EE 43334: Doorbell Repeater

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EE 4333/4 Doorbell Repeater

• Jacob Borgeson and Chris Del Rio
• Advisor Dr. Trost
• Instructor Dr. Zieher
• Date Fall 2004

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Project Definition

• Design Test and Build a working device which will
  repeat a Doorbell signal in other rooms of
  building
• Must be Wireless Battery Powered
• Use a sound or light signal (for hearing
  impaired)
• Low power consumption
• High efficiency
• At least 250 ft range

3
Initial Ideas

• Attach onto existing doorbell system
• Not feasible due to power problems
• Portable Receiver
• Vibrating device inside?
• Sound and light output
• Alternate power sources

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Project Block Diagram
Vcc
DC Supply
RF Transmitter
Voltage Regulator
Light/Sound
RF Receiver
Del Rio
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RH Antennas
Omni directional Helical antenna
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Transmitter Schematic
Del Rio
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Transmitter Layout
Del Rio
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Transmitter
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Transmitter Test

• Vcc on Pin 2 and Pin 3 3.2V
• Vpp 2V on Pin 24

Del Rio
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Voltage Regulation

• LM2671 3.3V switching regulator
• 8 pin DIP
• 5 external components

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Receiver Schematic
Del Rio
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Receiver Layout
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Receiver
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Results

• Diode lights up and buzzer makes a faint sound
• Need more current
• Range of 120 ft inside (basement)
• Range of 160 ft w/ transmitter in Lankford lab
  while we are in parking lot

Borgeson
15
Practical Results

• Taken to my House
• Left transmitter at Front Door
• Worked across alley in my Neighbors house
  consistently
• Only did not work a few times (bad perf board
  connections)

Borgeson
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Data
Borgeson
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Implementing the Speaker

• Decided to use a speaker with actual doorbell
  sound instead of buzzer
• Problem solved by sound module made by Radio Shack

Borgeson
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Sound Module
Borgeson
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Doorbell.wav

• Left plot vs time (1.04s)

• Right Normalized frequency plot
• Fmax 4kHz

Borgeson
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Speaker Problems

• Output not loud enough
• Larger impedance speaker
• Move to Piezo speaker with 1 kO

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Piezo Speaker

• 102-1141 by CUI Inc.
• 20 Vpp
• 90 dB at maximum
• 78 dB _at_ 9 Vpp
• Not outputting correct intensity of sound
• Does output correct sound

Borgeson
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Amplification

• Simple Audio band amplifier
• Tried Several
• Some too simple
• Some too complicated
• Have not perfected it as of yet
• Based on a model from circuitos.tripod.cl

Borgeson
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9V 1.5W Amplification
Borgeson
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Amplification Simulation
Borgeson
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Accomplishments

• Successfully transmitted and received signal on
  test boards
• Reliable signal at 160 ft.
• Maximum transmission with test boards 195 ft.
• Capable of sound and light output
• Designed prototype circuit boards
• Successful tests of transmitter boards

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Parts Problems
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Future Objectives

• Receive, assemble and test receiver boards.
• Re-engineer sound module
• Use our own micro-controller
• Get Amplification to perfect level and quality

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Gannt Chart
Borgeson
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Budget
Borgeson
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Acknowledgements

• Dr. Trost
• www.linxtechnologies.com
• www.rentron.com
• www.lynxmotion.com
• Dr. Nutter
• http//circuitos.tripod.cl/schem/r73.gif

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Questions?