DTMF based Home Automation System

TRAINING REPORT
OF
SIX WEEKS INDUSTRIAL TRAINING,
UNDERTAKEN
AT
APPIN TECHNOLOGY LAB
ON
EMBEDDED SYSTEMS
SUBMITTED IN PARTIAL FULFILLMENT OF THE DEGREE
(Bachelor of Engineering- ECE- 2012)
Under the Guidance of: Submitted By:
Name: Paras Khanna Name: Daksh Raj Chopra
Department: University Roll No.:B120020081
__________________________________________________________
Chitkara University, Himachal Pradesh.

ACKNOWLEGMENT
I take this opportunity to express my profound gratitude and deep regards to my guide Ravi
Sir for his exemplary guidance, monitoring and constant encouragement throughout the
course of this thesis. The blessing, help and guidance given by him time to time shall carry
me a long way in the journey of life on which I am about to embark.
I also take this opportunity to express a deep sense of gratitude to Paras Khanna, , Appin
Technology Lab for his cordial support, valuable information and guidance, which helped me
in completing this task through various stages.
I am obliged to staff members of Appin Technology Lab for the valuable information
provided by them in their respective fields. I am grateful for their cooperation during the
period of my assignment.
Lastly, I thank almighty, my parents, brother, sisters and friends for their constant
encouragement without which this assignment would not be possible.

PREFACE
There is a famous saying “The theory without practical is lame and practical without theory is
blind.”
This project is the result of six weeks training at Appin Technology Lab. Summer training is
an integral part of “Engineering” course and it aims at providing a first-hand
experience of industry to students. This practical experience helps the students to view the
industrial work and knowledge closely. I was really fortunate of getting an opportunity to
pursue my Summer Training in reputed, well established,fastgrowingandprofessionallymanaged
organizationlikeAppinTechnologyLab assigned “DTMF Controlled Home Automation
System Using 8051.”

TABLE OF CONTENTS
S. No. Contents Page No.
1. Company Profile…………………………………………………..1
2. Project Undertaken………………………………………………...2
3. Introduction to Project……………………………………………..3
4. Modular description………………………………………………..4
5. Design……………………………………………………………...5
6. Coding……………………………………………………………..6
7. Test cases……………………………………………………….....7
8. Industry Application……………………………………………....8
9. Future Enhancements……………………………………………....9
10.Data Sheets…………………………………………………………10

I. Company Profile
II. Project Undertaken
I chose the project of DTMF controlled home appliance system. The main aim of the project
is to operate the any home appliances by using an IR remote which is interfaced with the
microcontroller. IR remote acts as the transmitter in this project. When a button is
pressed in the remote, the signal will be passed and received by the IR
receiver TSOP Receiver. This signal is sent to the microcontroller which decodes
the signal and performs the corresponding action in accordance with the button
pressed in the remote. For example, if number 1 is pressed in the remote, the load
will be switched on/offaccording to the user requirement.
The need for the above project was that this project firstly it saves our time. If you are stuck
in traffic you can switch on your microwave oven on slow cooking mode. By the time you
reach your home your food will be ready. You don’t have go to each room to check whether
the lights are on/off. You can do with a click of single button. Secondly, it save our money in
the long run. There are some appliances like a television which we switch off but not its
power supply. There is a Led still glowing in it which uses electricity. If we have this
television attached to our project then we can switch off its power supply whenever we want
and there are many other devices like this. Thirdly, it for self-maintenance and security.
Security as in if we by chance forgot to switch off any of lights then we can switch off from
our phones. Lastly, we all know that all this will make our life easy and trouble free.
Industrial applications for the project made are that one can control home appliances from
anywhere in the world even we are sitting a cup of tea in United States of America. Secondly,
it reduces wastage of electricity as discussed earlier that if we forget to switch off the lights.
Last but not the least it is very low cost compared to other technologies like GSM.
III. Introduction to Project – DTMF based Home Appliance
System
Traditionally electrical appliances in a home are controlled via switches that regulate the
electricity to these devices. As the world gets more and more technologically advanced, we
find new technology coming in deeper and deeper into our personal lives even at home.
Home automation is becoming more and more popular around the world and is becoming a
common practice. The process of home automation works by making everything in the house
automatically controlled using technology to control and do the jobs that we would normally
do manually. Home automation takes care of a lot of different activities in the house.
In the above project we can control any electrical appliances through mobile or landline from
any part of the country. One base unit is connected to the basic mobile phone in parallel with
the other mobile phone. When we want to control any electrical appliances through outer
phone then first we dial the home number, bell is ringing and after few seconds bell phone is
automatic on and that switches on the base unit to operate. Now we press the single digital
excess code, if the excess code is ok then unit give a tone pulse and switch on the base unit.
Now, again we press the switch on/off code to on/off any electrical appliances. With the help
of this code unit is on and base unit give a acknowledge pulse for on and off separately.

We are going to develop a cellular phone based home/office appliance. This system is
designed for controlling arbitrary devices, it includes a cell phone (not included with the
system kit, end user has to connect his/her cell phone to the system) which is connect to the
system via head set. To active the cellular phone unit on the system a call is to be made and
as the call is answered, in response the user would enter a two/three digit password to access
the system to control devices. As the caller press the specific password, it results in turning
ON or OFF specific device. The device switching is achieved by Relays. Security preserved
because these dedicated passwords owned and known by selected persons only. For instance,
our system contains an alarm unit giving the user a remote on/off mechanism, which is
capable of informing up to five different numbers over telephony network about the nature of
the event.
This project we propose a unique System for Home automation utilizing Dual Tone Multi
Frequency (DTMF) that is paired with a wireless module to provide seamless wireless control
over many devices in a house. The block diagram is a shown below. This user console has
many keys, each corresponding to the device that needs to be activated. The encoder encodes
the user choice and sends via a FM transmitter. The FM receiver receives the modulated
signal and demodulates it and the user choice is determined by the DTMF decoder. Based
upon this the required appliance is triggered.
Complete circuit is divided into four parts.
1. DTMF DECODER
2. MICROCONTROLLER
3. EXCESS CONTROL CIRCUIT
4. AUTOMATIC ON THROUGH OUTER PHONE
III.1 DTMF Signalling
Dual-tone multi-frequency signaling (DTMF) is used for telecommunication signaling over
analog telephone lines in the voice-frequency band between telephone handsets and other
communications devices and the switching center. The version of DTMF that is used in push-
button telephones for tone dialing is known as Touch-Tone. It was developed by Western
Electric and first used by the Bell System in commerce, using that name as a registered
trademark. DTMF is standardized by ITU-T Recommendation Q.23. It is also known in the
UK as MF4.
Other multi-frequency systems are used for internal signaling within the telephone network.
Introduced by AT&T in 1963, the Touch-Tone system using the telephone keypad gradually
replaced the use of rotary dial and has become the industry standard for landline service.

