Wireless Intelligent Sensor
Modules for Home Monitoring
and Control
António M. Silva1, Alexandre Correia1, António J. Gano1, António M. de
Campos1, Isabel Teixeira,
Presented by:
BUI, Phuong Nhung, 裴芳绒
Contents
1
Abstract
2
Introduction
3
System Description
4
Data Communication and System Interfacing
5
Preliminary Results
6
Conclusions
Abstract
In this paper: wireless intelligent sensor
system
 Bluetooth communications protocol
 Low cost analog to digital sensor for lowfrequency signals
 Resistive and capacitive sensor elements
 Built-in floating-point data processing
functions
 Digital ASCII string as an output
 Low-power RISC microcontroller
Abstract (cont.)
Purpose
 Home monitoring and control of several physical
variables
Introduction
Management of physical variables: Important ?
 Improve
• Domestic comfort
• Security
• Rational use of energy
How the system reach the requirement?
 Monitor & control some environmental variables
(temperature, humidity, light incidence)
 Use a network of intelligent sensor modules +
actuators with a set of low frequency variables
 Wireless Bluetooth protocol
System Description
System Description
Main built-in functions:
 2 sensor channels for resistive and/or capacitive
sensors
measure a wide range of low-frequency
physical and chemical variables
 4 channels for sensors with voltage signals within
the range of 0-3V
 I2C serial real time clock with calendar
set the acquisition times & other functional time
schedules
System Description
Main built-in functions:
 Internal 256KByte of non-volatile I2C memory
data-logging
 Sensor circuit interfaces
 power-saving modes
Set the microcontroller into deep sleep mode
 Serial RS232 port
 Wireless communications module using the serial
profile of the Bluetooth protocol
Sensor interfacing
The intelligent sensor module uses a Universal
Transducer Interface (UTI) circuit:
 low-cost and flexible analog to digital
• Directly convert the signal from a sensor element into a
digital signal
• With a time domain variation =>Easily code into a
digital word
 Low-frequency signals
• Easily convert signals based on resistor / capacitance
sensor elements
Sensor interfacing
Ms :
The output of the system to a signal Si.
k & Moff : The unknown gain and offset of the global linear
measuring system
Sensor interfacing
Measure 3 signals:
Compute the ratio
Sref : a known reference sensor or component value
Sensor interfacing
Evaluate the procedures:
 Compensate for any drift of the gain and offset of
the system
 Make the accuracy of the measurement
dependent on:
• the characteristics of the reference component used
• processing errors in the digital domain
low-cost sensor interface that can be
successfully used in measuring
low-frequency signals based on resistive or
capacitive sensor elements
Data Processing
Functionalities:
 Internal data acquisition & processing
Procedures
 Local control
 Digital data management and transmission
Data Processing
Parameters for programming the overall data
acquisition process & transfer functions
coefficients
 Store in local non-volatile memory
 E2PROM memory
Measure the output periods of the UTI
 Use the internal 16 bit timers of the
microcontroller
 Counting sampling period of 1μs
Data Processing
Two channels: Measure four voltage signals
 0 to +3V
 10-bit resolution AD converter
internal data processing calculations
 Floating-point math
Data Processing
Data Processing
Thus with clock frequency of 4MHz




Acquisition time: 360 ms
Polynomial computation time: 3.75 ms
Maximum sampling frequency: 1 sample/s
Output data: a digital value of the measured
sample with an ASCII representation
Data Communication
Internal wireless communications module
 Bluetooth protocol
 Spread Spectrum by frequency hopping in the
ISM 2.4GHz Band
 Transmission range: 100 m
 Data transfer rate: 200Kbps
 Use AT Command Set for setup and
configuration
RS232 connection for data communications
System Interface
Use digital ASCII strings =>ASCII commands
 System configuration
 Management
 Data acquisition
Implement
 Custom ASCII frame
 Custom handshake protocol
System Interface
System Interface
System Interface
Graphical user interface
 Use the Microsoft VisualBasic.NET
 2 main option tabs:
• Interface Configuration
• Module Information
 Program, control and get sensor data from
several associated intelligent sensor modules
 Communicate with it
• Wireless Bluetooth protocol
• Serial RS232 connection
Preliminary results
 Implement a preliminary prototype with two UTI
measuring channels
Variable Name
Value
Temperature
-15ºC to +55ºC
Relative humidity
0-100% RH
Low TCR precision resistance
Rref=100 Ω ±0.1%
Ceramic capacitor
Cref=100pF ±10%.
Preliminary results
The transfer functions
Preliminary results
The correcting function is given
Preliminary results
Conclusions
Design and implement:
 A wireless intelligent sensor module
• Wide range of low frequency signals
• Low cost front-end interface for resistive and capacitive
sensor elements
• Modular architecture
• Completely programmable using a set of ASCII
commands for device configuration and data
acquisition
 Preliminary result
• Measure ambient temperature and relative humidity
• Show promising results