Remote controlled home appliance Project report

                                                                     ABSTRACT

The main aim of conducting this project is to control a maximum of eight electrical
appliances by just using a TV remote. Normal IR circuits can switch only one device. But
using this circuit, different devices can be controlled using same remote with different
switches. In this circuit, we interfaced 8 devices. These devices are switched using remote
keypad -1 to 8. AT89C2051 microcontroller is used to control the inputs and outputs. TSOP
1736 (infrared receiver) is used to receive the infrared signals from TV Remote. ULN2803
(High voltage, high current) buffer is used to drive relays. A working system will ultimately
be demonstrated to validate the design.
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                                                                         CHAPTER 1
                                                                     INTRODUCTION
Infrared (IR) light is an electromagnetic radiation with a wavelength longer than that
of visible light, measured from the nominal edge of visible red light at 0.7 micrometers, and
extending conventionally to 300 micrometers. These radiations with a frequency below our
eyes sensitivity cannot be seen, but can only be felt by our skin temperature sensors. Infra-
Red is interesting, because it is easily generated and doesn't suffer electromagnetic
interference and so it is widely used in communication and control circuits. The adventure of
using lots of infra-red in TV/VCR remote controls helped engineers to work on innovative
projects like controlling home appliances using TV remotes etc.
A TV remote that follows RC5 Protocol is used here. Receiver in the circuit receives
pulsed IR rays from the remote and sends them to a microcontroller that plays the role of a
decoder. Decoded signal is thus received by relay driver IC’s whose output activates the
corresponding home appliance. Thus this circuit can control the ON/OFF process of eight
appliances.
One of the major advantages of this circuit is to control any appliances by just being
in our living room. A major disadvantage is that obstacles on the path of IR rays can block its
remote sensing capabilities.
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CHAPTER 2
PROJECT ANALYSIS
2.1 Work Plan
Fig. 2.1. Block Diagram
2.1.1 Parts of the System
a. IR Transmitter
b. IR Receiver
c. Encoder
d. Decoder
e. Relays
f. Flip flops
g. Current Driver ICs
h. Home Appliances
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2.2 Methodology
As seen in the block diagram, our circuit consists of an IR transmitter, an IR receiver,
decoder, relay driver IC and relays. This is a simple type remote control by using RF
communication without microcontroller. In this project a remote has been designed for
various home appliances like television, fan, lights, etc. It gives lot of comfort to the user
since we can operate it by staying at one place. We can control any of the appliances by using
this remote within the range of 400 foots. In this project consist of two sections, transmitter
(remote) and receiver section. Whenever we are pressing any key in the remote it generates
the corresponding RF signals, and these signals are received by the receiver unit. ASK
transmitter and receiver is used as transmitter and receiver. HT12E, HT12D encoders and
decoders are used in this electronic circuit. The block digram of the whole circuit is given
below.
2.2.1 IR TRANSMITTER
The IR transmitter used in the circuit is a TV remote. As mentioned earlier a remote
that follows RC5 Protocol is being used in this circuit. A Phillip’s TV remote is a best
example for such remotes. As per this, IR signals from the remote are modulated by a carrier
frequency of 36 kHz. This is because there are many other IR sources like sun, light bulbs,
fire etc. In order to exclude other sources, IR signal is modulated.
2.2.2 IR RECEIVER
The IR receiver in the circuit is TSOP 1736. These are capable of receiving pulsed
IR rays of 36 kHz only and can receive no other frequencies. It receives the signals from the
transmitter and retrieves the original modulating signal from the 36 kHz carrier. The front
end of this module has a PIN photodiode and the input signal from the remote is passed into
an Automatic Gain Control (AGC) stage from which the signal passes into a Band pass filter
and finally into a demodulator. The demodulated output drives an NPN transistor. The
collector of this transistor forms the output of the module.
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2.2.3 IR DECODER
The microcontroller AT89C2051 is used as the IR decoder in the circuit. It is flashed
with a program that decodes the RC5 Protocol. It is designed to control the inputs and
outputs. The demodulated output from the receiver will be sensed and decoded using this
microcontroller. Thus it helps to determine which device is being operated by the user.
2.2.4 RELAY DRIVER IC
As we all know ULN2803 is used as the relay driver IC. It consists of octal high
voltage, high current Darlington transistor arrays. The eight NPN Darlington connected
transistors in this family of arrays are ideally suited for interfacing between low logic level
digital circuitry (such as TTL, CMOS or PMOS/NMOS) and the higher current/voltage
requirements of lamps, relays, printer hammers or other similar loads for a broad range of
computer, industrial, and consumer applications.