Prior to the development of DTMF, numbers were dialled on automated telephone systems by
means of pulse dialing (dial pulse, DP, in the U.S.) or loop disconnect (LD) signalling, which
functions by rapidly disconnecting and re-connecting the calling party's telephone line,
similar to flicking a light switch on and off. The repeated interruptions of the line, as
the dial spins, sounds like a series of clicks. The exchange equipment interprets these dial
pulses to determine the dialed number. Loop disconnect range was restricted by telegraphic
distortion and other technical problems, and placing calls over longer distances required
either operator assistance (operators used an earlier kind of multi-frequency dial) or the
provision of subscriber trunk dialing equipment.
Other vendors of compatible telephone equipment called the Touch-Tone feature Tone
dialing or DTMF, or used their own registered trade names such as the Digitone of Northern
Electric (later known as Nortel Networks).
The DTMF system uses eight different frequency signals transmitted in pairs to represent 16
different numbers, symbols and letters - as detailed below.
As a method of in-band signaling, DTMF tones were also used by cable
television broadcasters to indicate the start and stop times of local commercial insertion
points during station breaks for the benefit of cable companies. Until better out-of-band
signaling equipment was developed in the 1990s, fast, unacknowledged, and loud DTMF
tone sequences could be heard during the commercial breaks of cable channels in the United
States and elsewhere. Previously, terrestrial television stations also used DTMF tones to shut
off and turn on remote transmitters.
Multi-frequency signaling is a group of signaling methods that use a mixture of two pure
tone (pure sine wave) sounds. Various MF signaling protocols were devised by the Bell
System and CCITT. The earliest of these were for in-band signaling between switching
centers, where long-distance telephone operators used a 16-digitkeypad to input the next
portion of the destination telephone number in order to contact the next downstream long-
distance telephone operator. This semi-automated signaling and switching proved successful
in both speed and cost effectiveness. Based on this prior success with using MF by specialists
to establish long-distance telephone calls, Dual-tone multi-frequency (DTMF) signaling was
developed for the consumer to signal their own telephone-call's destination telephone number
instead of talking to a telephone operator.
AT&Ts Compatibility Bulletin No. 105 described the product as "a method for pushbutton
signaling from customer stations using the voice transmission path." In order to prevent
consumer telephones from interfering with the MF-based routing and switching between
telephone switching centers, DTMF's frequencies differ from all of the pre-existing MF
signaling protocols between switching centers: MF/R1, R2, CCS4, CCS5, and others that
were later replaced by SS7 digital signaling. DTMF, as used in push-button telephone tone
dialing, was known throughout the Bell System by the trademark Touch-Tone. This term was
first used by AT&T in commerce on July 5, 1960 and then was introduced to the public on
November 18, 1963, when the first push-button telephone was made available to the public. It
was AT&T's registered trademark from September 4, 1962 to March 13, 1984, and is
standardized by ITU-T Recommendation Q.23. It is also known in the UK as MF4.
The engineers had envisioned phones being used to access computers, and surveyed a number
of companies to see what they would need for this role. This led to the addition of the number

sign (#, ''pound'' or "diamond" in this context, "hash", "square" or "gate" in the UK, and
"octothorpe'' by the original engineers) and asterisk or "star" (*) keys as well as a group of
keys for menu selection: A, B, C and D. In the end, the lettered keys were dropped from most
phones, and it was many years before the two symbol keys became widely used for vertical
service codes such as *67 in the United States of America and Canada to suppress caller ID.
Public payphones that accept credit cards use these additional codes to send the information
from the magnetic strip.
The United States Armed Forces also used the letters, relabelled, in their now-
defunct AUTOVON telephone system to indicate the priority of a call. Precedence dialing is
still done on the military phone networks, but using number combinations (Example:
Entering 93 before a number is a priority call) rather than the separate tones and
the Government Emergency Telecommunications Service has superseded AUTOVON for
any civilian priority telephone company access.
Present-day uses of the A, B, C and D keys on telephone networks are few, and exclusive to
network control. For example, the A key is used on some networks to cycle through different
carriers at will (thereby listening in on calls). Their use is probably prohibited by most
carriers. The A, B, C and D tones are used in radio phone patch and repeater operations to
allow, among other uses, control of the repeater while connected to an active phone line.
The *, #, A, B, C and D keys are still widely used worldwide by amateur radio operators for
repeater control, remote-base operations and some telephone communications systems.
DTMF signaling tones can also be heard at the start or end of some VHS (Video Home
System) cassette tapes. Information on the master version of the video tape is encoded in the
DTMF tone. The encoded tone provides information to automatic duplication machines, such
as format, duration and volume levels, in order to replicate the original video as closely as
possible.
DTMF tones are sometimes used in caller ID systems to transfer the caller ID information,
but in the United States only Bell 202 modulated FSK signaling is used to transfer the data.
Fig 1. DTMF keypad layout.
Ac register signalling is used in dtmf telephones, here tones rather than make/break pulse are
used for dialling, and each dialled digit is uniquely represented by a pair of sine waves tones.
These tones (one from low group for row and another from high group from column) are sent
to the exchange when a digit is dialled by pushing the key, these tone lies within the speech
band of 300 to 3400 Hz, and are chosen so as to minimize the possibility of any valid
frequency pair existing in normal speech simultaneously. Actually, this minimisator is made
possible by forming pairs with one tone from the higher group and the other from the lower

of frequencies. A valid dtmf signal is the sum of two tones, one from a lower group (697-940
Hz) and the other from a higher group (1209-1663 Hz). Each group contains four individual
tones. This scheme allows 10 unique combinations. Ten of these code represent digits 1
through 9 and 0. Tones in DTMF dialling are so chose that none of the tones is harmonic of
are other tone. Therefore, there is no change of distortion caused by harmonics. Each tone is
sent as along as the key remains pressed. The dtmf signal contains only one component from
each of the high and low group. This significantly simplifies decoding because the composite
dtmf signal may be separated with band pass filters into single frequency components, each
of which may be handled individually.
Fig 2. 1209 Hz on 697 Hz to make the 1 tone
The underlying principle mainly relies up on the ability of DTMF (Double Tune Multi
Frequency) ICs to generate DTMF corresponding to a number or code in the number pad and
to detect the same number or code from its corresponding DTMF. In detail, a DTMF
generator generates two frequencies corresponding to a number or code in the number pad
which will be transmitted through the communication networks, constituting the transmitter
section which is simply equivalent to a mobile set. In the receiver part, the DTMF detector
IC, for example IC MT 8870 detects the number or code represented by DTMF back, through
the inspection of the two transmitted frequencies. The DTMF frequencies representing the
number/ codes are shown below.
Table 1. DTMF keypad frequencies (with sound clips)

