Microcontroller remote controlling project
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This project aims to remotely control home appliances using a mobile phone. A caller can control appliances by pressing buttons on their phone, generating DTMF tones. These tones are decoded by a microcontroller which then activates relays connected to appliances. The microcontroller was programmed in C to activate relays corresponding to different DTMF tone combinations. This allows remote control of appliances from any phone.
Microcontroller remote controlling project
- 1. Project Presentation on DTMF Based Remote Controlling of Home Appliances Using Mobile Phone
- 2. ABSTRACT Aim of the project is to use a mobile phone to control home appliances. With this project a caller can remotely control home appliances by pressing different keypad buttons which generates identical DTMF signal. To get desired controlling output using Microcontroller.
- 3. Control of home appliances involves 3 different phases 1. Perception 2. Processing 3. Action INTRODUCTION
- 4. PERCEPTION First part is the decoding of DTMF tone generated by pressing a key in calling phone. Audio signal output from receiving phone is fed to DTMF decoder chip. Decoder chip converts DTMF tone into binary codes to be fed to Microcontroller.
- 5. PROCESSING After perception stage, microcontroller processes the binary codes it receives Microcontroller is pre-programmed in ”C” to perform specific task according to input bits. Program is written in AVR Studio and Simulated in Proteus7.7 software.
- 6. ACTION Final stage is to switching ON/OFF the home appliances connected across the main power line of 220 V 50 Hz AC. For switching purpose electromagnetic Relays were used.
- 7. BASIC BLOCK DIAGRAM OF THE PROJECT Figure 1. Basic block diagram of the project (ref.p-4 )
- 8. DTMF- Dual Tone Multi Frequency. • DTMF is the signal that generates upon pressing an ordinary telephone’s any keypad button. • Signal generated by the superposition of two pure sinusoidal tones. • One is high frequency & another is low frequency tone signal.
- 9. 1 2 3 697 4 5 6 770 7 8 9 852 * 0 # 941 1209 1336 1477 Frequency(Hz) Each button lies at the intersection of the two tones Table 1- Row and column frequency correspondence
- 10. Structure of 8870 DTMF decoder Figure 2- Structure of 8870 DTMF decoder (ref. p-6 )
- 11. DTMF Decoder 8870 Decodes DTMF signals & converts into binary bits Button Low Frequency(Hz) High Frequency(Hz) Q1 Q2 Q3 Q4 1 697 1209 0 0 0 1 2 697 1336 0 0 1 0 3 697 1477 0 0 1 1 4 770 1209 0 1 0 0 5 770 1336 0 1 0 1 6 770 1477 0 1 1 0 7 852 1209 0 1 1 1 8 852 1336 0 0 0 0 9 852 1477 1 0 0 1 0 941 1209 1 0 1 0 * 941 1336 1 0 1 1 # 941 1477 1 1 0 0 Table 2- Values of decoder output for various frequencies
- 12. ATmega 16 Microcontroller Features High performance, Low power 8 bit Microcontroller. 16 KB Flash Memory with read and write capabilities. 512 Bytes EEPROM. 1 KB Internal RAM. 32*8 General purpose working Registers. Three timers. Internal/ External Interrupts.
- 13. Working Procedure The operation is initiated by calling the second mobile phone at receiving end. Mobile at receiving end receives the DTMF signals, which is generated by pressing the keypad of caller mobile phone. DTMF signal is passed to the DTMF decoder IC 8870 and decodes binary outputs. Binary output is inverted using IC 7404. The inverted output is fed to the input PORT A of the Microcontroller. The Microcontroller then gives desired output as it was programmed. When any output pin of PORT D becomes high then connected corresponding Relay become active and it makes the circuit close to switch ON any circuit or Device.
- 14. Number pressed by user Output of DTMF decoder Input to microcontroller Output from microcontroller Action performed 2 0x02 0010 0x0D 1101 0x00 00000000 Both relays off 4 0x04 0100 0x0B 1011 0x01 00000001 One relay on 6 0x06 0110 0x09 1001 0x02 00000010 Another relay on 8 0x08 1000 0x07 0111 0x03 00000011 Both relays on Table 3-Actions performed corresponding to the key pressed
- 15. • Microcontroller program was written in C language on AVR Studio. • Program was converted into desired Hex file using AVR Studio. • Circuit was simulated in Proteus 7.7 Software Simulation circuit is given in Figure 3
- 16. Figure 3 – Simulation circuit using Proteus 7.7 (ref. p-13)
- 17. MAIN CIRCUIT DIAGRAM Figure 4- Main circuit diagram (ref. p-15)
- 18. RELAY Relay is an electromagnetic switch. It consists of a control coil and a load circuit. Control coil controls the operation and load circuit is a switch. Current flowing through the control coil creates a small magnetic field causes the load circuit switch to close and relay is then active.
- 19. Figure 5- Structural view of Relay.
- 20. Microcontroller output pin PD0 and PD1 are connected with relays through BC 547 transistor. When transistor becomes ON then relay also be active. A relay used as a switch of the home appliance which is connected across the main power supply 220 V- 50 Hz AC. Here two 220V – 10 W bulbs are used as home appliances.
- 21. APPLICATION The system can be used in controlling home appliances. Can be used in office, lab ,class and factory etc. This setup with a little modification can be adapted to the following applications 1) Combination Lock 2) Home Security System 3) Mobile / Wireless Robot control 4) Wireless Radio Control 5) Continuous monitoring of system status