1. REMOTE CONTROL OF DEVICES USING CELLPHONES
Shuhab-u-Tariq (1SI03EC109)

2. 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.

3. BASIC BLOCK DIAGRAM

4. RING DETECTOR & SCHMITT TRIGGER SECTION

6. 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.

7. IC 4017 DECADE COUNTER Q1 Q2 Q6 RESET CLOCK Q7 Q5 11 9 12 13 14 15 16
CLOCK ENABLE
COUT Q9 Q4 Q8 Q7 C0 Q0 Q5 R CK CE
+Vcc
IC 4017 DECADE COUNTER 11 9 12 13 14 15 16 8 7 6 5 4 3 2 1 10
GND

8. 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 from
Schmitt 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
CIRUIT DIAGRAM OF RING COUNTER CUM SWITCHING & CONTROLLING UNIT

9. 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)

11. Pin Diagram of MT8870

12. Pin Diagram of IC 74154

13. DTMF to Binary converter

14. Function Decode Table

15. 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.

16. D flip flop an overview
D Q
CLOCK
TRANSIENT
DATA
SINCE LAST POSITIVE GOING CLOCK DATA HELD IN LATCH
STATE OF D INPUT CLOCKED TO Q OUTPUT ON RISING CLOCK EDGE
FIG 3

17. Timing diagram 1
D INPUT
CLOCK INPUT
Q OUTPUT
TIME
FIG 4

18. IC 4013
VCC Q IN.Q2 CLK2 RST D SET2
Q IN.Q CLK1 RST D SET GROUND
D.CHAR THERS C.VTG RST O/P TRGER GROUND

19. CIRCUIT DIAGRAM Sw1 Q1 Q2 Q3 Q4 IC3 RL1 RL2 RL3 RL4 to Telephone Line14 9 13 11 12
IC1B 8 6 7
IC3 2 1 4 3 5 15 16
100
GND
IC1A 10
IC2B Q
IC2A R1
+5V
+12V
N/O
N/C
Sw1
RL1
RL2
RL3
RL4
to Telephone Line Q3 Q4
Input signlas

20. POWER SUPPLY UNIT X 1 +12V 9V +5V 230AC C1 C2 C3 C4 IC1 7812 7805 D11

21. 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.