IV. Modular Description
List of components used in the project are:-
1. Microcontroller - AT89S52
2. DTMF Decoder – MT8870
3. ULN 2003
4. Relay
5. Led
6. Resistors
7. Pull – Up Resistor
8. Capacitors
9. Crystal Oscillator
10. Push Button
11. Mic
12. Voltage Regulator
13. Bulb Holders
14. Bulbs
15. Plug
16. AC Power Supply
1. Microcontroller - AT89S52
Fig 3. Architecture of 8051 Family

1.1 Features
• Compatible with MCS-51™ Products
• 4K Bytes of In-System Reprogrammable Flash Memory
– Endurance: 1,000 Write/Erase Cycles
• Fully Static Operation: 0 Hz to 24 MHz
• Three-Level Program Memory Lock
• 128 x 8-Bit Internal RAM
• 32 Programmable I/O Lines
• Two 16-Bit Timer/Counters
• Six Interrupt Sources
• Programmable Serial Channel
• Low Power Idle and Power Down Modes
1.2 Description
The AT89S51 is a low-power, high-performance CMOS 8-bit microcomputer with 4K bytes
of Flash Programmable and Erasable Read Only Memory (PEROM). The device is
manufactured using Atmel’s high density nonvolatile memory technology and is compatible
with the industry standard MCS-51™ instruction set and pinout. The on-chip Flash allows the
program memory to be reprogrammed in-system or by a conventional nonvolatile memory
programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel
AT89S51 is a powerful microcomputer which provides a highly flexible and cost effective
solution to many embedded control applications. The AT89S51 provides the following
standard features: 4K bytes of Flash, 128 bytes of RAM, 32 I/O lines, two 16-bit timer/counters,
five vector two-level interrupt architecture, a full duplex serial port, and on-chip oscillator and
clock circuitry.
In addition, the AT89S51 is designed with static logic for operation down to zero frequency
and supports two software selectable power saving modes. The Idle Mode stops the CPU while
allowing the RAM, timer/counters, serial port and interrupt system to continue functioning.

The Power down Mode saves the RAM contents but freezes the oscillator disabling all other
chip functions until the next hardware reset.
1.3 Pin Description
Fig 4. Pin diagram of 8051

VCC
Supply voltage.
GND
Ground.
Port 0
Port 0 is an 8-bit open drain bidirectional I/O port. As an output port each pin can sink eight
TTL inputs. When 1s are written to port 0 pins, the pins can be used as high impedance inputs.
Port 0 may also be configured to be the multiplexed low order address/data bus during accesses
to external program and data memory. In this mode P0 has internal pull-ups. Port 0 also receives
the code bytes during Flash programming, and outputs the code bytes during program
verification.
External pull-ups are required during program verification.
Port 1
Port 1 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 1 output buffers can
sink/source four TTL inputs. When 1s are written to Port 1 pins they are pulled high by the
internal pull-ups and can be used as inputs. As inputs, Port 1 pins that are externally being
pulled low will source current (IIL) because of the internal pull-ups. Port 1 also receives the
low-order address bytes during Flash programming and verification.
Port 2
pulled low will source current (IIL) because of the internal pull-ups. Port 2 emits the high-order
address byte during fetches from external program memory and during accesses to external
data memory that uses 16-bit addresses (MOVX @ DPTR). In this application it uses strong
internal pull-ups when emitting 1s. During accesses to external data memory that uses 8-bit
addresses (MOVX @ RI); Port 2 emits the contents of the P2 Special Function Register. Port

2 also receives the high-order address bits and some control signals during Flash programming
and verification.
Port 3
pulled low will source current (IIL) because of the pull-ups. Port 3 also serves the functions of
various special features of the AT89S51 as listed below:
Port 3 also receives some control signals for Flash programming and verification.
RST
Reset input. A high on this pin for two machine cycles while the oscillator is running resets the
device.
ALE/PROG
Address Latch Enable output pulse for latching the low byte of the address during accesses to
external memory. This pin is also the program pulse input (PROG) during Flash programming.
In normal operation ALE is emitted at a constant rate of 1/6 the oscillator frequency, and may
be used for external timing or clocking purposes. Note, however, that one ALE pulse is skipped
during each access to external Data Memory. If desired, ALE operation can be disabled by
setting bit 0 of SFR location 8EH. With the bit set, ALE is active only during a MOVX or
MOVC instruction. Otherwise, the pin is weakly pulled high. Setting the ALE-disable bit has
no effect if the microcontroller is in external execution mode.
PSEN
Program Store Enable is the read strobe to external program memory.

Port Pin Alternate Functions
P3.0 RXD (serial input port)
P3.1 TXD (serial output port)
P3.2 INT0 (external interrupt 0)
P3.3 INT1 (external interrupt 1)
P3.4 T0 (timer 0 external input)
P3.5 T1 (timer 1 external input)
P3.6 WR (external data memory write strobe)
P3.7 RD (external data memory read strobe)
When the AT89S51 is executing code from external program memory, PSEN is activated twice
each machine cycle, except that two PSEN activations are skipped during each access to
external data memory.
EA/VPP
External Access Enable. EA must be strapped to GND in order to enable the device to fetch
code from external program memory locations starting at 0000H up to FFFFH. Note, however,
that if lock bit 1 is programmed, EA will be internally latched on reset. EA should be strapped
to VCC for internal program executions. This pin also receives the 12-volt programming enable
voltage (VPP) during Flash programming, for parts that require 12-volt VPP.
XTAL1
Input to the inverting oscillator amplifier and input to the internal clock operating circuit.
XTAL2
Output from the inverting oscillator amplifier.

