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MULTIPLE DEVICE CONTROLLER
Abstract- Dual tone multi-frequency
signaling (DTM F) is used fortelecommunication
signalingover analog telephone lines in the voice-
frequency band betweentelephonehandsets and
other communications devices and theswitching
center. DTMF technique can be used for
controll ing appli ances together via powerl ine.
Keywords-Dtmf , powerli ne, encoder, decoder
1. INTRODUCTION
Using this simple circuit you can switch on or off
upto 8 appliances remotedly via the mains line. 4 bit
dual tone multi frequency (dtmf) data is send through
the mains line to switch on or off the desired
appliances via 8 relays.
Push to on/off toggle switches S1 through S8 are
used to control appliances. If any switch is in UP
position, the encoder sends off signal data and the
respective output goes low in the decoder. If the
switch is in down position, the encoder sends on
signal data and respective output goes high to
become latched.
Eight 4 bit data words (0000-0111) are used to switch
off 8 appliances. Another eight 4 bit words (1000-
1111) are to switch on the appliances. If D bit (MSB)
is high it is on signal, and if D bit is low it is off
signal. Once switches have been set in on or off
position, data words are automatically sent
continuously.
In case the power fails, power-on-relay set works and
all the outputs of IC CD4099 (IC8) go low to switch
off all the relays. However, when the power resumes,
data is sent automatically again and the respective
relay energise. So even after power failure correct
devices are switched on/off automatically once the
power resumes.
The circuit comprises of two units,namely,a DTMF
encoderat the controlling end and DTMF decoder at
the other end where the appliances are located. The 2
units are connected via phase(L), neutral(N) and
earth(E) wires of the AC mains line,with the AC
phase being the same.
2.HARDWARE
2.1 ENCODER
The encoder circuit comprises DTMF tone generator
IC UM9089(IC2), dual binary counter IC
CD4520(IC3), and 2 16 channel multiplexer ICs
CD4067(IC4,IC5).
The main frequency 50HZ is fed to pin 2 of dual
binary counter IC3(A) via transformer X1 secondary.
The D output (MSB) of IC3(A) is connected to strobe
pin 10 of IC3(B). The 4 bit binary output of IC3(B) is
fed to the 2 16-channel multiplexer as address input.
The 16 decoded outputs of IC4 are connected to the
columns pins of the DTMF tone generator,while the
outputs of IC5 are connected via switches S1 through
S8 to the row pins of IC2. Inputs Y0 to Y15 of IC5
are connected to switches S1 to S8.
DTMF tone generator IC2 has 4 row pins and 4
columns pin, each of which is associated with a
specific frequency. When any row pin is shorted to
any column pin, the associated dual frequency tone is
generated. At any given instant of a row and column
takes place as per address present at pin 10 thorugh
14 of IC4 IC5 and the position of switch s1 through
S8. The selected column is connected to the selected
row via pin 1 of IC4 and IC5. A total of 16 dual
frequency tones, 1 for each combination are thus
possible. The output of IC2 are indicated by glowing
of RED LED. For each count, one row and one
column is connected together via IC4 and IC5 and
dual tone generator and superiposed on the neutral
mains.
Fi 1. Encoder Unit
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2.2 DECODER
It comprises of MT8870, DTMF receiver(IC7),
CD4099 8-bit addressable latch IC8, and relay
drivers.
DTMF tone generated by the coder and transmitted
through mains wires is received DTMF to binary
decoder IC7 for conversion into its corresponding
four bit output at pin 11 through 14. This output is
fed to IC8.
If D bit is high, one of the output of IC8 goes highand it latches. If D bit is low, one of the output of IC8
will go low. The Qo to Q7 outputs of latch IC8 are
fed to, via 1k resisitors, transistors T2 through T9 for
driving relays RL1 through RL8 to switch on/off the
selected device.
3. COMPONENT LIST
IC1,IC6- +5V 7805 REGULATOR IC IC2- UM95089 DTMF tone generator IC3- CD4520 DUAL binary counter IC4,IC5- CD4067 16 CHANNEL
multiplexer,demultiplexer
IC7- MT8870 DTMF receiver IC8- CD4099 8-bit addressable latch D1-D12- 1N4007 rectifier diodes
230V AC
50 Hz
DTMF
DECODER(RECIEVER)
8 BIT
ADDRESSABLELATCH
RELAY DRIVERSOUTPUT
APPLIANCES
Fig 3 . Decoder unit
Fig 2. Encoder Circuit Diagram
Fig 4. Decoder Circuit Diagram
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LED- 5mm red LED T1-T9- BC548 npn transistor Resistors (R1 to R16) Capacitors (C1 to C9) RL1-RL8- 9V,15O ohm,1C/O relays S1-S8- push to on/off switch X1-X2-230V AC Primary to 9V-0-9V,
500mA secondary transformers
XTAL1,XTAL2-3.5795MHz crystal
4.WORKING
Using the keyboard mounted on the coders panel,
you can easily switch on/off the desied appliances.
The on/off position of switches on the keyboard
indicated whether the renote appliance is on or off.
Lets assume you want to switch on appliance no. 4
and 8 connected across RL4 and RL8. When you
push down switch S4 and S8 to down position, these
produces 1011 and 1111. This encoded data is
superimposed to mains neutral via capacitor C1.
After receiving this data, IC7 places the data on its
output as well as at input of IC8. Since the output D
input (PIN3) of IC8 is high, its Q3 and Q7 outputs
go high and latch. As a result, relays RL4 and RL8
energise to turn on appliance no.4 and no.8. All other
outputs will be low, keeping the remaining6
appliances are off.
When IC7 receives data, its delayed steering output
goes high and transistor T1 conducts to make pin4 of
IC8 low. This enables IC8 to receive data.
5. APPLICATIONS
Can be used as switching device in :-
(i)Industries where many devices are to be controlled
simultaneously.
(ii)Home appliances.
6. FUTURE SCOPE
DTMF Technique can be used by HomeAutomation system.
Remote control system. Number of appliances can be increased.
7.CONCLUSION
Thus, this technique can be used to access multiple
things at a time and help in consuming time in this so
busy world.
8. Acknowledgment
We would like to thank our department for
encouraging us to search on this topic and also our
H.O.D and all the staff members for their continuous
support and help.
9. REFERENCES
Electronics For You Magazine Electrical Contribution & Distribution
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