2.2.5 RELAYS
A relay is an electrically operated switch. It allows one circuit to switch a second
circuit which is completely separated from the first. The output from the driver IC is send to
the corresponding relays which thus results in its excitation and gets activated. As a result it
controls the corresponding home appliance.
2.2.6 Remote Section
In remote section consist of an encoder (HT 12E) and a ASK transmitter. The encoder
generates 8 bit address and 4bit data. We can set the address by using the DIP switch
connected in A0 to A7 (pin 1 to 8 ) encoder. If we set an address in the remote section, the
same address will be required in the receiver section. So always set same address in
transmitter and receiver. Whenever we press any key in the remote the encoder generates
corresponding 4bit data and send this data with 8bit address by using ASK transmitter. The
transmitting frequency is 433MHz. The transmitter output is up to 8mW at 433.92MHz.
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CHAPTER 3
PROJECT DESIGN
3.1 Circuit Diagram
Fig. 3.1. Circuit Diagram
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3.2 Component Used
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3.3 Working
Our project as mentioned earlier is aimed at controlling 8 home appliances using a
Philip’s TV remote or any remote supporting RC5 Protocol. It controls the on/off process of
the appliances interfaced to this circuit. The devices are operated using the keypads 1-8. It
performs the function of an IR transmitter which sends pulsed IR rays after modulating the
original signal with a carrier of 36 kHz frequency. These signals are received by TSOP 1736
which is our IR receiver. These are designed to receive signals of only 36 kHz. It senses the
received output and demodulates them. Therefore original signals are retrieved after
demodulation.
This is a simple type remote control by using RF communication without
microcontroller. In this project a remote has been designed for various home appliances like
television, fan, lights, etc. It gives lot of comfort to the user since we can operate it by staying
at one place. We can control any of the appliances by using this remote within the range of
400 foots. In this project consist of two sections, transmitter (remote) and receiver section.
Whenever we are pressing any key in the remote it generates the corresponding RF signals,
and these signals are received by the receiver unit. ASK transmitter and receiver is used as
transmitter and receiver. HT12E, HT12D encoders and decoders are used in this electronic
circuit. The block diagram of the whole circuit is given below.
In remote section consist of an encoder (HT 12E) and a ASK transmitter. The encoder
generates 8 bit address and 4bit data. We can set the address by using the DIP switch
connected in A0 to A7 (pin 1 to 8 ) encoder. If we set an address in the remote section, the
same address will be required in the receiver section. So always set same address in
transmitter and receiver. Whenever we press any key in the remote the encoder generates
corresponding 4bit data and send this data with 8bit address by using ASK transmitter. The
transmitting frequency is 433MHz. The transmitter output is up to 8mW at 433.92MHz with
a range of approximately 400 foot (open area) outdoors. Indoors, the range is approximately
200 foot.
At the receiver section ASK receiver is present. The receiver also operates at
433.92MHz, and has a sensitivity of 3uV. The ASK receiver operates from 4.5 to 5.5 volts9
DC, and has both linear and digital outputs. It receives the datas from the transmitter. Then
the decoder (HT 12D) decodes the date and it will enable the corresponding output pin (pin
10,11,12,13). Each output pins are connected to separate flip flops. The output of encoder
will change the state of the flip flop. So its output goes to set (high) from reset (low) state.
This change makes a high signal in the output of the flip flop. This output signal is not
capable to drive a relay directly. So we are using current driver, SL100 transistor act as the
current driver. The appliance is connected to 230V AC through the relay and the appliance
will start. The relay will be re-energized when the same switch is pressed in the remote. This
is because we are pressing the same switch in the remote control. The output of the decoder
again goes to high so this signal will again change the state of the flip flop. So, the relay gets
re-energized and the appliance goes to OFF state.
3.4 Circuit Description
3.4.1 RC5 Protocol
The RC-5 protocol was developed by Philips in the late 1980s as a semi proprietary
consumer IR (infrared) remote control communication protocol for consumer electronics.
However, it was also adopted by most European manufacturers, as well as many US
manufacturers of special audio and video equipment. The advantage of the RC-5 protocol is
that (when properly followed) any CD handset (for example) may be used to control any
brand of CD player using the RC-5 protocol.
Fig. 3.2. RC5 Protocol
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3.5 IR RECEIVER (TSOP1736)
The TSOP1736 are miniaturized receivers for infrared remote control
systems. PIN diode and preamplifier are assembled on lead frame, the epoxy
package is designed as IR filter. The demodulated output signal can directly be
decoded by a microprocessor. TSOP1736 is the standard IR remote control receiver series,
supporting all major transmission codes.
