REMOTE CONTROL OF DEVICES USING CELLPHONES
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.
IC 4017 DECADE COUNTER
+Vcc
Q5
Q5
Q1
1
16
Q1
R
2
15
RESET
14
CLOCK
Q2
Q0
3
Q2
4
Q6
5
Q7
6
Q3
7
GND
8
Q0
Q6
CK
CE
C0
Q7
Q3
Q9
Q4
Q8
13
12
11
CLOCK ENABLE
COUT
Q9
10
Q4
9
Q8
RING COUNTER SECTION
RESET SWITCH
+5 V
S1
16
15
14
CLOCK INPUT from
Schmitt Trigger
SWITCHING SECTION
R1
IC1
4017
D1
+12V
3 Q0
2 Q1
4 Q2
7 Q3
10 Q4
1 Q5
5 Q6
6 Q7
9 Q8
11 Q9
To Telephone Line
RLC1
D2
LE
D
R5
N/O
N/C
TR1
R4
TR2
R2
R3
13
8
CIRUIT DIAGRAM OF RING COUNTER CUM SWITCHING & CONTROLLING UNIT
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
STATE OF D INPUT CLOCKED
TO Q OUTPUT ON RISING
CLOCK EDGE
TRANSIENT
DATA
D
Q
CLOCK
SINCE LAST POSITIVE GOING CLOCK
DATA HELD IN LATCH
CLOCK
FIG 3
Timing diagram
D INPUT
1
0
CLOCK INPUT
1
0
Q OUTPUT
1
0
1
Q OUTPUT
0
TIME
FIG 4
IC 4013
14
13
VCC
Q2
Q1
IN.Q1
1
D.CHAR
12
IN.Q2
CLK1
2
3
THERS C.VTG
11
10
9
8
CLK2
RST2
D2
SET2
RST1
4
RST 1
D1
5
O/P1
SET1
GROUND
6
7
TRGER GROUND
CIRCUIT DIAGRAM
+5V
+5V
N/O
+12
V
IC3
Sw
1
N/C
9
5
Input
signlas
4
3
1
IC1A
13
10
2
N/O
14
9
11
1
6
1
IC1B
15
2
7 12
Q1
N/C
3
14
4
13
5
1
2
6
11
8
6
Q2
Q3
+5V
Q4
5
4
3
1
IC2A
9
Q
10
2
Q
11
R1
13
7
IC2B
8
7 12
GND
6
10
0
14
8
N/O
N/O
N/O
N/C
N/C
N/C
RL
1
to
Telephone
Line
RL
2
RL
3
RL
4
POWER SUPPLY UNIT
IC1
7812
IC1
7805
D1
1
+12V
9V
+5V
230AC
C1
D2
1
X
1
C2
C3
C4
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.