Oscillator Characteristics
XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier which can
be configured for use as an on-chip oscillator, as shown in Figure 1. Either a quartz crystal or
ceramic resonator may be used. To drive the device from an external clock source, XTAL2
should be left unconnected while XTAL1 is driven as shown in Figure 2.There are no
requirements on the duty cycle of the external clock signal, since the input to the internal
clocking circuitry is through a divide-by-two flip-flop, but minimum and maximum voltage
high and low time specifications must be observed.
Fig 5. External Clock Drive Configuration
Idle Mode
In idle mode, the CPU puts itself to sleep while all the on chip peripherals remain active. The
mode is invoked by software. The content of the on-chip RAM and all the special functions
registers remain unchanged during this mode. The idle mode can be terminated by any enabled
Interrupt or by hardware reset. It should be noted that when idle is terminated by a Hardware
reset, the device normally resumes program execution, from where it left off, up to two machine

cycles before the internal reset algorithm takes control. On-chip hardware inhibits access to
internal RAM in this event, but access to the port pins is not inhibited. To eliminate the
possibility of an unexpected write to a port pin when Idle is terminated by reset, the instruction
following the one that invokes Idle should not be one that writes to a port pin or to external
memory.
Status of External Pins during Idle and Power down Modes
Mode Program Memory ALE PSEN PORT0 PORT1 PORT2 PORT3
Idle Internal 1 Data
Idle External 1 Float Data Address Data
Power down Internal 0 Data
Power down External 0 Float Data
Power down Mode
In the power down mode the oscillator is stopped, and the instruction that invokes power down
is the last instruction executed. The on-chip RAM and Special Function Registers retain their
values until the power down mode is terminated. The only exit from power down is a hardware
reset. Reset redefines the SFRs but does not change the on-chip RAM. The reset should not be
activated before VCC is restored to its normal operating level and must be held active long
enough to allow the oscillator to restart and stabilize.
Program Memory Lock Bits
On the chip are three lock bits which can be left un-programmed (U) or can be programmed
(P) to obtain the additional features listed in the table below:
When lock bit 1 is programmed, the logic level at the EA pin is sampled and latched during
reset. If the device is powered up without a reset, the latch initializes to a random value, and
holds that value until reset is activated. It is necessary that the latched value of EA be in
agreement with the current logic level at that pin in order for the device to function properly.

Lock Bit Protection Modes
Program Lock Bits Protection Type
LB1 LB2 LB3
1 U No program lock features.
2 P U MOVC instructions executed from external program memory are disabled from fetching
code
Bytes from internal memory, EA is sampled and latched on reset, and further programming of
the
Flash is disabled.
3 P U Same as mode 2, also verify is disabled.
4 P same as mode 3, also external execution is disabled.
Programming the Flash
The AT89S51 is normally shipped with the on-chip Flash memory array in the erased state
(that is, contents = FFH) and ready to be programmed. The programming interface accepts
either a high-voltage (12-volt) or a low-voltage (VCC) program enable signal. The low voltage
programming mode provides a convenient way to program the AT89S51 inside the user’s
system, while the high-voltage programming mode is compatible with conventional third party
Flash or EPROM programmers. The AT89S51 is shipped with either the high-voltage or low-
voltage programming mode enabled. The respective top-side marking and device signature
codes are listed in the following table. The AT89S51 code memory array is programmed byte-
by byte
In either programming mode. To program any nonblank byte in the on-chip Flash Memory, the
entire memory must be erased using the Chip Erase Mode.
Programming Algorithm:

Before programming the AT89S51, the address, data and control signals should be set up
according to the Flash programming mode table and Figures 3 and 4. To program the AT89S51,
take the following steps.
1. Input the desired memory location on the address lines.
2. Input the appropriate data byte on the data lines.
3. Activate the correct combination of control signals.
4. Raise EA/VPP to 12V for the high-voltage programming mode.
5. Pulse ALE/PROG once to program a byte in the Flash array or the lock bits. The byte-write
cycle is self-timed and typically takes no more than 1.5 ms. Repeat steps 1 through 5, changing
the address and data for the entire array or until the end of the object file is reached.
Data Polling:
The AT89S51 features Data Polling to indicate the end of a write cycle. During a write cycle,
an attempted read of the last byte written will result in the complement of the written datum on
PO.7. Once the write cycle has been completed, true data are valid on all outputs, and the next
cycle may begin. Data Polling may begin any time after a write cycle has been initiated.
Ready/Busy:
The progress of byte programming can also be monitored by the RDY/BSY output signal. P3.4
is pulled low after ALE goes high during programming to indicate BUSY. P3.4 is pulled high
again when programming is done to indicate READY.
Program Verify:
If lock bits LB1 and LB2 have not been programmed, the programmed code data can be read
back via the address and data lines for verification. The lock bits cannot be verified directly.
Verification of the lock bits is achieved by observing that their features are enabled.

Chip Erase:
The entire Flash array is erased electrically by using the proper combination of control signals
and by holding ALE/PROG low for 10 ms. The code array is written with all “1”s. The chip
erase operation must be executed before the code memory can be re-programmed.
Reading the Signature Bytes:
The signature bytes are read by the same procedure as a normal verification of locations 030H,
031H, and 032H, except that P3.6 and P3.7 must be pulled to a logic low. The values returned
are as follows.
(030H) = 1EH indicates manufactured by Atmel
(031H) = 51H indicates 89S51
(032H) = FFH indicates 12V programming
(032H) = 05H indicates 5V programming
Programming Interface
Every code byte in the Flash array can be written and the entire array can be erased by using
the appropriate combination of control signals. The write operation cycle is self timed and once
initiated, will automatically time itself to completion. All major programming vendors offer
worldwide support for the Atmel microcontroller series. Please contact your local
programming vendor for the appropriate software revision.
Flash Programming Modes
Note: 1. Chip Erase requires a 10-ms PROG pulse.
SPECIAL FUNCTION REGISTER (SFR) ADDRESSES:
ACC ACCUMULATOR 0E0H

B B REGISTER 0F0H
PSW PROGRAM STATUS WORD 0D0H
SP STACK POINTER 81H
DPTR DATA POINTER 2 BYTES
DPL LOW BYTE OF DPTR 82H
DPH HIGH BYTE OF DPTR 83H
P0 PORT0 80H
P1 PORT1 90H
P2 PORT2 0A0H
P3 PORT3 0B0H
TMOD TIMER/COUNTER MODE CONTROL 89H
TCON TIMER COUNTER CONTROL 88H
TH0 TIMER 0 HIGH BYTE 8CH
TLO TIMER 0 LOW BYTE 8AH
TH1 TIMER 1 HIGH BYTE 8DH
TL1 TIMER 1 LOW BYTE 8BH
SCON SERIAL CONTROL 98H
SBUF SERIAL DATA BUFFER 99H
PCON POWER CONTROL 87H
TMOD (TIMER MODE) REGISTER

Both timers are the 89S51 share the one register TMOD. 4 LSB bit for the timer 0 and 4 MSB
for the timer 1.
In each case lower 2 bits set the mode of the timer
Upper two bits set the operations.
GATE: Gating control when set. Timer/counter is enabled only while the INTX pin is high and
the TRx control pin is set. When cleared, the timer is enabled whenever the TRx control bit is
set.
C/T: Timer or counter selected cleared for timer operation (input from internal system clock)
M1 Mode bit 1
M0 Mode bit 0
M1 M0 MODE OPERATING MODE
0 0 0 13 BIT TIMER/MODE
0 1 1 16 BIT TIMER MODE
1 0 2 8 BIT AUTO RELOAD
1 1 3 SPLIT TIMER MODE
PSW (PROGRAM STATUS WORD)
CY PSW.7 CARRY FLAG
AC PSW.6 AUXILIARY CARRY
F0 PSW.5 AVAILABLE FOR THE USER FRO GENERAL PURPOSE
RS1 PSW.4 REGISTER BANK SELECTOR BIT 1

