1. Sensors and Robotic Environment for Care of the Elderly S. C
Sensors and Robotic Environment for Care of the Elderly S. C. Mukhopadhyay and G. Sen Gupta Massy University, Palmerston North, New Zealand Singapore Polytechnic, Singapore
Presenter: Yang Fei
The 10th of December, 2011

2. System developed for the elder care
Sub-systems:
1 Selective Activity Monitoring(SAM) system(detect the electric appliances)
2 Low-cost Physiological Parameters Monitoring(PPM) system
3 Web-enabled, robot-based vision system (get pictures)

3. Selective Activity Monitoring(SAM) system
Objective: monitor electrical appliances
Cellular modem
Appliance
Sensor Unit
RS232
RS232 PC
Appliance
Sensor Unit
Central Controller Unit
Appliance
Sensor Unit
1 The Sensor Units
2 The Central Controller Unit
3 A PC and a cellular modem
Function block diagram

4. System architecture
Electrical appliance: such as a reading lamp, room heater. (detect the current)
Communication between PC and the central controller: RS232.
Communication between sensor units and the central controller: Radio.
Radio communication:
frequency: 418MHz
maximum data transfer rate: 40kbps
A cellular modem: send short messages
Wavecom Wismo cellular modem-WISMO218
(GSM/GPRS wireless communication module)

5. Core components of the Sensor Unit(SU)
microcontroller

6. Design of the Sensor Unit
Power: 230V/50Hz AC mains
5V&3.3V DC mains
Radio Frequency module:
Radiometrix(company) BiM418 transceiver
half-duplex operation at 418MHz
Left:TXM transmitter right: SILRX receiver

7. Parameters of the system
TxSelect/ RxSelect: configure the transmit or receive mode of the RF transceiver
Tx/Rx: transmit and receive data (data rate: bauds)
series communication ports
Microcontroller: SiLab C8051F020
radio frequency module
TxSelect
RxSelect Rx Tx
microcontroller

8. Microcontroller
ATmega128

9. Baud
One concept in analog modulation: symbols per second or pulses per second.
M: different voltage levels
R: bps
fs: baud 1
0 1 1
0 1
1 1
1 0
0 0

10. Current transformer connections and circuitry
CT(Current Transformer): coil based on electromagnetic induction
AC current
DAC: programmable voltage of the Digital-to-Analog(DAC) converter output of the microcontroller
LM329(? voltage regulator): op-amp (opposite amplifier) based comparator. National Semiconductor Corporation(USA)
Professional comparators: LM339, LM393
Comparators: LM324, LM358, , TL081/2/3/4, OP07, OP27
μA741
Nonlinear current change
Nonlinear magnetism change
Nonlinear current change

11. Current transformer connections and circuitry
External interrupts: a series of pulses(50Hz) sent to microcontroller
Power need: single +5V DC.
Peak voltage: 2V (when load current is 10A)
Resistor: 120 Ω
Voltage shifted up: 2.5V (avoid negative voltage at the input of the comparator)
Coil inductance
+2.5V

12. Detect the status of an appliance
Detection software: continuously evaluate whether the load is active or not
Interrupt: every 500ms
Active: 10 external interrupts occur within 500ms.
External interrupt
Receive timer generated interrupt
Count numbers of current pulses
If number of current pulses
is greater than 10
Set activity variable high
Set activity variable low
Restart the timer and clear the current pulses count

13. Design of the Central Controller Unit(CCU)
Similar to the SU(Sensor Unit)
LED: 1 indicate the power to the CCU is on
2 show that the CCU is in transmit mode
3 indicate that the CCU is in receive mode
RS232: bauds (115200bps)

14. Radio Frequency Communication protocol
All the sensor units communicate with the central controller unit on the same frequency
Method: the sensors will respond only when told to do so. PC
PC requests data from a particular sensor
PC receives the data from the specified sensor
Central Unit
Controller initializes the particular sensor
Controller interprets the data and relays it to the PC
Sensor Unit
Sensor responds with the activity data

15. Radio frequency communication packets
RF communication packet sent by the controller:
RF communication packet sent by the sensor unit:
Start byte ID byte end byte
Start byte ID byte activity byte end byte
Description
Hex Value
Binary Value
Start byte
0x55
End byte
0x6C
ID byte: 1
0x63
ID byte: 2
0x33
ID byte: 3
0x36
ID byte: 4
0x3A
Activity byte: active
0x53
Activity byte: inactive
0x69

16. conclusion
This paper presented the design of a Selective Activity Monitoring system and the applied research into the implementation issues.
completely fabricated system
the sensor unit