Fig. 3.3. TSOP 1736
The main features of these receivers are:
 Photo detector and preamplifier in one package
 Internal filter for PCM frequency
 Improved shielding against electrical field disturbance
 TTL and CMOS compatibility
 Output active low
 Low power consumption
 High immunity against ambient light
 Continuous data transmission possible(up to 2400 bps)
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The circuit of the TSOP1736 is designed in that way that unexpected output pulses due to
noise or disturbance signals are avoided. A band pass filter, an integrator stage and an
automatic gain control are used to suppress such disturbances.
The distinguishing mark between data signal and disturbance signal are carrier
frequency, burst length and duty cycle. The data signal should fulfill the following condition:
• Carrier frequency should be close to center frequency of the band pass (eg
36kHz).
• Burst length should be 10 cycles/burst or longer.
• After each burst which is between 10 cycles and 70cycles a gap time of at least
14 cycles is necessary.
• For each burst which is longer than 1.8ms a corresponding gap time is necessary
at some time in the data stream. This gap time should have at least same length as
the burst.
• Up to 1400 short bursts per second can be received continuously.
• Some examples for suitable data format are: NEC Code, Toshiba Micom
Format, Sharp Code, RC5Code, RC6 Code, R–2000 Code and Sony Format
(SIRCS).
• When a disturbance signal is applied to the TSOP1736 it can still receive the
data signal. However the sensitivity is reduced to that level that no unexpected
pulses will occur.
Some examples for such disturbance signals which are suppressed by the TSOP1736 are:
• DC light (e.g. from tungsten bulb or sunlight)
• Continuous signal at 36 kHz or at any other frequency.
• Signals from fluorescent lamps with electronic ballast.
3.6 RELAY DRIVER IC (ULN2803)
IC ULN2803 consists of octal high voltage, high current Darlington transistor arrays.
The eight NPN Darlington connected transistors in this family of arrays are ideally suited for
interfacing between low logic level digital circuitry (such as TTL, CMOS or PMOS/NMOS)
and the higher current/voltage requirements of lamps, relays, printer hammers or other similar
loads for a broad range of computer, industrial, and consumer applications. The main features
of ULN2803 are:
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Eight Darlington’s with Common Emitter.
Open–collector outputs.
Freewheeling clamp diodes for transient suppression.
Output Current to 500 mA.
Output Voltage to 50 V.
Inputs pinned opposite outputs to simplify board layout.
Fig 3.4. PIN DIAGRAM OF ULN2803
WORKING
The ULN 2803 IC consists of eight NPN Darlington connected transistors (often
called a Darlington pair). Darlington pair consists of two bipolar transistors such that the
current amplified by the first is amplified further by the second to get a high current gain ß or
hfe. The figure shown below is one of the eight Darlington pairs of ULN 2803 IC.
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Fig 3.5. DARLINGTON PAIR
Now 2 cases arise:-
Case 1: When IN is 0 volts.
Q1 and Q2 both will not conduct as there is no base current provided to them. Thus, nothing
will appear at the output (OUT).
Case 2: When IN is 5 volts.
Input current will increase and both transistors Q1 and Q2 will begin to conduct. Now, input
current of Q2 is combination of input current and emitter current of Q1, so Q2 will conduct
more than Q1 resulting in higher current gain which is very much required to meet the higher
current requirements of devices like motors, relays etc. Output current flows through Q2
providing a path (sink) to ground for the external circuit that the output is applied to. Thus,
when a 5V input is applied to any of the input pins (1 to 8), output voltage at corresponding
output pin (11 to 18) drops down to zero providing GND for the external circuit. Thus, the
external circuit gets grounded at one end while it is provided +Vcc at its other end. So, the
circuit gets completed and starts operating.
The interfacing between relay driver IC and relay is shown in figure 11 below:
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Fig. 3.6. ULN 2803
3.7 RELAYS
A relay is an electrically operated switch. It allows one circuit to switch a second
circuit which is completely separated from the first. For example a low voltage battery circuit
can use a relay to switch a 230V AC mains circuit. There is no electrical connection inside
the relay between the two circuits, the link is magnetic and mechanical.
Fig 3.7. RELAY
In the above figure, when controlling switch is closed, current flows through the
coil and thus, magnetic field is produced. The resulting magnetic field attracts an armature
that is mechanically linked to a set of contacts. The movement makes a connection with a
fixed contact and circuit gets completed. When the current to the coil is switched off, the
armature is returned by a force approximately half as strong as the magnetic force to its
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relaxed position and the connection is broken.
The relay's switch connections are usually labeled COM, N/C and N/O as shown
in figure 11 above:
• COM = Common, always connect to this; it is the moving part of the switch.
• N/C = Normally Closed, COM is connected to this when the relay coil is off.
• N/O = Normally Open, COM is connected to this when the relay coil is on.
Connect to COM and N/O if you want the switched circuit to be on when the relay coil is on.