RS0 PSW.3 REGISTER BANK SELECTOR BIT 0
0V PSW.2 OVERFLOW FLAG
-- PSW.1 USER DEFINABLE BIT
P PSW.0 PARITY FLAG SET/CLEARED BY HARDWARE
PCON REGISATER (NON BIT ADDRESSABLE)
If the SMOD = 0 (DEFAULT ON RESET)
TH1 = CRYSTAL FREQUENCY
256---- ____________________
384 X BAUD RATE
If the SMOD IS = 1
CRYSTAL FREQUENCY
TH1 = 256--------------------------------------
192 X BAUD RATE
There are two ways to increase the baud rate of data transfer in the 8051
1. To use a higher frequency crystal
2. To change a bit in the PCON register
PCON register is an 8 bit register. Of the 8 bits, some are unused, and some are used for the
power control capability of the 8051. The bit which is used for the serial communication is D7,
the SMOD bit. When the 8051 is powered up, D7 (SMOD BIT) OF PCON register is zero. We
can set it to high by software and thereby double the baud rate

BAUD RATE COMPARISION FOR SMOD = 0 AND SMOD =1
TH1 (DECIMAL) HEX SMOD =0 SMOD =1
-3 FD 9600 19200
-6 FA 4800 9600
-12 F4 2400 4800
-24 E8 1200 2400
XTAL = 11.0592 MHZ
IE (INTERRUPT ENABLE REGISTOR)
EA IE.7 Disable all interrupts if EA = 0, no interrupts is acknowledged
If EA is 1, each interrupt source is individually enabled or disabled
By sending or clearing its enable bit.
IE.6 NOT implemented
ET2 IE.5 enables or disables timer 2 overflag in 89c52 only
ES IE.4 Enables or disables all serial interrupt
ET1 IE.3 Enables or Disables timer 1 overflow interrupt
EX1 IE.2 Enables or disables external interrupt
ET0 IE.1 Enables or Disables timer 0 interrupt.
EX0 IE.0 Enables or Disables external interrupt 0
INTERRUPT PRIORITY REGISTER
If the bit is 0, the corresponding interrupt has a lower priority and if the bit is 1 the
corresponding interrupt has a higher priority

IP.7 NOT IMPLEMENTED, RESERVED FOR FUTURE USE.
IP.6 NOT IMPLEMENTED, RESERVED FOR FUTURE USE
PT2 IP.5 DEFINE THE TIMER 2 INTERRUPT PRIORITY LELVEL
PS IP.4 DEFINES THE SERIAL PORT INTERRUPT PRIORITY LEVEL
PT1 IP.3 DEFINES THE TIMER 1 INTERRUPT PRIORITY LEVEL
PX1 IP.2 DEFINES EXTERNAL INTERRUPT 1 PRIORITY LEVEL
PT0 IP.1 DEFINES THE TIMER 0 INTERRUPT PRIORITY LEVEL
PX0 IP.0 DEFINES THE EXTERNAL INTERRUPT 0 PRIORITY LEVEL
SCON: SERIAL PORT CONTROL REGISTER, BIT ADDRESSABLE
SCON
SM0 : SCON.7 Serial Port mode specified
SM1 : SCON.6 Serial Port mode specifier
SM2 : SCON.5
REN : SCON.4 Set/cleared by the software to Enable/disable reception
TB8 : SCON.3 the 9th
bit that will be transmitted in modes 2 and 3, Set/cleared
By software
RB8 : SCON.2 In modes 2 &3, is the 9th
data bit that was received. In mode 1,
If SM2 = 0, RB8 is the stop bit that was received. In mode 0
RB8 is not used
T1 : SCON.1 Transmit interrupt flag. Set by hardware at the end of the 8th
bit
R1 SCON.0 Receive interrupt flag. Set by hardware at the end of the 8th
bit

TCON TIMER COUNTER CONTROL REGISTER
This is a bit addressable
TF1 TCON.7 Timer 1 overflows flag. Set by hardware when the Timer/Counter 1
Overflows. Cleared by hardware as processor
TR1 TCON.6 Timer 1 run control bit. Set/cleared by software to turn Timer
Counter 1 On/off
TF0 TCON.5 Timer 0 overflows flag. Set by hardware when the timer/counter 0
Overflows. Cleared by hardware as processor
TR0 TCON.4 Timer 0 run control bit. Set/cleared by software to turn timer
Counter 0 on/off.
IE1 TCON.3 External interrupt 1 edge flag
ITI TCON.2 Interrupt 1 type control bit
IE0 TCON.1 External interrupt 0 edge
IT0 TCON.0 Interrupt 0 type control bit.
MCS-51 FAMILY INSTRUCTION SET
Notes on Data Addressing Modes
Rn - Working register R0-R7
Direct - 128 internal RAM locations, any l/O port, control or status register
@Ri - Indirect internal or external RAM location addressed by register R0 or R1
#data - 8-bit constant included in instruction
#data 16 - 16-bit constant included as bytes 2 and 3 of instruction
Bit - 128 software flags, any bit addressable l/O pin, control or status bit

A - Accumulator
Notes on Program Addressing Modes
addr16 - Destination address for LCALL and LJMP may be anywhere within the 64-Kbyte
program memory address space. addr11 - Destination address for ACALL and AJMP will be
within the same 2-Kbyte page of program memory as the first byte of the following instruction.
Rel - SJMP and all conditional jumps include an 8 bit offset byte. Range is + 127/– 128 bytes
relative to the first byte of the following instruction.
ACALL addr11
Function: Absolute call
Description: ACALL unconditionally calls a subroutine located at the indicated address. The
instruction increments the PC twice to obtain the address of the following instruction, then
pushes the 16-bit result onto the stack (low-order byte first) and increments the stack pointer
twice. The destination address is obtained by successively concatenating the five high-order
bits of the incremented PC, op code bits 7-5, and the second byte of the instruction. The
subroutine called must therefore start within the same 2K block of program memory as the first
byte of the instruction following ACALL. No flags are affected. Example: Initially SP equals
07H. The label”SUBRTN” is at program memory location 0345H. After executing the
instruction ACALL SUBRTN at location 0123H, SP will contain 09H, internal RAM location
08H and 09H will contain 25H and 01H, respectively, and the PC will contain 0345H.
Operation: ACALL
(PC) ¬ (PC) + 2
(SP) ¬ (SP) + 1
((SP)) ¬ (PC7-0)
(SP) ¬ (SP) + 1
((SP)) ¬ (PC15-8)

