wireless intelligent sensor modules for home monitoring and control presented by: bui, phuong nhung,...

Wireless Intelligent Sensor Modules for Home Monitoring and Control

Wireless Intelligent Sensor Modules for Home Monitoring and Control

Presented by:BUI, Phuong Nhung, 裴芳绒

António M. Silva1, Alexandre Correia1, António J. Gano1, António M. de Campos1, Isabel Teixeira,

ContentsContents

Abstract1

Introduction2

System Description3

Data Communication and System Interfacing 4

5

6

Preliminary Results

Conclusions

AbstractAbstract

In this paper: wireless intelligent sensor system Bluetooth communications protocol Low cost analog to digital sensor for low-

frequency 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.)Abstract (cont.)

Purpose Home monitoring and control of several physical

variables

IntroductionIntroduction

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 DescriptionSystem 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


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 interfacingSensor 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


Ms: The output of the system to a signal Si. k & Moff : The unknown gain and offset of the global linear measuring system


Measure 3 signals:

Compute the ratio

Sref : a known reference sensor or component value


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 orcapacitive sensor elements

low-cost sensor interface that can be successfully used in measuring

low-frequency signals based on resistive orcapacitive sensor elements

Data ProcessingData Processing

Functionalities: Internal data acquisition & processing

Procedures Local control Digital data management and transmission


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


Two channels: Measure four voltage signals 0 to +3V 10-bit resolution AD converter

internal data processing calculations Floating-point math


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 CommunicationData 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

configurationRS232 connection for data communications

System InterfaceSystem Interface

Use digital ASCII strings =>ASCII commands System configuration Management Data acquisition

Implement Custom ASCII frame Custom handshake protocol


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 resultsPreliminary 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%.


The transfer functions


The correcting function is given

ConclusionsConclusions

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

wireless intelligent sensor modules for home monitoring and control presented by: bui, phuong nhung,...

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