Connect to COM and N/C if you want the switched circuit to be on when the relay coil is off.
3.8. POWER SUPPLY CIRCUIT
As in figure 3, this circuit is an approach to obtain both 12V and 5V DC
power supply. The circuit uses two ICs 7812(IC1) and 7805 (IC2) for obtaining the required
voltages. The AC mains voltage will be stepped down by the transformer T1, rectified by
bridge B1 and filtered by capacitor C1 to obtain a steady DC level .The IC1 regulates this
voltage to obtain a steady 12V DC. The output of the IC1 will be regulated by the IC2 to
obtain a steady 5V DC at its output. In this way both 12V and 5V DC are obtained. Such a
circuit is very useful in cases when we need two DC voltages for the operation of a circuit.
7812 IC 7812 is a famous IC which is being widely used in 12V voltage regulator
circuits.
Fig. 3.8. 7812 IC
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7805 IC
7805 is a famous IC which is being widely used in 5V voltage regulator
circuits.
Fig. 3.9. 7805 IC
3.8Flip Flops
In electronics, a flip-flop or latch is a circuit that has two stable states and can be used to
store state information. A flip-flop is abistable multivibrator. The circuit can be made to
change state by signals applied to one or more control inputs and will have one or two
outputs. It is the basic storage element in sequential logic. Flip-flops and latches are a
fundamental building block of digital electronicssystems used in computers, communications,
and many other types of systems.
Flip-flops and latches are used as data storage elements. Such data storage can be used for
storage of state, and such a circuit is described as sequential logic. When used in a finite-state
machine, the output and next state depend not only on its current input, but also on its current
state (and hence, previous inputs). It can also be used for counting of pulses, and for
synchronizing variably-timed input signals to some reference timing signal.
Flip-flops can be either simple (transparent or opaque) or clocked (synchronous or edgetriggered);
the simple ones are commonly called latches. The word latch is mainly used for
storage elements, while clocked devices are described as flip-flops.
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Flip-flops can be either simple (transparent or asynchronous) or clocked (synchronous);
the transparent ones are commonly called latches. The word latch is mainly used for storage
elements, while clocked devices are described asflip-flops.
Simple flip-flops can be built around a pair of cross-coupled inverting elements: vacuum
tubes, bipolar transistors, field effect transistors, inverters, and inverting logic gates have all
been used in practical circuits. Clocked devices are specially designed for synchronous
systems; such devices ignore their inputs except at the transition of a dedicated clock signal
(known as clocking, pulsing, or strobing). Clocking causes the flip-flop to either change or
retain its output signal based upon the values of the input signals at the transition. Some flipflops
change output on the rising edge of the clock, others on the falling edge.
Since the elementary amplifying stages are inverting, two stages can be connected in
succession (as a cascade) to form the needed non-inverting amplifier. In this configuration,
each amplifier may be considered as an active inverting feedback network for the other
inverting amplifier. Thus the two stages are connected in a non-inverting loop although the
circuit diagram is usually drawn as a symmetric cross-coupled pair (both the drawings are
initially introduced in the Eccles–Jordan patent).
Flip-flops can be generalized in at least two ways: by making them 1-of-N instead of 1-
of-2, and by adapting them to logic with more than two states. In the special cases of 1-of-3
encoding, or multi-valued ternary logic, these elements may be referred to as flip-flap-flops.
In a conventional flip-flop, exactly one of the two complementary outputs is high. This
can be generalized to a memory element with N outputs, exactly one of which is high
(alternatively, where exactly one of N is low). The output is therefore always a onehot
(respectively one-cold) representation. The construction is similar to a conventional
cross-coupled flip-flop; each output, when high, inhibits all the other outputs. Alternatively,
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more or less conventional flip-flops can be used, one per output, with additional circuitry to
make sure only one at a time can be true.
Another generalization of the conventional flip-flop is a memory element for multi-valued
logic. In this case the memory element retains exactly one of the logic states until the control
inputs induce a change. In addition, a multiple-valued clock can also be used, leading to new
possible clock transitions.
3.9 4017 Decade Counter
The 4017B is an integrated circuit which has been designed to count pulses. It has 16 pins
and looks like any other 16 pin integrated circuit.
They can be used in timing circuits and are often used to switch on and off LEDs or
motors or other circuits. They are versatile and relatively simple to put together. Counters
such as the 4017B are cheap and yet surprisingly useful.
The 4017B is most useful when combined with a timer such as a 555 based circuit. The
pulse from the 555 timer can be used to activate the 4017B circuit.