(PC10-0) ¬ Page address
Bytes: 2
Cycles: 2
Encoding: a10 a9 a8 1 0 0 0 1 a7 a6 a5 a4 a3 a2 a1 a0
JB bit, rel
Function: Jump if bit is set
Description: If the indicated bit is a one, jump to the address indicated; otherwise proceed with
the next instruction. The branch destination is computed by adding the signed relative-
displacement in the third instruction byte to the PC, after incrementing the PC to the first byte
of the next instruction. The bit tested is not modified. No flags are affected.
Example: The data present at input port 1 is 11001010B. The accumulator holds 56
(01010110B). The instruction sequence
JB P1.2, LABEL1
JB ACC.2, LABEL2
will cause program execution to branch to the instruction at label LABEL2.
Operation: JB
(PC) ¬ (PC) + 3
if (bit) = 1
then (PC) ¬ (PC) + rel
Bytes: 3
Cycles: 2
Encoding: 0 0 1 0 0 0 0 0 bit address rel. address
JNB bit, rel
Function: Jump if bit is not set

Description: If the indicated bit is a zero, branch to the indicated address; otherwise proceed
with the next instruction. The branch destination is computed by adding the signed relative-
displacement in the third instruction byte to the PC, after incrementing the
PC to the first byte of the next instruction. The bit tested is not modified. No flags are affected.
Example: The data present at input port 1 is 11001010B. The accumulator holds 56H
(01010110B). The instruction sequence
JNB P1.3, LABEL1
JNB ACC.3, LABEL2
will cause program execution to continue at the instruction at label LABEL2.
Operation: JNB
(PC) ¬ (PC) + 3
if (bit) = 0
then (PC) ¬ (PC) + rel.
Bytes: 3
Cycles: 2
Encoding: 0 0 1 1 0 0 0 0 bit address rel. address
LCALL addr16
Function: Long call
Description: LCALL calls a subroutine located at the indicated address. The instruction adds
three to the program counter to generate the address of the next instruction and then pushes the
16-bit result onto the stack (low byte first), incrementing the stack pointer by two. The high-
order and low-order bytes of the PC are then loaded, respectively, with the second and third
bytes of the LCALL instruction. Program execution continues with the instruction at this
address. The subroutine may therefore begin anywhere in the full 64 Kbytes program memory
address space. No flags are affected.

Example: Initially the stack pointer equals 07H. The label”SUBRTN” is assigned to program
memory location 1234H. After executing the instruction
LCALL SUBRTN
at location 0123H, the stack pointer will contain 09H, internal RAM locations 08H and 09H
will contain 26H and 01H, and the PC will contain 1234H.
Operation: LCALL
(PC) ¬ (PC) + 3
(SP) ¬ (SP) + 1
((SP)) ¬ (PC7-0)
(SP) ¬ (SP) + 1
((SP)) ¬ (PC15-8)
(PC) ¬ addr15-0
Bytes: 3
Cycles: 2
Encoding: 0 0 0 1 0 0 1 0 addr15. . addr8 addr7. . addr0
MOV <dest-byte>, <src-byte>
Function: Move byte variable
Description: The byte variable indicated by the second operand is copied into the location
specified by the first operand. The source byte is not affected. No other register or flag is
affected. This is by far the most flexible operation. Fifteen combinations of source and
destination addressing modes are allowed.
Example: Internal RAM location 30H holds 40H. The value of RAM location 40H is 10H. The
data present at input port 1 is 11001010B (0CAH).
MOV R0, #30H; R0 < = 30H

MOV A, @R0; A < = 40H
MOV R1, A; R1 < = 40H
MOV B, @R1; B < = 10H
MOV @R1, P1; RAM (40H) < = 0CAH
MOV P2, P1; P2 < = 0CAH
leaves the value 30H in register 0, 40H in both the accumulator and register 1, 10H
in register B, and 0CAH (11001010B) both in RAM location 40H and output on port 2.
MOV A, Rn
Operation: MOV
(A) ¬ (Rn)
Bytes: 1
Cycles: 1
RET
Function: Return from subroutine
Description: RET pops the high and low-order bytes of the PC successively from the stack,
decrementing the stack pointer by two. Program execution continues at the resulting address,
generally the instruction immediately following an ACALL or LCALL. No flags are affected.
Example: The stack pointer originally contains the value 0BH. Internal RAM locations 0AH
and 0BH contain the values 23H and 01H, respectively. The instruction RET will leave the
stack pointer equal to the value 09H. Program execution will continue at location 0123H.
Operation: RET

(PC15-8) ¬ ((SP))
(SP) ¬ (SP) – 1
(PC7-0) ¬ ((SP))
(SP) ¬ (SP) – 1
Bytes: 1
Cycles: 2
Encoding: 0 0 1 0 0 0 1 0
SETB <bit>
Function: Set bit
Description: SETB sets the indicated bit to one. SETB can operate on the carry flag or any
directly addressable bit. No other flags are affected.
Example: The carry flag is cleared. Output port 1 has been written with the value 34H
(00110100B). The instructions
SETB C
SETB P1.0
will leave the carry flag set to 1 and change the data output on port 1 to 35H (00110101B).
SETB C
Operation: SETB
(C) ¬ 1
Bytes: 1
Cycles: 1
SETB bit

Operation: SETB
(bit) ¬ 1
Bytes: 2
Cycles: 1
Encoding: 1 1 0 1 0 0 1 1
Encoding: 1 1 0 1 0 0 1 0 bit address
SJMP rel
Function: Short jump
Description: Program control branches unconditionally to the address indicated. The branch
destination is computed by adding the signed displacement in the second instruction byte to the
PC, after incrementing the PC twice. Therefore, the range of destinations allowed is from 128
bytes preceding this instruction to 127 bytes following it.
Example: The label ”RELADR” is assigned to an instruction at program memory location
0123H. The instruction
SJMP RELADR
will assemble into location 0100H. After the instruction is executed, the PC will contain the
value 0123H.
Note:
Under the above conditions the instruction following SJMP will be at 102H. Therefore, the
displacement byte of the instruction will be the relative offset (0123H-0102H) = 21H. In other
words, an SJMP with a displacement of 0FEH would be a one-instruction infinite loop.
Operation: SJMP
(PC) ¬ (PC) + 2
(PC) ¬ (PC) + rel
Bytes: 2

Cycles: 2
Encoding: 1 0 0 0 0 0 0 0 rel. address
Fig 5. ATMEL SERIES OF MICROCONTROLLERS
2. DTMF Decoder – MT8870
In DTMF decoder circuit we use IC MT8870. It converts the dual tones to corresponding
binary outputs.
F low F high KEY BCD
697 1209 1 0001
697 1336 2 0010
697 1477 3 0011
770 1209 4 0100
770 1336 5 0101

