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,

Contents Abstract1 Introduction 2 System Description 3 Data Communication and System Interfacing Preliminary Results Conclusions

Abstract  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.)  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

 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  I 2 C 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 M s : The output of the system to a signal S i. k & M off : The unknown gain and offset of the global linear measuring system

Sensor interfacing  Measure 3 signals:  Compute the ratio S ref : 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 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  E 2 PROM 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

 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

 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 NameValue Temperature-15ºC to +55ºC Relative humidity0-100% RH Low TCR precision resistanceRref=100 Ω ±0.1% Ceramic capacitorCref=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