A good example is seen below. A 555 astable circuit is used to pulse the 4017B at regular
intervals. The pulse from the 555 IC is generated from pin 3. In the circuit seen below, pin
3 of the 555 IC feeds into pin 14 of the 4017B (called ‘clock in’). When this occurs pin
‘A’ of the 4017B emits current, lighting its LED. The next pulse from the 555 IC results in
pin ‘B’ of the 4018B IC emitting current and lighting its LED.
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Fig. 3.10. 4017
You can use the 4017 to control a sequence of events, for example, to generate a traffic light
sequence:
sequence
step
input
B
input
A output
0 0 0 1
1 0 0 1
2 0 0 1
3 0 0 1
4 0 1 0
5 1 0 0
6 1 0 0
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7 1 0 0
8 1 0 0
9 1 1 0
This pattern shows the lights green or red for a suitably long time, with amber and red+amber
illuminated for shorter periods.
The 4000 series is a family of industry standard integrated circuits (IC) which
implement a variety of logic functions usingComplementary Metal–Oxide–
Semiconductor (CMOS) technology, and are still in use today. They were introduced
by RCA asCD4000 COS/MOS series in 1968, as a lower power and more versatile alternative
to the 7400 series of TTL logic chips.[1] Almost all IC manufacturers active during the era
fabricated chips from this series. RCA sometimes advertised the line as COSMOS, standing
for COmplementary Symmetry Metal-Oxide Semiconductor. The naming system followed
the RCA convention of CA for analog, CD for digital, but did not relate to the Texas
Instruments SN7400 series numbering scheme.
Fig. 3.11. The CD4007 on a breadboard
4000 series parts have the advantage of lower power consumption, wider range of
supply voltages (3 V to 15 V), and simpler circuit design due to the vastly increased fan out.
However their slower speed (initially about 1 MHz operation, compared with bipolar TTL's
10 MHz) limits their applications to static or slow speed designs. New fabrication technology
has largely overcome the speed problems, while retaining backward compatibility with most
circuit designs. Although all semiconductors can be damaged by electrostatic discharge, the
high impedance of CMOS inputs makes them more susceptible than bipolar transistor-based,
TTL, devices. Eventually, the advantages of CMOS (especially the later series such as 74HC)
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edged out the older TTL chips, but at the same time ever increasing LSI techniques edged out
the modular chip approach to design. The 4000 series is still widely available, but perhaps
less important than it was two decades ago.
The series was extended in the late 1970s and 1980s to include new types which implemented
new functions, or were better versions of existing chips in the 4000 series. Most of these
newer chips were given 45xx and 45xxx designations, but are usually still regarded by
engineers as part of the 4000 series.
In the 1990s, some manufacturers (e.g. Texas Instruments) ported the 4000 series to their
newer HCMOS technology with devices such as the 74HCT4060 providing equivalent
functionality to a 4060 IC but with greater speed.
The 4000 series integrated circuits have been used in space satellites for many decades.
The original 4000 series was available in either unbuffered or buffered inputs and
outputs. The buffered outputs can source or sink more current than the unbuffered outputs,
eliminating the need for discrete switching transistors in some designs. The buffered versions
also have faster output switching times, as the signal rise time of the buffered output stage is
faster than that of an unbuffered device. However the overall propagation delay through the
buffered versions is higher due to the additional circuitry.[4][5] The buffered devices are more
susceptible to output oscillation with slow-changing inputs. Designers must evaluate the
choice of buffered or unbuffered parts according to the nature of the circuit in which the
devices are being used. The additional input and output gates on the buffered parts also make
them marginally less susceptible to damage by electrostatic discharge(ESD).
Although the original designation for unbuffered and buffered parts was the addition
of an 'A' or 'B' suffix to the part code (e.g.: 4000A = unbuffered, 4000B = buffered), some
manufacturers (e.g.: Texas Instruments) later changed to using UB (unbuffered) and B
(buffered) suffixes (e.g.: 4000UB and 4000B).
The diagrams below show the construction differences between a simple buffered and
unbuffered CMOS NOR logic gate. Note that the logic gate at the core of the buffered part is
actually a NAND gate, but the overall function of the complete circuit is a NOR gate due to
the logic inversions performed by the buffers. (A negated NAND with negated inputs
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becomes a NOR as defined by De Morgan's laws in Boolean Algebra.) The
clamping diodes on the inputs are to offer some protection against ESD.
The 4000 series permits the use of "cookbook" design, where standard circuit
elements can be created, shared, and connected to other circuits with few, if any, connection
difficulties. This greatly speeds the design of new hardware by reusing standard approaches
to circuit design. In contrast, TTL circuits, while similarly modular, often require much more
careful interfacing, since the limited fanout (and fan-in) require that the loading of each
output be carefully considered. (Some later TTL families, like 74LS reduce this problem with
fanouts of 20.) It is also much easier to prototype LSI designs using the 4000 series and get
repeatable and transferable results when moving to the more integrated design.
