Remote Fire Alarm

1
Remote Fire Alarm

• Nick Rymer
• Brian Robinson
• Adam Lehotay
• Josh Bertovich

2
Introduction

• Problem
• Location with Multiple Buildings
• Unmanned Buildings
• Buildings hundreds of feet apart

3
Introduction

• Existing Systems
• Stand Alone Alarms
• Someone Must Hear Alarm
• Hardwired
• Complex and Expensive
• Inflexible

4
Solution

• Wireless System
• Easy Installation
• Can Monitor Many Buildings
• 1 unit can Monitor Entire System

5
Principle of Operation

• 1 Central Unit
• Displays Information About Entire System
• Up to 8 Remote Fire Alarms
• Transmit Status to Central Unit

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Central Unit
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Remote Unit
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Remote System

• Remote Alarm Status
• Normal Operation
• Fire
• Low Battery
• Communication Loss
• Adding Devices
• Removing Devices

9
Performance Specification

• User-friendly installation, setup, and operation

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Performance Specification

• Central and Remote Units will be powered by 120
  VAC
• Battery backup in the Remote Units
• Maximum of eight remote units controlled by one
  central unit
• The status of all remote units will be known by
  the central unit in less than one second
• Remote Units will detect smoke with ionization
  chambers

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Performance Specification

• Maximum communication distance between central
  unit and remote unit will be 500 feet with
  obstructions

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System Design

• Block Diagram of Remote Unit

5V
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Remote Unit PIC Operation

• Infinite loop which checks the status of I/O pins
  on the PIC
• Devices being checked on I/O pins
• Transceiver
• IC Smoke Detector Chip (Ionization chamber and
  battery level monitoring)
• Learn Button
• Abnormal events on a device cause a sub-function
  to be called

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Fire Alert Function

• Invoked when a local fire is detected
• The local alarm is sounded and the Central Unit
  is notified of event

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Remote Fire Function

• Executed when there is a fire at another location
• Transceiver receives signal from Central Unit to
  sound alarm

16
Low Battery Alert Function

• Executed when battery power drops near minimum
  operational levels
• Receives alert from IC Smoke Detector Chip and
  transceiver sends alert to central unit

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Learn Function

• Executed when the user presses the learn button
  on the local unit
• Transceiver sends signal to Central Unit
• Central Unit sends signal containing the network
  address that the unit will respond to when polled

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Central Unit Block Diagram

• Shows connectivity of central units components

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AC-DC Adaptor

• Converts AC output from a standard 60 Hz 120 VAC
  electrical outlet into 6 Volts DC
• The output of this block is the input to the 5
  volt regulator block

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Power Regulator

• Regulates the voltage so chips will function
  normally as well as be protected from over
  voltage
• Regulator holds the voltage at 5 volts 5
• Remote units regulator will do the same as the
  central units regulator except that it will
  regulate power for fewer devices

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Internal Switch

• Internal switch has inputs from the battery and
  AC-DC adapter
• Switch connects either the battery or the AC-DC
  adapter to the regulator
• Battery will only be connected to the regulator
  when the AC-DC adapter is no longer providing a 6
  VDC input to the switch

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Transceiver

• FM modulation at 900 MHz
• 8-bit data packets represent either a remote unit
  address, central unit address, or a certain
  function to be executed
• RS-232 protocol used to transferred data between
  transceiver and microcontroller

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Transceiver

• RF data received by transceiver
• Data-out buffer
• Request-to-send
• Data from microcontroller
• Data-in buffer
• Clear-to-send

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Modes of Operation

• Sleep mode
• Low power consumption
• Transmit mode
• Transceiver takes the data from the data-in
  buffer and broadcasts it to the other transceiver
  
• Receive mode
• Transceiver receives data from the other
  transceivers and stores it in the data-out buffer
• Transition mode
• Transition time between modes

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Modes of Operation
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Utilizing Modes of Operation

• Modes of operation should be used efficiently to
  save power
• Transceivers in sleep mode 99 of the time
• Central unit transceiver polls the next remote
  transceiver every second

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Central Unit PIC Operation
Purpose

• Manages communication with remote devices
• Maintains identification for each remote device
• Processes and responds to user input
• Controls the display

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Central Unit PIC I/O

• Infinite loop which checks the status of I/O pins
  on the PIC
• Devices sending information to input pins
• Transceiver
• Learn/Remove Buttons
• Alarm Specific Buttons
• Devices receiving information from output pins
• Transceiver
• LCD display
• Alarm LEDs and speaker

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Fire Alert Process

• Performed when fire detection is received from
  transceiver
• Sends signal to trigger all remote devices
• Displays fire detection message and alarm of
  concern on the display

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Low Battery Process

• Performed when low battery is received from
  transceiver
• Displays low battery message and alarm of concern
  on the display

31
New Device Process

• Performed when user presses the learn button
• Halts normal operation
• Selects and transmits identification for new
  device
• Waits for new device to confirm its identity
• Normal operation is restored

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Remove Device Process

• Performed when user pushes the remove button and
  selects an alarm
• Requires user confirmation and then the selected
  alarm identification is cleared

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Comm. Loss Process

• Performed when a remote device does not respond
  to a status prompt
• Displays communication loss message and alarm of
  concern on the display

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Performance Analysis
Central Unit Power Consumption

• Typical Power used by Central Unit
• Power ITyp 5V, 165mA 5V .825 Watts
• Maximum Power used by Central Unit
• Power ITyp 5V, 720mA 5V 3.6 Watts
• Maximum Power Supplied AC-DC adapter
• Power IMAX 6V, 1A 6V 6 Watts
• Maximum Power Supplied by Regulator
• Power IMAX 5V, 1A 5V 5 Watts
• Excess Capacity
• AC-DC adapter Supplies 2.4 Watts of Extra Power
• Regulator loses 1 Watt of Power in Heat
• Regulator Provides 1.4 Watts of extra Power to
  Central Unit

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Performance Analysis
Remote Unit Power Consumption

• Typical Power used by Remote Unit
• Power ITyp 5V, 15mA 5V .075 Watts
• Maximum Power used by Remote Unit
• Power ITyp 5V, 590mA 5V 2.95 Watts
• Maximum Power Supplied by rectifier
• Power IMAX 6V, 1A 6V 6 Watts
• Maximum Power Supplied by Regulator
• Power IMAX 5V, 1A 5V 5 Watts
• Excess Capacity
• Ac-Dc adapter Supplies 3.05 Watts of Extra Power
• Regulator loses 1 Watt of Power in Heat
• Regulator Provides 2.05 Watts of extra Power to
  Remote Unit
• Battery Life Calculations
• Standard 4 AA Battery Life 6V _at_ 1300 Milliamp
  Hours
• Central Unit Battery Life _at_ Typical Current
• I 1300 / 15 86.67 Hours

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Performance Analysis

• Transceiver Performance
• Transmit power output of 140 mW
• Receiver sensitivity of -114 dBm
• Transmission range can reach up to 1500 feet
• The serial data throughput is approximately 1100
  bps
• Excess capacity
• 1000 feet extended range beyond required range
• only a fraction of the data throughput will be
  needed

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Performance Analysis

• PIC Performance (Central and Remote Units)
• 256k of program memory
• PIC will be set to run at 2MHz
• Excess capacity
• Small amounts of memory will be required relative
  to the available 256k
• At 2MHz will be processing data at a much faster
  rate than would be required to meet time
  constraints of the system