Mini project Report On
DTMF Tele switch
CONTENTS
Sl No. Contents Page No
1. Cover Page 2
2. Certificate 3
3. Acknowledgement 4 4. Contents 5
5. Abstract 6
6. Introduction 7
7. Block Diagram 8
8. Circuit Diagram
9. Components Description
10. Circuit Description
12. Results & Conclusion
13. Future Scope
14 Reference
APPENDIX
Data sheets
ABSTRACT
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.
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.
INTRODUCTION
The aim of the proposed system is to develop a cost effective solution that will provide controlling of home appliances remotely and enable home security against intrusion in the absence of homeowner. The system provides availability due to development of a low cost system. The home appliances control system with an affordable cost was thought to be built that should be mobile providing remote access to the appliances and allowing home security. Though devices connected as home and office appliances consume electrical power. These devices should be controlled as well as turn on/off if required. Most of the times it was done manually. Now it is a necessity to control devices more effectively and efficiently at any time from anywhere.
In this system, 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.
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.
BLOCK DIAGRAM
CIRCUIT DIAGRAM
Power Supply Circuit:
Control Circuit:
WORKING:
The working of the circuit is quite simple and easily understandable by jus observing the circuit. The working can be mainly discussed as three parts which are the supply part, micro-controller part and the isolation part respectively. All these parts together describe the working of the design of Home automation system.
The supply part/section mainly deals with the supply given to the circuit. Actually it can be done in two ways i.e., either by giving 230V AC or by using a battery (9V) as source of supply. Now in this design we are using a 9V battery as source of supply. This 9v is regulated to 5V using a voltage regulator as only 5V is required to drive the microcontroller. This 5V is also given to the receiver. Actual working of this system involves an RC5 remote which is used as Transmitter and TSOP1738 as IR receiver. And here we are designed the system for only 6 applications. So only 6 buttons are used in the RC5 remote. Each button is given certain address depending on the number of duty cycles it has for 1ns. When a button is pressed, say 1, the receiver receives the signal from the RC5 remote and the next operation is done by the micro-controller part.
In micro-controller section, there are mainly 2 parts. They are AT89C2051 micro-controller and ULN 2003 driver (Darlington transistor). The microcontroller intakes the received signal from the IR receiver (TSOP 1738). The main use of this controller is that it recognizes and counts the number of duty cycles the received signal has and then makes the respective output pin high according to the calculations done by it internally. For example, let us consider that the button 1 has 1500 duty cycles in 1nS. When this button is pressed, the transmitter in the remote sends this signal and the receiver receives the signal. The received signal also contains same number of duty cycles but the micro controller confirms it with the help of the external timers it has. After confirmation, the controller makes the first output high. Here both the transmitter and receiver are of Infrared type. This output is connected to Darlington transistor (ULN 2003) which is used to drive the application. This gives a much higher current gain and also improves the life of the microcontroller. All the six out puts of micro controller are given as input to the Darlington transistor/pair IC which improves the gain of those outputs and gives the respective six outputs. These outputs are connected to the Opto-Isolator which is discussed in the isolation part.
The Isolation part involves the isolation of the AC and DC i.e., the output from the controller is DC and the Input to the application required is AC and to make difference of this nature of supply, an Opto isolator (MOC 3021) is used in between them. The MOC 3021 IC consists of a The input to the isolator is taken from the Darlington transistor IC. The pin1 of this Isolator IC is given to the supply or is in High state and the second pin is grounded. The output from the ULN2003 IC is connected to the second pin of the MOC 3021 IC which is low. The IC internally consists of a LED and a DIAC. Whenever the led glows, the DIAC gets triggered and hence fires the gate of the TRIAC connected to the IC. A feedback resistance is used for this operation.
Let us assume that a bulb is used as application here. One terminal of this bulb is connected to the AC supply and the other is connected to the TRIAC. When the TRIAC gets fired the bulb glows. This is the working of the Home Automation System using IR signal.
COMPONENTS USED:
1. Rectifier(IN4007 Diodes)
2. Voltage Regulator
3. TSOP 1738
4. Crystal oscillator
5. Triac bt136
6. Moc 3021
7. ULN 2003.
8. 2051 Uc
9. RTC
COMPONENTS DESCRIPTION
1.Rectifier
Rectifier circuits are found in all dc power supplies that operate from an ac voltage source. They convert the ac input voltage to a pulsating dc voltage. The most basic type of rectifier circuit is the half-wave rectifier. Although half-wave rectifiers have some applications, the full-wave rectifiers are the most commonly used type in dc power supplies. These are two types of full-wave rectifiers:
(1) full-wave center-tapped rectifier
(2) full-wave bridge rectifier
Here in this particular design we are using a bridge rectifier which is discussed as follows.