Some care needs to be taken with the design of circuits using CMOS chips. Many
parts offer multiple logic gates in a single package and it is common to not need all of them.
An engineer who forgets to 'tie off' (connect the unused gate inputs to VSS or VDD) may find
the chip draws excessive current. The problem is caused by biasing in each gate. With the
inputs disconnected, the gates may be biased into a mode where the outputs are partially
conducting; this leaves the output buffer drawing a great deal of current since it is not fully
on or off, creating a low resistance current path between the power supply rails.
4017 decade counter
The 4017 IC is a 16-pin CMOS decade counter from the 4000 series. It takes clock pulses from the
clock input, and makes one of the ten outputs come on in sequence each time a clock pulse arrives.
Pinout
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Fig. 3.12. PIN Diagram of 4017
Pin
number
Name Purpose
1 6 The 6th sequential output
2 2 The 2nd sequential output
3 1 The 1st sequential output
4 3 The 3rd sequential output
5 7 The 7th sequential output
6 8 The 8th sequential output
7 4 The 4th sequential output
8
0 V,
VDD
The connection to the 0 V rail
9 9 The 9th sequential output
10 5 The 5th sequential output
11 10 The 10th sequential output
12 CO
Carry out output - outputs high on counts 0 to 4, outputs low on counts 5 to 9
(thus a transition from low to high occurs when counting from 9 back to 0)
13 LE
Latch enable - latches on the current output when high (i.e. the chip counts when
LE is low)
14 CLK Clock in
15 RST Reset - sets output 1 high and outputs 2 through 10 low, when taken high
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+9 V,
VCC
The connection to the +VCC rail (voltage between +3 V and +15 V)
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3.10 LM394
The LM194 and LM394 are junction isolated ultra well- matched monolithic NPN
transistor pairs with an order of magnitude improvement in matching over conventional
transistor pairs. This was accomplished by advanced linear processing and a unique new
device structure.
Electrical characteristics of these devices such as drift versus initial offset voltage,
noise, and the exponential relationship of base-emitter voltage to collector current closely
approach those of a theoretical transistor. Extrinsic emitter and base resistances are much
lower than presently available pairs, either monolithic or discrete, giving extremely low noise
and theoretical operation over a wide current range.
Most parameters are guaranteed over a current range of 1 mA to 1 mA and 0V up to
40V collector-base voltage, ensuring superior performance in nearly all applications. To
guarantee long term stability of matching parameters, internal clamp diodes have been added
across the emitter-base junction of each transistor. These prevent degradation due to reverse
biased emitter currentÐthe most common cause of field failures in matched devices. The
parasitic isolation junction formed by the diodes also clamps the substrate region to the most
negative emitter to ensure complete isolation between devices.
The LM194 and LM394 will provide a considerable improvement in performance in
most applications requiring a closely matched transistor pair. In many cases, trimming can be
eliminated entirely, improving reliability and decreasing costs. Additionally, the low noise
and high gain make this device attractive even where matching is not critical. The LM194
and LM394/LM394B/LM394C are available in an isolated header 6-lead TO-5 metal can
package. The LM394/LM394B/LM394C are available in an 8-pin plastic dual-in-line
package. The LM194 is identical to the LM394 except for tighter electrical specifications and
wider temperature range.
3.11 Encoding & Decoding
In simple words, encoding is wrapping up the data. The data could be anything like
simple binary data (in the form of 1's and 0's) or it could be an audio signal or it could be
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certain text. But here we are dealing with the encoding that is used for binary signals. The
wrapped data is called as a Packet. This packet is sent through a medium (“Through wire or
wireless”) to the decoder part where it gets unwrapped or decoded. Yes, now what you are
thinking is right, it is exactly similar to posting an envelope. Encoding is when you put the
letter into envelope, the postman is medium to take the envelope to the recipient and when
recipient opens the envelope then it is called decoding.
So, essentially to apply encoding and decoding technique in our digital world we need
three entities: (1). A sender or in electronics sense it is Transmitter. (2). To receive this sent
data we need a receiver. (3). and of course we need an address of the receiver. The role of
address in electronics is played by address lines.
HT12D and HT12E
In today’s episode, I am taking an Encoder-decoder IC pair. In market, it is available
with the name as HT12E and HT12D. The ‘12’ in the name means 8-address lines and 4-data
lines while E and D letters represents ‘Encoder and decoder’ respectively.
