DEPARTMENT OF ELECTRICAL & INFORMATION ENGINEERING PROJECT PRESENTATION

Transcription

1 DEPARTMENT OF ELECTRICAL & INFORMATION ENGINEERING PROJECT PRESENTATION PROJECT TITLE: ELECTRONIC CHILD MONITORING DEVICE By: Supervised By: Examined By: PROJECT NO.: PRJ 091 OKOTH JOHN AKUMU REG. NO.: F17/2132/2004 Dr. Vitalis K. Oduol Dr. M. Gakuru May,

2 Presentation Outline A Brief of Radio Frequency Overview of the System Design and analysis Results, Conclusion and further work Distance Measuring Distance measuring was the primary focus of this project. The Received Signal Strength Indicator (RSSI) from the receiver module was used to determine this distance by implementing a counter circuit. 2

3 Imagine if You didn t have to worry about the whereabouts of your child wherever you are (soccer stadium, a conference hall, church), knowing they are safe and secure. All this was possible at a relatively cheap cost. Just two small devices; one on you and the other on the young one can solve all your worries. The future for this generation parenting is on the Electronic Child Tether. 3

4 RF in Brief. An antenna is a component that radiates and receives the Radio Frequency or microwave power. It is a reciprocal device and the same antenna can serve as a receiving or transmitting device. They provide transitions between guided and free-space waves and is a key component in any wireless system. A receiver picks up the modulated carrier signal from its antenna. The carrier signal is downconverted, and the modulating signal (information) is recovered. The receiver is used to process the incoming signal into useful information, adding minimal distortion. A transmitter is an important subsystem in a wireless system. In any active wireless system, a signal will be generated and transmitted through an antenna. The signal s generating system is called a transmitter. A transmitter can be combined with a receiver to form a transceiver. In this case, a duplexer is used to separate the transmitting and receiving signals. 4

5 System Overview The Wireless Tether System will: Utilize RF signals (~2.4 GHz) to communicate between the child and parent module. Have a response time of no more than 1 second; the response time being the time for the parent device to decode the incoming signal and make a determination as to the condition of the child device. Have a variable signal strength threshold to vary the allowable separation of the child device. Operate a simple LED display to report the general direction of the child device. Have an audio/vibration warning system that warns the parent of an event with the child device (i.e. too far away or loss of signal). Utilize batteries as power supply and have an LED to show the amount of power and warn the parent. 5

6 The signal is acquired from the child device through the antenna. The conditioning process consists of amplifying the signal, filtering the desired frequencies, and demodulating the signal. The output from this stage will be a clean signal that the signal processing stage will be able to interpret. receive the conditioned signal as input, process the data contained in the signal, and generate an appropriate signal for the output devices i.e. the buzzer and the LEDs. decode the signal from the signal processing stage and actuate an audible alarm or direction LED s. 6

7 Parent device block diagram Status LEDS Direction al LEDs Omnidirection al antenna Antenna switchin g circuitry Antenna switching control RF modul e TX data R X RSS I PIC Microcontroller ADC ADC LED circuitry Speaker circuitry circuitry Sensitivity Control Alarm off Button Panic Button Detect mode/ directional mode switch ON/OFF switch Power supply 7

8 Child Device Block Diagram Antenna PIC Microcontroller RF module TX RSSI ADC Speaker circuitry circuitry RX ON/OFF switch Power supply 8

9 Design and Analysis A counter circuit was developed using the theory of a TIC Two signal are required for this circuit The first signal received by the parent device starts the counting The second signal received by the parent device stops the count 9

10 The distance was determined by calculating the time that the RF signal will take in flight. (TOF) Reset the counter. Send request from child module to the parent module. Start the counter immediately the first signal is received by the parent. Send a signal back to the child module. Child sends a second request. Stop the counter immediately the second signal is received by the parent and take its reading. 10

11 Diagram of distance between the child and the parent Antenna Antenna Child Transceiver (TX/RX) Free Space Parent Transceiver (TX/RX) d = distance The distance between the two devices, the receiver and the transmitter can be calculated as Where c is the speed of light and tr is the time of flight Between the parent and the child twice. 11

12 12 TIME ACQUISITION CIRCUIT 74LS273 MR CP D7 D6 D5 D4 D3 D2 D1 D0 Q7 Q6 Q5 Q4 Q3 Q0 74LS193 CPU CPD PL MR D3 D2 D1 D0 TCU TCD Q3 Q0 74LS163 CEP CET CP PE D3 D2 D1 D0 MR TC Q3 Q0 74LS163 CEP CET CP PE D3 D2 D1 D0 MR TC Q3 Q0 74LS273 MR CP D7 D6 D5 D4 D3 D2 D1 D0 Q7 Q6 Q5 Q4 Q3 Q0 74LS193 CPU CPD PL MR D3 D2 D1 D0 TCU TCD Q3 Q0 74LS193 CPU CPD PL MR D3 D2 D1 D0 TCU TCD Q3 Q0 74LS193 CPU CPD PL MR D3 D2 D1 D0 TCU TCD Q3 Q0 74LS193 CPU CPD PL MR D3 D2 D1 D0 TCU TCD Q3 Q0 +V 5V S1 CP1 CP2 +V 5V 74LS47 A3 A2 A1 A0 test RBI g f e d c b a RBO U8 abcdefg. V+ abcdefg. V+ 74LS47 A3 A2 A1 A0 test RBI g f e d c b a RBO U7 74LS47 A3 A2 A1 A0 test RBI g f e d c b a RBO U3 abcdefg. V+ abcdefg. V+ 74LS47 A3 A2 A1 A0 test RBI g f e d c b a RBO U6 74LS74 CP1 D1 S1 R1 CP2 D2 S2 R2 R1 1k

13 Circuit overview Clock Consists of a clock, to initiate the counts Switch- activates the two signals to be received Counters To give the counts Display Displays the amount of counts from the counter hence time. Register Data held at the registers after the counters are cleared ready to be sent to the computer for analysis. 13

14 The distance calculation on a software platform- Visual Basic The circuit would be linked to the computer via the parallel port 14

15 Time, (ns) Distance, d (m)

16 At ns d = 0.5 x x 10-9 x 3x 10 8 = m 16

17 Electrical specifications Device Property Minimum Typical Maximum Transmitter/ Input Voltage(V) Receiver Supply Current(mA) Sleep Current(uA) Power Consumption Microcontroller Input Voltage (V) Supply Current (ma) Sleep Current (ua) Current Sunk By any I/O pin (ma) Power Consumption (W) Antennas Power Consumption (W) Buzzer Input Voltage (V) Supply Current (ma)

18 Physical Specifications The two devices should be as small as possible (the size of a normally sized phone i.e. motorola w220). Child device size is very important since he should be as comfortable as possible and to avoid loosing it. Smooth surfaces. Attachment to the body. Should be buckled at the belt. 18

19 Conclusion and Recommendations The child tether applies RF technology to introduce a reliable dimension of childminding anywhere. It provides constant awareness of children with the integration of reliable and cheap technology. RF modules are implemented into this system to provide a reliable location method. Communication between the network of RF modules will constantly monitor the location of the child. The device to be built in the future for commercial production would have the following features: Detect extreme temperatures in surroundings and notify parent if it is determined that potential danger exists. Educate children about potentially dangerous household areas. Provide a two-way phone quality voice communication. 19

20 Thank you. END 20