Mini-Project Challenge , Electrical Engineering Association , 2014-15
Controlling Home Appliances using Remote Control
Submitted by
1. Amit Kumar Singh : 132202 , B.Tech 2/4 , EEE
amitkumarsingh1201@gmail.com
2. Ankit Agrawal : 132203 , B.Tech 2/4 , EEE
ankitagrawal613@gmail.com
3. Shashi Ranjan : 132253 , B.Tech 2/4 , EEE
shashikr7387@gmail.com
4. Santi Bhusan Acharya ; 132251 , B.Tech 2/4 , EEE
bhusan841325@gmail.com
Objective :
Controlling home appliances using remote control which can be further commercialized
Apparatus Used :
1. Encoder IC ( HT12D)
2. Decoder IC (HT12E)
3. Arduino Board
4. Voltage Regulator (IC7805)
5. ASK RF Transmitter
6. ASK RF Receiver
7. Battery ( 9 V)
8. LEDs
9. NPN Transistor ( CL100)
10. Relay Switch ( SPDT)
11. Resisters (39 K , 1 M , 1K , 500 K )
12. Antenna
13. Switches
14. Connecting Wires
15. Bread Board
Circuit Descriptions :
Encoder and Decoder :
HT12D and HT12E have operating voltage of 2.4V to 12V . They are both CMOS ICs.
HT12E has 8 address and another 4 address / data lines . Data set on these 12 pins are
serially transmitted when the TE ( Transmission Enable) pin taken from HIGH to
LOW . Data appears serially at Dout . This data is transmitted 4 times in succession .
15 and 16 pins used to set this oscillation frequency and it is only the R value in the RC
time constant . The C is internally built . We need to set the resistance in these pins and
that will determine the frequency .
The internal oscillation frequency of the decoder is 50 times the oscillator frequency of
the encoder IC . So account to this , we have to choose R values . In our project , we have
chosen R=1 M and RD = 39 K .
DOut is given to a transmitter module , which transmits the data and at receiver end ,
antenna picks it and it goes to Din 14 pin and if address matches , then only Dout occurs
( i.e. LED glows ) . It can also be seen by valid transmission (VT (17) ) pin . If the
address pins are matched 4 times in succession , the VT pin goes high.
We are transmitting the data by 433 MHz ASK RF Transmitter and Receiver module . In
these modules digital data is represented by different amplitude of the carrier wave ;
hence this modulation is known as Amplitude Shift Keying (ASK) . Rf transmission is
more strong and reliable than IR transmission due to following reasons :
RF signals can travel longer distances than IR ;
Only line of sight communication is possible through IR while RF signals can be
transmitted even when there is any obstacle ;
IR signals will get interfered by other IR sources , but signals on one frequency
band in RF will not interfered by other RF signals .
Relay Switch :
It is an electrically operated switch used in electromagnet to mechanically operate the
switch . When the electricity is applied to V1 and V2 , the electromagnets acts upon the
SPDT ( Single Pole Double Through ) switch , so that the R and C terminals are
connected . When the electricity is connected , then the A & C terminals are connected .
7805 Voltage Regulator :
It is an integrated circuit , It is a number of 78XX series of fixed linear voltage regulator
ICs . The XX in 78XX indicates the fixed operating voltage 7805 provides 5V regulated
power supply .
Working :
Transmitter Section / Remote Section :
It consists of an encoder (HT12E) 8 - bit address and 4-bit data . Address pin can be
connected to GND or left open .States of these address pins should be mattered with a
status of address pin in the receiver for the transmission of data . Whenever we press any
key in remote , the encoder generates corresponding 4-bit data and send these data with
8-bit address by using ASK transmitter . The transmitting frequency is 433 MHz . Data
will be transmitted only when the Transmit Enable pin (TE) is LOW . 1M resistor will
provide the necessary external resistance for the operation of the internal oscillator of
HT12E .
Receiver Section :
ASK RF receiver receives the data transmitted using RF Transmitter . HT12D decoder
will convert the received serial data to 4- bit parallel data D0 - D3 . The address pin A0 A3 should match with a status of address pin of the HT12E at the transmitter for
transmission of the data . LED connected to the above circuit becomes LOW when valid
transmission occurs from transmitter to receiver . 39 K resistor will provide the
necessary resistance required for the internal oscillator of the HT12D .
Each output pins are connected to the arduino board . Its code is written in such a way
that when ever switch is pressed , it toggles the state of its output pins ( LED pins) . This
output signal is not capable to drive a relay directly (i.e. connected to D0 pin ) . So , we
are using current driver ( SL100 ) . The appliance is connected to 230 V AC through the
relay . The relay will be energized or re-energized when switch is pressed .
Merits and Applications :
1. Controlling Home appliances from a wide range( ~100 meter )
2. Electric Power wastage can be minimized
3. Easily accessible
4. Low cost to implement ; can be commercialized
5. Portable
6. It extends opportunities to implement photo diodes , image processing applications in
further advanced projects ( i.e. Lights will automatically glow when the system detects
human beings)
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