HT12E(Transmitter side)
Fig. 3.13. HT12E
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Let’s first take the Encoding side. The encoder has four input lines. Theses lines are
used to give input which we want to encode. In encoding, we are wrapping up the data which
means if we want to send a binary signal ‘1001’ to other end, we have to make data pins as
‘1001’. Now, to make data pin like this, what we need to do is to give high or 5 volts (which
in digital means ‘1’) to pins ‘D0’ and ‘D3’ while we have to provide pins ‘D1’ and ‘D2’ with
0 volt. (Ground). This altogether gives us ‘1001’ which is transmitted out from the ‘Data out’
pin of the HT12E. The input given to data pin is in parallel form which is being transmitted
into serial form from the data output pin. The figure below will clear this:
Fig. 3.14. HT12E connections
Our data is now been encoded and will be transmitted. The transmission medium could be
anything, it could be our regular wire, or wireless. In this tutorial, we are going to use our
steady single core wire which we use to provide connections in breadboard (nothing fancy!).
27
The data flows in serial form through the wire and reaches the other end i.e. to the receiver.
Receiver now decodes this signal. So, let’s see how decoder works:
HT12D (Receiver side):
Below is the pin diagram of HT12D decoder IC.
Fig. 3.15. HT12D
Now neglect all the pins for this moment and just concentrate on Din (Data in) pin
and the for Data lines pin. The encoded data which is coming from the transmitter side goes
into the Data in (Din) pin. The data which was in serial order gets decoded and the output is
generated at the for data line pins in same order as that on transmitter pin.
Yup also remember: When there is no input at the data in pin, the output pins i.e. data
lines remains high.
The figure below shows the decoding taking place in HT12D
28
Fig. 3.16. HT12D Connections
Role of Address Lines:
When using a single pair of encoder-decoder IC, we generally leave the address pins
as it is i.e. we do not connect them to either ground or VCC. But what if there is more than
one decoder but only single encoder. In that case we need to give an address to the data that it
might travel to specific decoder only and our data should not leak at unnecessary decoders.
This is very useful in wireless communication.
To define an address, what we need to do is to connect specific address pins to the
ground on both encoder and decoder side; remember that the order of connecting the address
pins to the ground must be same. See the animation below for; it will remove all the twists in
your mind:
29
CHAPTER 4
FLOW CHART
FOR TRANSMITTER CIRCUIT
IR Signals
555 ASTABLE
MULTIVIBRATOR
SWITCHES
IR LEDS
30
FOR RECEIVER CIRCUIT
IR Signals
IR MODULE TSOP 1738
IC 4017 DECADE
COUNTER
5V RELAY
HOME APPLIANCES
31
CHAPTER 5
PCB MANUFACTURING
The PCB must be fabricated first. Then the components are soldered carefully to
PCB. We should keep in mind that the quality of soldering affects the quality of output. The
procedure for fabricating the PCB for setting up the circuit of any multipurpose project is
described below.
5.1 PCB MAKING
Making of Printed Circuits Boards (PCBs) is as much as art on a technique
particularly so when they are to fabricated in very small numbers. There are sever always of
drawing PCB patterns and making the final boards. The making of PCB patterns and making
PCB
essentially involves two steps.1. Preparing the PCB drawing and2.Fabricating the PCB
itself from the drawing. The traditional method of drawing with complete placement of
parts, taking a photographic negative of the drawing, developing the image of negative
formed on photosensitized copper plate and dissolving the excess copper by itching is a
standard practice being followed in large scale operations. However, for small-scale
operations, where large numbers of copies are not required, the cost saving procedure
presented here may be adopted.
5.2 PCB DRAWING
Making of PCB drawing involves some preliminary considerations such as placement
of components on a piece of paper. Locating holes, deciding the diameters of various holes,
the optimum area of each components should occupy the shape and location lands for
connecting two or more components at a place, full space utilization and prevention of
overcrowding of components at a particular place. The another way to arrive at the
conclusion than by trial and
error. For anchoring leads of component 1mm diameter holes and for fixing PCB holdings
crews to the 3mm diameter holes can be made. Following these hints, a sketch of PCB is
made.
32
5.3 PCB FABRICATION
The first step of assembling is to produce a printed circuit board. The fabrication of
the program counter plays a crucial role in the electronic field. The success of the circuit is
also dependent on the PCB. As far as the cost is concerned, more than 25% of the total cost is
for the PCB design and
fabrication.
The board is designed using a personal computer. The layout is drawn using the
software “Adobe PageMaker 6.5”. The layout is printed in a “buffer sheet” using a laser
procedure. First, a negative screen of the layout is prepared with the help of a professional
screen printer. Then the copper clad sheet is kept under this screen. The screen printing ink is
poured on the screen and brushed through the top of the screen. The printed board is kept
under shade for few hours till the ink becomes dry.
The etching medium is prepared with the un-hydrous ferric chloride water. The printed
board is kept in this solution till the exposed copper dissolves in the solution fully. After that
the board is taken out and rinsed in flowing water under a tap. The ink is removed with solder
in order to prevent oxidation.
