REMOTE CONTROL OF DEVICES USING CELLPHONESREMOTE CONTROL OF DEVICES USING CELLPHONES

Shuhab-u-Tariq (1SI03EC109)Shuhab-u-Tariq (1SI03EC109)

INTRODUCTION

Telephone operated device control circuit which enables switching ON & OFF of appliances through telephone lines.

It senses the telephone ring. Automatically switches call to this system, after

pre-defined rings. Switches ON/OFF the load depending upon the

key pressed by the caller.

BASIC BLOCK DIAGRAM

RING DETECTOR & SCHMITT TRIGGER SECTION

RING COUNTER CUM SWITCHING UNIT

This Section counts the number of rings and lifts the cradle automatically after pre-defined number of rings.

IC 4017 is used to count the number of rings.

The triggering action is carried out by relay driver circuit, which comprises of two Darlington transistors with a relay.

Q1

Q2

Q6

Q3

RESET

CLOCK

CLOCK ENABLE

COUT

Q9

Q4

Q8

Q7

Q4

Q9

C0

Q0

Q5

R

CK

CE

Q8

+Vcc

Q5

Q1

Q0

Q2

Q6

Q7

Q3

IC 4017 DECADE COUNTER

11

9

12

13

14

15

16

8

7

6

5

4

3

2

1

10

GND

CIRUIT DIAGRAM OF RING COUNTER CUM SWITCHING & CONTROLLING UNIT

3 Q0

2 Q1

4 Q2

7 Q3

10 Q4

1 Q5

5 Q6

6 Q7

9 Q8

11 Q9

R2

R3

R1

16

IC1 4017

15

13

14

S1

+5 V

CLOCK INPUT fromSchmitt Trigger

RESET SWITCH

D1

8

TR1

R4

TR2

N/O

N/C

+12V

RLC1

R5

D2

LED

To Telephone Line

RING COUNTER SECTION SWITCHING SECTION

DTMF DECODER & BCD TO BINARY CONVERTER MODULE

• DTMF – Dual Tone Multiple Frequency

Resultant signal of two tones at the same time for any key pressed

f(t) = Asin(2*П*fa*t) + Bsin(2*П*fb*t)

Pin Diagram of MT8870

Pin Diagram of IC 74154

DTMF to Binary converter

Function Decode Table

LATCH & LOAD DRIVER SECTION

This section executes the command send by caller by latching the load to previous state on/off.

Terms and components used here: D flip-flop - It is incorporated in IC4013 2003-driver IC- High voltage and high current driver IC is used to drive low impedance relay.

D flip flop an overview

D Q

CLOCK

CLOCK

TRANSIENTDATA

SINCE LAST POSITIVE GOING CLOCK DATA HELD IN LATCH

STATE OF D INPUT CLOCKED TO Q OUTPUT ON RISING CLOCK EDGE

FIG 3

Timing diagram

0

1

0

1

0

1

0

1

D INPUT

CLOCK INPUT

Q OUTPUT

Q OUTPUT

TIME

FIG 4

IC 4013

VCC Q2 IN.Q2 CLK2 RST2 D2 SET2

Q1 IN.Q1 CLK1 RST1 D1 SET1 GROUND

D.CHAR THERS C.VTG RST 1 O/P1 TRGER GROUND

14 13 12 11 10 9 8

1 2 3 4 5 6 7

CIRCUIT DIAGRAM

Q1

Q2

149 13

11 12

IC1B

86

7

IC3

2

1

4

3

8

9

5

15

16

13

12

6 11

14

7

100

GND

5 1

3 2

IC1A4 10

149 13

11 12

IC2B

86

7 Q

Q5 1

3 2

IC2A4 10

R1

+5V+12V

N/O

N/C

N/O

N/C

+5V

Sw1

+5V

RL1

N/O

N/C

RL2

N/O

N/C

RL3

N/O

N/C

RL4

to Telephone

Line

Q3

Q4

Input signlas

POWER SUPPLY UNIT

230AC

X1

C1

D21

C2 C3

IC17812

D11

9V

C4

IC17805

+12V

+5V

CONCLUSION

Low power consumption, and compact in size.

From any distance appliances can be controlled, overcoming the limited range of infra-red and radio remote control.

High reliability, due to the usage of semi conductors.