770 1477 6 0110
852 1209 7 0111
852 1336 8 1000
852 1477 9 1001
941 1209 0 1010
Table 2. MT8870 OUTPUT TRUTH TABLE
3. ULN 2003
A ULN2003 is a high-voltage, high-current Darlington transistor array.
It consists of seven NPN Darlington pairs that feature high-voltage outputs with common-
cathode flyback diodes for switching inductive loads.
It is very similar to the ULN2801A, ULN2802A, ULN2803A, ULN2804A, and ULN2805A,
only differing in logic input levels (TTL,CMOS, PMOS) and number of inputs (8).
The drivers can be paralleled for higher current capability, even stacking one chip on top of
another, both electrically and physically has been done.
Fig 7. Pin diagram of ULN 2003

3.1 Features
 500 mA rated collector current (single output)
 50 V output
 Includes output flyback diodes
 Inputs compatible with various types of logic
3.2 Applications
Typical usage of the ULN2003A is to drive relays, lamp and LED displays or stepper motors.
4. Relay
A relay is an electrically operated switch. Many relays use an electromagnet to mechanically
operate a switch, but other operating principles are also used, such as solid-state relays.
Relays are used where it is necessary to control a circuit by a low-power signal (with
complete electrical isolation between control and controlled circuits), or where several
circuits must be controlled by one signal. The first relays were used in long
distance telegraph circuits as amplifiers: they repeated the signal coming in from one circuit
and re-transmitted it on another circuit. Relays were used extensively in telephone exchanges
and early computers to perform logical operations.
A type of relay that can handle the high power required to directly control an electric motor
or other loads is called a contactor. Solid-state relays control power circuits with no moving
parts, instead using a semiconductor device to perform switching. Relays with calibrated
operating characteristics and sometimes multiple operating coils are used to protect electrical
circuits from overload or faults; in modern electric power systems these functions are
performed by digital instruments still called "protective relays".
Fig 8. Simple electromechanical relay

5. Led
A light-emitting diode (LED) is a two-lead semiconductor light source. It is a basic pn-
junction diode, which emits light when activated. When a fitting voltage is applied to the
leads, electrons are able to recombine with electron holes within the device, releasing energy
in the form of photons. This effect is called electroluminescence, and the color of the light
(corresponding to the energy of the photon) is determined by the energy band gap of the
semiconductor.
Fig 9. Blue, pure green, and red LEDs in 5 mm diffused cases
Recent developments in LEDs permit them to be used in environmental and task lighting.
LEDs have many advantages over incandescent light sources including lower energy
consumption, longer lifetime, improved physical robustness, smaller size, and faster
switching. Light-emitting diodes are now used in applications as diverse as aviation
lighting, automotive headlamps, advertising, general lighting, traffic signals, and camera
flashes. However, LEDs powerful enough for room lighting are still relatively expensive, and
require more precise current and heat management than compact fluorescent lamp sources of
comparable output.
LEDs have allowed new text, video displays, and sensors to be developed, while their high
switching rates are also useful in advanced communications technology.
6. Capacitor
A capacitor (originally known as a condenser) is a passive two-terminal electrical
component used to store energy electrostatically in an electric field. The forms of practical
capacitors vary widely, but all contain at least two electrical conductors (plates) separated by
a dielectric (i.e. insulator). The conductors can be thin films of metal, aluminum foil or disks,
etc. The "nonconducting" dielectric acts to increase the capacitor's charge capacity. A
dielectric can be glass, ceramic, plastic film, air, paper, mica, etc. Capacitors are widely used
as parts of electrical circuits in many common electrical devices. Unlike aresistor, an ideal
capacitor does not dissipate energy. Instead, a capacitor stores energy in the form of
an electrostatic field between its plates.

Fig 10. A typical electrolytic capacitor
When there is a potential difference across the conductors (e.g., when a capacitor is attached
across a battery), an electric field develops across the dielectric, causing
positive charge +Q to collect on one plate and negative charge −Q to collect on the other
plate. If a battery has been attached to a capacitor for a sufficient amount of time, no current
can flow through the capacitor. However, if a time-varying voltage is applied across the leads
of the capacitor, a displacement current can flow.
Capacitors are widely used in electronic circuits for blocking direct current while
allowing alternating current to pass. In analog filternetworks, they smooth the output
of power supplies. In resonant circuits they tune radios to particular frequencies. In electric
power transmission systems, they stabilize voltage and power flow.
6.1. Capacitor filtering
The simple capacitor filter is the most basic type of power supply filter. The application of
the simple capacitor filter is very limited. It is sometimes used on extremely high-voltage,
low-current power supplies for cathode-ray and similar electron tubes, which require very
little load current from the supply. The capacitor filter is also used where the power-supply
ripple frequency is not critical; this frequency can be relatively high.
7. Resistor
A resistor is a passive two-terminal electrical component that implements electrical
resistance as a circuit element. Resistors act to reduce current flow, and, at the same time, act
to lower voltage levels within circuits. In electronic circuits resistors are used to limit current
flow, to adjust signal levels, bias active elements, terminate transmission lines among other
uses. High-power resistors that can dissipate many watts of electrical power as heat may be
used as part of motor controls, in power distribution systems, or as test loads for generators.
Fig 11. A typical axial-lead resistor

Resistors may have fixed resistances that only change a little with temperature, time or
operating voltage. Variable resistors can be used to adjust circuit elements (such as a volume
control or a lamp dimmer), or as sensing devices for heat, light, humidity, force, or chemical
activity.
8. Pull - Up Resistor
Pull-up resistors are used in electronic logic circuits to ensure that inputs to logic systems
settle at expected logic levels if external devices are disconnected or high-impedanceis
introduced. They may also be used at the interface between two different types of logic
devices, possibly operating at different power supply voltages.
Fig 12. When the switch is open the voltage of the gate input is pulled up to the level of Vin. When the switch is closed, the input voltage at
the gate goes to ground.
A pull-up resistor weakly "pulls" the voltage of the wire it is connected to towards its voltage
source level when the other components on the line are inactive. When all other connections
on the line are inactive, they are high-impedance and act like they are disconnected. Since the
other components act as though they are disconnected, the circuit acts as though it is
disconnected, and the pull-up resistor brings the wire up to the high logic level. When another
component on the line goes active, it will override the high logic level set by the pull-up
resistor. The pull-up resistor ensures that the wire is at a defined logic level even if no active
devices are connected to it.
9. Crystal Oscillator
A crystal oscillator is an electronic oscillator circuit that uses the mechanical resonance of a
vibrating crystal of piezoelectric material to create an electrical signal with a very
precise frequency.[1][2][3]
This frequency is commonly used to keep track of time (as in quartz
wristwatches), to provide a stable clock signal for digital integrated circuits, and to stabilize
frequencies for radio transmitters andreceivers. The most common type of piezoelectric
resonator used is the quartz crystal, so oscillator circuits incorporating them became known
as crystal oscillators,[1]
but other piezoelectric materials including polycrystalline ceramics
are used in similar circuits.