Another screen, which contains component side layout, is prepared and the same is
printed on the component side of the board. A paper epoxy laminate is used as the board.
Both the component and the track layout of the peripheral PCB is given at the end of this
report.
The first step of assembling is to produce a printed circuit board. The fabrication of the
program counter plays a crucial role in the electronic field. The success of the circuit is also
dependent on the PCB. As far as the cost is concerned, more than 25% of the total cost is for
the PCB design and fabrication.
The board is designed using a personal computer. The layout is drawn using the
software “Adobe PageMaker 6.5”. The layout is printed in a “buffer sheet” using a laser
procedure. First, a negative screen of the layout is prepared with the help of a professional
screen printer. Then the copper clad sheet is kept under this screen. The screen printing ink is
poured on the screen and brushed through the top of the screen. The printed board is kept
under shade for few hours till the ink becomes dry.
33
The etching medium is prepared with the un-hydrous ferric chloride water. The printed
board is kept in this solution till the exposed copper dissolves in the solution fully. After that
the board is taken out and rinsed in flowing water under a tap. The ink is removed with solder
in order to prevent oxidation.
Another screen, which contains component side layout, is prepared and the same is
printed on the component side of the board. A paper epoxy laminate is used as the board.
Both the component and the track layout of the peripheral PCB is given at the end of this
report.
34
5.4 PCB Layout
35
5.5 3D View
36
CHAPTER 6
FINAL IMPLEMENTATION
37
CHAPTER 7
RESULT ANALYSIS & DISCUSSION
By designing this Project we can aware about the working of Remote Controlled
Home Appliances and we can advance this instrument at low cost by developing its
features with some components.
The main application of this circuit is that we can control any appliance by just being
in our living room. This is very much helpful for elderly people as well as for those who are
unable to walk either due to physical disabilities or due to accidents. This circuit enables us to
control appliances in the top floor also.
Another major use of our project is that we can turn off the operating devices all
together at one shot by just pressing the power button.
38
CHAPTER 8
CONCLUSION & FUTURE WORK
Hereby we come to an end of or project “remote controlling of home appliances”.
This project gives us an idea of RC5 Protocol and the microcontroller AT89C2051. This
project can be used anywhere either at home or offices. This is also cost efficient. Thus by
this attempt of ours the ON/OFF processes of many devices was successfully carried out by
just using a TV remote.
The circuit can be modified to control all functions of a particular device like the TV
remote controlling all processes of a television. Also the program can be altered to control the
ON/OFF processes of more than eight appliances.
39
REFERENCES
[1]http://arif-ece.blogspot.com/2010/05/circuit-for-controlling-8-appliances.html
[2]http://www.8051projects.net/out.php?link=http://www.ustr.net/infrared/infrared1.shtml
[3] The 8051 microcontroller - Kenneth J. Ayala
[4] Ahmed M. S., Mohammed A. S., Onimole T. G., Attah P. O., Leonardo Electronic
Journal of Practices and Technologies,9,p.55-62, 2006.
[5] Mahmud S. A., Murtala B. Z. A., Kolo J.G., Leonardo Journal of Sciences, 11, p. 41-50,
2007.
[6] Kolo J. G., Daudad U.S., Leonardo Journal of Sciences, 7, p. 175-186 2008.
[7] Bergmans S., Oisterwijk, Sony SIRC Protocol [online]. Available at:
http://www.sbprojects.com/knowledge/ir/sirc.htm.
[8] Philips Semiconductors Application note, Power Control with Thyristors and Triacs
[online]. Available at: http://www.fairchildsemi.com/an/AN/AN-3006.pdf
[9] Finney D., The Power Thyristor and its Applications, p. 35, Toronto, McGraw-Hill Book
Company Limited, 1980.
[10] Richard H.B.,Embedded C Programming and the Atmel AVR, Clifton Park, NY
Thomson Delmar Learning, 2006.
[11] Pranav Kumar Asthana, Advances in Applied Science Research, 2010, 1 (2), pp. 84-91.
[12] Ochala, I. , Momoh, O. Y. and Gbaorun, F., Advances in Applied Science Research,
2011, 2 (2),pp.28-37.
[13] Shahanaz Ayub, J.P.Saini, Advances in Applied Science Research, 2010, 1(2), pp. 76-
83.
[14] Ofoefule, Akuzuo U. , Nwankwo, Joseph I. and Ibeto, Cynthia N., Advances in Applied
Science Research, 2010, 1 (2),pp.1-8
[15] Nhivekar G.S., Mudholkar R.R., Journal of Electrical and Electronics Engineering,
2011,4(1), pp.139-142.
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