Cedric

Name Student no. Level Course Topic Department Mentor Institution Due date

S.Ntsethe 20501401 S4 N.DIP.Electrical Engineering Timed Isolator Electrical Engineering C. Rutters M.U.T 22august 2008

1

TABLE OF CONTENTS TOPIC

PAGE NO.

INTRODUCTION

3

PROJECT OBJECTIVES

4

BACK GROUND

5

BLOCK DIAGRAM

6

EXPLANATION OF BLOCK DIAGRAM

7

SCHEMATIC DIAGRAM

6

PRINCIPLE OF OPERATION

7

PRICE LIST

8

PROJOCT TIME PLANNING

9

CONCLUSION

10

REFERENCES

11

INTRODUCTION A Timed Isolator is designed to provide automatic safety isolation of an appliance after a preset period. The purpose of this design, outlined here, is to provide power to the appliance 2

for just the necessary amount of time. We are going to incorporate a PIC16F84, switches as push buttons and LED’s for status. Isolation is double-pole, i.e. both live and neutral. Maximum loads with the standard design are limited by the relay. Use of a contactor extends capability to a full 13A load with inductive content, e.g. a tumble dryer, or washing machine. The technique for providing isolation for a signal source utilizing two or more modulators is described. In particular, the project generates a timed sequence by means of a PIC16F84 that is synchronized to the data signal which permits transmission in a forward direction, and which attenuates a reverse direction signal. Another embodiment attenuates primarily reflected light signals by utilizing a passive waveguide and a modulator. The passive waveguide provides a propagation delay such that signals reflected from its end facet are attenuated by the modulator. This apparatus is suitable for use as an isolator for a light source in a high-speed optical fiber data transmission system

There are 5 LEDs that are connected to the PIC16F84 as output devices. They will be having different delays, which will be set using PIC 16F84.This feature is quite deliberate and improves tamper proofing of the system. The project also presents an opportunity to provide MCB (Miniature Circuit Breaker) or better still RCD (Residual Current Device) protection to the appliance.

BACKGROUND When several optical components are connected in tandem, an optical isolator is usually required to suppress instability of the optical source. Such instability may be caused by light reflected back into the optical source by a neighboring component, or by light originating from a different source that impinges on the optical source.

3

Prior art optical isolators typically rely on the non-reciprocal nature of magnetic media to achieve isolation. These current devices rely on a polarization rotation or non-reciprocal beam deflection, and with time invariant systems this non-reciprocal behavior is required by definition. Other approaches, such as using a linear polarizer in conjunction with polarization components that function as quarter-wave plates, require that the reflection being isolated against is a non-polarization-changing reflection. Therefore, if the reflected signal is in an arbitrary polarization state, the reciprocal isolation means discussed above are inadequate. Further, interfering light from a different source may have an arbitrary polarization state. Thus, any time-invariant reciprocal means cannot in general provide isolation. It is known that directly modulated semiconductor laser sources suffer from frequency chirp problems due to the inherent fluctuations of the complex index of refraction that are used to induce the modulation. Semiconductor electro absorption modulators using bulk or quantum well structures have been developed to mitigate such frequency chirp problems, and monolithically integrated devices comprising electro absorption modulators and distributed feedback lasers (DFB lasers) or distributed Bragg reflector lasers (DBR lasers) have been demonstrated See, for example, Y. Noda et al., "High-Speed Electro absorption Modulator with Strip-Loaded GaInAsP Planar Waveguide", IEEE J. Lightwave Tech., Vol. LT-4, pages 1445-53 (1986), and M. Suzuki et al., "Monolithic Integration of InGaAs/InP Distributed Feedback Laser and Electro absorption Modulator by Vapor Phase Epitaxy", IEEE J. Lightwave Tech., Vol. LT-5, pages 1279-85 (1987). For very high bit rate systems of 10 Gigabits per second or higher, however, even the small amount of frequency chirp exhibited by a monolithically integrated laser

BLOCK DIAGRAM

4

LEDs

POWER SUPPLY

SWITCH PIC

RELAY

Figure 1

BLOCK DIAGRAM

A DC power supply powers the switches, the relay and the PIC The LEDs that are connected to the PIC serves as output devices.

SCHEMATIC DIAGRAM

5

U2 7805 VI

VO

3

U1

GND

1

2

C4

16 15

R7

C3

1nF

4

1nF

OSC1/CLKIN OSC2/CLKOUT MCLR

RA0 RA1 RA2 RA3 RA4/T0CKI

10k

B1

RB0/INT RB1 RB2 RB3 RB4 RB5 RB6 RB7

C1

12V

100n

X1 CRYSTAL

C2

17 18 1 2 3 6 7 8 9 10 11 12 13

R8

D1

10k

D2

R1 R2 R3 10k R4 10k R5 10k R6 10k

LED D3 LED

10k 10k

D4

LED

PIC16F84A

100n

LED D5

D6 LED LED

RL1 Q1 2N3905 G2R-24-DC12

Figure2 SCHEMATIC DIAGRAM

PRINCIPLE OF OPERATION

6

Refer to figure2, PortA bit0 and bit1 are configured as inputs and PortB, bit0, 1,2 and 3 are configured as outputs. When one presses switch 1, which acts as a start button, it sends an input signal to PortA bit0 of the PIC16F84. This causes the LED on PortB, bit0 to go high, taking 10ms. When the first LED turns off, the second one on PortB bit1 will go high, taking 1 second, the third LED will light for one minute. When the last LED goes high, it sends a signal to the transistor,,,,,,,,,,,,,,,,,,,,,. Pressing switch1 stops the operation of the circuit. In practice, this project may need a sensor. The sensor can work like this, say one is using a washing machine, as soon as one stops using it, the sensor will detect that change.

PART LIST

7

RESISTORS 2. R2, R3, R4, R5,R8 & R6 (A220k) R7 CAPACITOR 8. C4 &C3 C1 &C2 SEMICONDUCTOR 17. TR1 21. LED1,2,3,4,5 &6 MISCELLANEOUS 23.RLAI 26. BI REG 27. SW1 CRYSTAL PIC16F84 30. P5, P6, P7, P8, P9 & P10 TOTAL

UNIT PRICE R1.25 R1,00

R0.60 R0,50

R8.00 R1.00 R12.45 R5.00 R0,90 R5.00 R1,00 R45,00 R25.00 R160.00

PROJECT TIME PLANNING ACTIVITY Topic research Research information Schematic Drawing Component quotations Proposal writing

PLANNEDTIME(In days) 6 days 4 days 2 days 1 day 9 days

ACTUAL TIME(In days) 7 days 4 days 3 days 2days 10days

8

EXPECTED RESULTS In this project we expect that, this design should provide power to appliances for just the necessary time. For example, after using our washing machine it automatically switches off but the main power supply is still on. It has the maximum delay of 4 to 8 hours.

CONCLUSION This project provide automatic safely after preset period using the PIC 16F84, its inputs are switches and outputs are LED. The project also presents an opportunity to provide Miniature circuit Breaker or better still Residual current device protection to the appliances.

9

REFERENCE  ELECTRONICS TODAY INTERNATIONAL  INTERNET

10

11