Minor project ReportHome appliance control using RF module and DTMF

Project Guide: Ms. Bhawna Verma Submitted by: Harpreet singh(9910102311) Upendra kumar Sharma(10104705) Vivek yaduvanshi(9910102367)

INDEX Acknowledgement Abstract Flow chart of rf module Circuit diagram of transmitter Working of Transmitter Encoder Circuit diagram of receiver Working of receiver Decoder Atmel 8051 IC Introduction to 8051 Features of 8051 Future Aspect Bibliography

ACKNOWLEDGEMENTWe wish our heartfelt gratitude to the entire faculty of Department of Electronics and Communication, Jaypee Institute of Information Technology University, for their keen interest, encouragement, methodical approach, timely suggestions, enthusiastic guidance and faith in us. We deem it our privilege to have carried out the project under their able guidance. Also, our sincere thanks to our teacher Ms. Bhawna verma, Department of Electronics and Communication Engineering, for clearing our theoretical concepts regarding the subject which made the foundation of this project and providing relevant guidance in our endeavors.

Abstract It is a microcontroller based wireless equipment controller, that can switch on or switch off devices at a desire time interval. This system is a combination of software and hardware. We have used AT89C51 microcontroller kit for interfacing our system. This paper is about controlling various AC devices using remote control which is working on Radio frequency. Let us take an example, if we can connect the bulb at the output then we can switch on or off of bulb at a desire time interval using the remote. We are using RF transmission because with the help of IR transmitter there is a problem of directivity and range of working, that problem is eliminated with RF transmission. RF has better directivity and frequency range.

Flow chart of RF module

Circuit Diagram of Transmitter

Working of transmitterThis circuit consists of Transmitter and Receiver section. The circuit can be used to control home appliances within a range of 30 meters. In open area, you can expect a range of 100 meters. The circuit comprises HT12 Encoder. HT12 Encoder is used in the transmitter (remote) circuit where as HT12D is used in receiver circuit. The Encode IC encodes the 4 bits of data and transmits it serially to RF Transmitter module. These 433 MHz transmitter and receiver modules operate using ASK Modulation.

Encoder Ht12E

Working of EncoderHT12E is an encoder integrated circuit of 212 series of encoders. They are paired with 212 series of decoders for use in remote control system applications. It is mainly used in interfacing RF and infrared circuits. The chosen pair of encoder/decoder should have same number of addresses and data format. Simply put, HT12E converts the parallel inputs into serial output. It encodes the 12 bit parallel data into serial for transmission through an RF transmitter. These 12 bits are divided into 8 address bits and 4 data bits. HT12E has a transmission enable pin which is active low. When a trigger signal is received on TE pin, the programmed addresses/data are transmitted together with the header bits via an RF or an infrared transmission medium.

Encoder

Circuit Diagram of Receiver

Working of receiverThe converse operation happens in the receiver section. The serial information is given to the decode section and the ICHT12D decodes the 4 bit data and gives across the data pins. The devices are then connected using the ULN2803 high voltage high current buffer.

Decoder HT12D

Working of DecoderHT12D is a decoder integrated circuit that belongs to 212 series of decoders. This series of decoders are mainly used for remote control system applications, like burglar alarm, car door controller, security system etc. It is mainly provided to interface RF and infrared circuits. They are paired with 212 series of encoders. The chosen pair of encoder/decoder should have same number of addresses and data format.

Decoder

ATMEL 8051 IC

Introduction to 8051Intel Corporation fabricated the 8 bit microcontroller which was referred as MCS-51 in 1981. This microcontroller was also referred as system on a chip because it has 128 bytes of RAM, 4Kbytes of ROM, 2 Timers, 1 Serial port, and four ports on a single chip. The CPU can work for only 8bits of data at a time because 8051 is an 8-bit processor. In case the data is larger than 8 bits then it has to be broken into parts so that the CPU can process conveniently. Most manufacturers have put 4Kbytes of ROM even though the quantity of ROM can be exceeded up to 64 K bytes.

Features of 8051The main features of 8051 microcontroller are: RAM 128 Bytes (Data memory) ROM 4Kbytes (ROM signify the on chip program space) Serial Port Using UART makes it simpler to interface for serial communication Two 16 bit Timer/ Counter Input/output Pins 4 Ports of 8 bits each on a single chip. Interrupt Sources 8 bit ALU (Arithmetic Logic Unit) Harvard Memory Architecture It has 16 bit Address bus (each of RAM and ROM) and 8 bit Data Bus.

RelayWe have also used relay in our circuit to switch it on/off.A relay is a device that allows you to control a high-current electrical load with a low-current electrical 'signal'. They are usually electro-magnetic, but are also available in solid-state forms. They can be used with a switch (to allow control of a high-current load with a small switch) or they can be hooked up to a switched power source in the car like the ignition or accessory power circuits (to allow power to be switched on/off automatically with the ignition key).

5-point Relay

WORKING OF IC ULN2803IC 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.

Features

Eight Darlingtons with Common Emitter. Opencollector 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.

ULN2803

DTMF Cell Phone controlled Home appliances DTMF stands for Dual Tone - Multi Frequency and it is the basis for your telephone system. When you press the buttons on the keypad, a connection is made that generates two tones at the same time. A "Row" tone and a "Column" tone. These two tones identify the key you pressed to any equipment you are controlling Our project uses CM-8870 DTMF decoder IC which decodes tone generated by the keypad of cell phone. When you press any keys in your mobile Phone while call in progress, the other person will hear some tones with respect to keys pressed. These tones are based on the DTMF (Dual Tone Multi Frequency) technology. Data transmitted in terms of pair of tones. The receiver detects the valid frequency pair and gives the appropriate BCD code as the output of the DTMF decoder IC. DTMF signal can be tapped directly from the microphone pin of cell phone device.

DTMF DECODER IC

Future Aspect:Typical applications for RF modules include vehicle monitoring, remote controls, telemetry, small-range wireless networks, area paging, industrial data acquisition systems, wireless meter reading, access control systems, wireless home security systems, reading of radio tags, RF contact-less smart cards, wireless data terminals, wireless fire protection systems, robot remote control, wireless data transmissions, digital video/audio transmission, biological signal acquisition, hydrological and meteorological monitoring, digital home automation (ex: remote light switches), industrial remote controls, telemetry and remote sensing, alarm systems and wireless transmission for various types of low-rate digital signals, remote controls for various types of household appliances and electronics projects.

BIBLIOGRAPHY Muhammad A Mazidi for 8051 microcontroller George Kennedy for Electronics Communication Tata Mc Graw Hill for electronics Bernard Skalar, pabitra Kumar Ray for Digital Communication Sinha for Power Electronics, New Age. Digital and analog communication by B.P. lathi www.efy.mag.com www.engineersgarage.com