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Senior Project – Electrical Engineering – 2005
Wireless Baby Monitor
Nelson Rosario, Farida Siddiqi
Advisors: Professor Ekram Hassib
Professor Emad A. Andarawis
Abstract: The principle behind our wireless infant monitoring system involves the activation of a video camera by the detection of a child’s cry in the environment.
Once the video camera has been activated, video and sound are transmitted to the parent, through wireless communications, in which the parent will receive this data
on a handheld device. In this project the theory behind infant cries is researched and implemented in the design of a triggering methodology for activating the
monitoring system and alerting the parents.
Why design a new wireless baby monitor?
- A design which will combine the features offered by individual wireless
baby monitors into one system and incorporates video and audio
transmission with the detection of sound.
Design of FAN05
Microphone/Camera- captures analog audio/video signal and
sends to transmitter
Transmitter- receives audio/video signal converts to modulated
radio frequency signal and transmits to receiver
Receiver- picks up modulated radio frequency, converts it to
original audio/video signal
Trigger Circuit – Triggers the monitor to turn on and emits an
audio signal to get the response of the parent.
Monitor- device which allows parent to see child
The Trigger Circuit:
The
trigger circuit is the portion of the apparatus that consists of the microphone,
amplifier, bandpass filter, diode rectifier, low pass filter, comparator, and timing circuit.
The trigger circuit starts with a child's cry that will be picked up by the microphone. Then
the signal will be amplified and sent through a band pass filter. If the frequency of the
voice is between 900 Hz and 1200 Hz then the signal will be rectified by the diode then
the signal will pass through a low pass filter to eliminate the high frequency components.
The resulting DC signal will trigger one of the comparator inputs. Then a reference
voltage of 0.5V will be connected to the second input of the comparator. When the
rectified signal is lower than 0.5V then we have a low output. When the rectified signal is
higher than 0.5V then we have a high output. When the output of the comparator is high
this will trigger the reset pin at the TLC555 timing circuit generating a square wave
output. The square wave is added to the video and audio signals to be transmitted. This
square wave is used to generate an alarm signal at the receiver.
Infant Cry Modes:
Infants have three modes of
vocal mechanisms:
-Phonation: the vocal cords
are fully vibrating periodically
at a frequency between 250
Hz and 650 Hz.
-Dysphonation: turbulence
noise is generated at the
vocal cords and is modulated
by vocal fold vibrations.
Frequency between 650 Hz850 Hz
-Hyperphonation: when the
frequency of the vocal cords
shifts to 900 Hz- 1200 Hz.
For our purposes we are
interested in this frequency
range.
Analog Audio Signal Results:
Microphone signal : music is playing
on the computer volume 61,
approximately 15 inches from
computer speaker
Microphone signal: music is playing
on the computer volume 100,15
inches from computer speaker
Video Results for FAN05:
video signal when a hand is approximately 7.5
inches from the lens
video signal when a hand is standing
approximately 21 inches from the camera lens
Pspice-Filter Circuit Design
Results of Pspice for filter design
Results of Constructed Circuit
Not triggering at 800Hz
Triggering at 1100Hz
Triggering at 1200Hz
Output of TLC555 Timing Circuit