Full-wave Bridge Rectifier
The full –wave bridge rectifier uses four diodes, as shown in below figure. When the input cycle is positive, diodes D1 and D2 are forward-biased and conduct current through RL. During this time, diodes D3 and D4 are reverse-biased.
During positive half-cycles of the input, D1 and D2 are forward-biased and conduct current, D3 and D4 are reverse-biased.
When the input cycle is negative as shown in below figure, diodes D3 and D4 are forward-biased and conduct current in the same direction through RL as during the positive half-cycle. During the negative half-cycle, D1 and D2 are reverse-biased. A full-wave rectifier output voltage appears across RL as a result of this action.
During negative half-cycles of the input, D3 and D4 are forward-biased and conduct current, D1 and D2 are reverse-biased.
The above two figures explain the full-wave Bridge Rectifier.
The output graph of a full-wave rectifier is as shown below:
The diodes used in this rectifier are IN4007 which is discussed below.
IN4007 Diode
These diodes are used to convert AC into DC these are used as half wave rectifier or full wave rectifier. Three points must he kept in mind while using any type of diode.
1. Maximum forward current capacity
2. Maximum reverse voltage capacity
3. Maximum forward voltage capacity
The number and voltage capacity of some of the important diodes available in the market are as follows:
· Diodes of number IN4001, IN4002, IN4003, IN4004, IN4005, IN4006 and IN4007 have maximum reverse bias voltage capacity of 50V and maximum forward current capacity of 1 Amp.
· Diode of same capacities can be used in place of one another. Besides this diode of more capacity can be used in place of diode of low capacity but diode of low capacity cannot be used in place of diode of high capacity. For example, in place of IN4002; IN4001 or IN4007 can be used but IN4001 or IN4002 cannot be used in place of IN4007.The diode BY125made by company BEL is equivalent of diode from IN4001 to IN4003. BY 126 is equivalent to diodes IN4004 to 4006 and BY 127 is equivalent to diode IN4007.
2.Voltage Regulator
A voltage regulator is an electrical regulator designed to automatically maintain a constant voltage level. It may use an electromechanical mechanism, or passive or active electronic components. Depending on the design, it may be used to regulate one or more AC or DC voltages.
With the exception of passive shunt regulators, all modern electronic voltage regulators operate by comparing the actual output voltage to some internal fixed reference voltage. Any difference is amplified and used to control the regulation element in such a way as to reduce the voltage error. This forms a negative feedback servo control loop; increasing the open-loop gain tends to increase regulation accuracy but reduce stability (avoidance of oscillation, or ringing during step changes). There will also be a trade-off between stability and the speed of the response to changes. If the output voltage is too low (perhaps due to input voltage reducing or load current increasing), the regulation element is commanded, up to a point, to produce a higher output voltage - by dropping less of the input voltage (for linear series regulators and buck switching regulators), or to draw input current for longer periods (boost-type switching regulators); if the output voltage is too high, the regulation element will normally be commanded to produce a lower voltage. However, many regulators have over-current protection, so entirely stop sourcing current (or limit the current in some way) if the output current is too high, and some regulators may also shut down if the input voltage is outside a given range (see also: crowbar circuits).
The voltage Regulator used in this design is LM 7812.
LM78xx Regulator
The LM78XX series of three terminal regulators is available with several fixed output voltages making them useful in a wide range of applications. One of these is local on card regulation, eliminating the distribution problems associated with single point regulation. The voltages available allow these regulators to be used in logic systems, instrumentation, Hi-Fi, and other solid state electronic equipment.
Although designed primarily as fixed voltage regulators these devices can be used with external components to obtain adjustable voltages and currents. The LM78XX series is available in an aluminum TO-3 package which will allow over 1.0A load current if adequate heat sinking is provided. Current limiting is included to limit the peak output current to a safe value. Safe area protection for the output transistor is provided to limit internal power dissipation.
If internal power dissipation becomes too high for the heat sinking provided, the thermal shutdown circuit takes over preventing the IC from overheating. Considerable effort was expanded to make the LM78XX series of regulators easy to use and minimize the number of external components. It is not necessary to bypass the output, although this does improve transient response. Input bypassing is needed only if the regulator is located far from the filter capacitor of the power supply.