Fig 13. A miniature 16 MHz quartz crystal enclosed in a hermetically sealed HC-49/S package, used as the resonator in a crystal oscillator
Quartz crystals are manufactured for frequencies from a few tens of kilohertz to hundreds of
megahertz. More than two billion crystals are manufactured annually. Most are used for
consumer devices such as wristwatches, clocks, radios, computers, and cellphones. Quartz
crystals are also found inside test and measurement equipment, such as counters, signal
generators, and oscilloscopes.
10.AC Power Supply
Fig 14. Circuit diagram of Power Supply

V. Design
Fig 15. Block diagram of the circuit
Fig 16. Circuit diagram

V.1. Working
IN this project our first part is DTMF decoder. The DTMF IC receives the DTMF pulse and
then converts it into binary coded decimal. Pin No. 18 of the IC is connected to positive
supply. In this circuit we use +5 volt regulated power supply for the smooth working. DTMF
signal is applied to the pin No. 2 and 3 of the IC through resistor and capacitor network.
Capacitor of 0.1 uF works as a dc blocking capacitor. Pin No. 5, 6, 9 is connected to the
Ground pin. Pin No. 7 and 8 is connected to the 12.095 crystal. Pin No. 16 and 17 is
connected to RC network work as an auto reset, when we switch on the power supply.
BCD output is available on the pin No 11, 12, 13, 14 and this output is connected to the
microcontroller 89C51.
Our next part of the circuit is 89C51. 89C51 is a 40 pin IC. Pin No. 40 of the IC is connected
to the positive supply. Pin No. 9 is rest pin. One capacitor and resistor network is connected
to pin No 9. This microcontroller has a total of four input output ports each 8 bit wide.
We use port 2 as a BCD input. Output from the 8870 is connected to the p2 – 4 pins.
8870 PORT2 IC pin
Pin 11 p2.0 21
Pin 12 p2.1 22
Pin 13 p2.2 23
Pin 14 p2.3 24
Output is available on the port1 and port 3, here we use only 10 output from the
microcontroller. All the output is available on the PORT1.
P1.0 pin no 39
P1.1 pin no 38
P1.2 pin no 37
P1.3 pin no 36
P1.4 pin no 35
P1.5 pin no 34
P1.6 pin no 33
P1.7 pin no 32
P3.0 pin no 10
P3.1 pin no 11
All the output led is connected to this output. Note that 0 logic is available on these pin, so
cathode of the Led is connected to this pin.
Another pins of the port 3 is also connected for another useful uses.
P3.3 Acknowledge of code lock
P3.4 Time indication of the code lock
P3.5 Led indication of sound output for on/off signal
P3.2 Output frequency for opto-coupler input.

VI. Coding
VI.1. Software
The μ Vision IDE is, for most developers, the easiest way to create embedded system
programs. This chapter describes commonly used μ Vision features and explains how to use
them.

Keil software converts the C-codes into the Intel Hex code.

VI.2. Code
#include <REGX51.H>
sbit sw1=P1^0;
sbit sw2=P1^1;
sbit sw3=P1^2;
sbit sw4=P1^3;
sbit op1=P2^0;
sbit op2=P2^1;
sbit op3=P2^2;
sbit op4=P2^3;
sbit op5=P2^4;
sbit op6=P2^5;
sbit op7=P2^6;
void main()
{
if(sw1==1 && sw2==0 && sw3==0 && sw4==0)
{
op4=1;
}
else if(sw1==0 && sw2==1 && sw3==0 && sw4==0)
{
op5=1;
}
else if(sw1==1 && sw2==1 && sw3==0 && sw4==0)
{
op6=1;
}
else if(sw1==0 && sw2==0 && sw3==1 && sw4==0)
{
op7=1;
}
else if(sw1==1 && sw2==1 && sw3==0 && sw4==1)
{
P2=0xf8;
}
else if(sw1==0 && sw2==1 && sw3==0 && sw4==1)
{
P2=0x00;
}
else
{
P2 = 0x00;
}
}

VII. Test Cases
With the knowledge of operation of the system was tested step by step to the transistor output
and the load was connected across the collector terminal of the transistor.
VIII. Industry Applications
The need for the above project was that this project firstly it saves our time. If you are stuck
in traffic you can switch on your microwave oven on slow cooking mode. By the time you
reach your home your food will be ready. You don’t have go to each room to check whether
the lights are on/off. You can do with a click of single button. Secondly, it save our money in
the long run. There are some appliances like a television which we switch off but not its
power supply. There is a Led still glowing in it which uses electricity. If we have this
television attached to our project then we can switch off its power supply whenever we want
and there are many other devices like this. Thirdly, it for self-maintenance and security.
Security as in if we by chance forgot to switch off any of lights then we can switch off from
our phones. Lastly, we all know that all this will make our life easy and trouble free.
Industrial applications for the project made are that one can control home appliances from
anywhere in the world even we are sitting a cup of tea in United States of America. Secondly,
it reduces wastage of electricity as discussed earlier that if we forget to switch off the lights.
Last but not the least it is very low cost compared to other technologies like GSM.
IX. Future Enhancements
Future scope of the device can be that we instead of calling from one phone to other which
makes it costly we can send a message for the switching of lights. This will make it easier.

X. Data Sheets
X.1. AT89C51
Table 2. Flash Programming Modes

Table 3. Serial Programming Instruction Set

Fig 17. Block diagram of 8870
Table 4. Pin description of 8870

References
[1]. http://en.wikipedia.org/wiki/ULN2003A
[2]. http://en.wikipedia.org/wiki/Crystal_oscillator
[3]. http://en.wikipedia.org/wiki/Pull-up_resistor
[4]. http://en.wikipedia.org/wiki/Light-emitting_diode
[5]. http://en.wikipedia.org/wiki/Relay
[6]. http://en.wikipedia.org/wiki/Capacitor
[7]. http://en.wikipedia.org/wiki/Resistor
[8]. http://en.wikipedia.org/wiki/Dual-tone_multi-frequency_signaling
[9]. http://www.electronicshub.org/dtmf-controlled-home-automation-system-circuit/
[10]. http://www.engineersgarage.com/contribution/dtmf-controlled-home-automation-
system-using-8951?page=2

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