Terminal Adjustable Regulator
  • TX Side
    • 12 Volts to 3.3V and 5V
  • RX Side
    • 9 Volts to 5V

DC-DC Schematic

dc dc tests
DC-DC Tests

Transmitter Side

Receiver Side

current sense module
Current Sense Module
  • LTC6101:High Voltage, High-Side Current Sense Amplifier
  • Precision .005Ω Sense Resistor

Current Sense Schematic

voltage monitoring
Voltage Monitoring
  • Original Design
    • MAX6652 – Temperature Sensor and System Monitor
  • Revisions
    • Resistive Divider
    • Differential Amplifier Op-Amp Design

Op-Amp Schematic

buzzer and pushbutton
Buzzer and Pushbutton
  • Piezoelectric Buzzer
  • Pushbutton De-bouncing Circuit

Circuit and RC Equation

high power load switch
High Power Load Switch
  • High Ic rated NPN BJT
  • Smaller NPN BJT to drive the base
    • Controlled by MCU
  • Loads cut when Battery <= 11V

Original BJT Switch Set-up

bjt design constraints
BJT Design Constraints
  • HP BJT must be operated in saturatation
    • Initial tests show base current of at least 50mA required to drive base (VB=3.3V and IB = 50mA yields VCE = 210mV)
  • MSP430 I/O should not exceed 6mA
  • MPS2222 BJT rated at Ic,MAX = 600mA
  • Voltage from MSP430 must have enough headroom to operate all transistors at VBEON but not exceed current limit of the MPS2222
final switch set up
Final Switch Set-Up
  • VOUT from MSP430 = 2.25V achieves IB,Q1 = 6mA
    • On-chip DAC required
  • Q1, Q2 drive 300mA into base of Q3
  • Saturation achieved as evidenced by VCE,Q3 = 124mV and VLOAD = 11.79 V for a 11.95 V Battery Source

Final Schematic

tx rx circuit
TX/RX Circuit
  • LINX 416-ES Transmitter and Receiver
  • Design Changes
    • Frequency to Voltage Converter
    • Uses Transistor to Draw Required Current
rx pcb
  • Created PCB
    • Issues with Incorrectly drawn trace and grounding
    • Scrapped to Proto Board
  • PC-1602-Q 2x16 LCD with BPI-216 Serial Backpack
  • Serial RS-232
    • Inversion Transistor required for UART output
  • Interrupt Routine
    • Cutting off of loads
    • Pushbutton Reset
  • MSP Coding
    • Less readily available information than more common PIC Microcontroller option
  • LCD Display
    • Struggled with RS-232 and timing issues at first
    • Lack of Crystal at Deadline
  • I2C Code
    • Abandoned due to software issues and time constraints
    • ADC functionality allowed for Op-amp solution
  • TX/RX
    • Transmission Worked with Power Supply on Proto Board but full scale implementation created problems
    • PCB Issues
  • With more time system could have been further optimized and expanded
    • MSP operation in Low Power Mode is made possible by sourcing clock from external 32kHz crystal
    • Further Research into using components with lowest power drain (i.e. instead of available LCD)
    • PCB Board Design could be greatly reduced in size
    • I2C Chip offered temperature monitoring
    • Time left Equation could be improved
      • Battery drain is not strictly linear
      • Averaging could produce more stable time left display
  • Teaching Assistant Paul Rancuret
  • Professor Gary Swenson
  • Mark Smart and everyone else in Parts Shop
  • Professor Philip Krein
  • Texas Instruments for MSP Debugger Donation