dtmf based home appliance using microcontroller

Topics: Resistor, Switch, Electrical resistance Pages: 70 (20247 words) Published: October 8, 2013


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. AT89C51 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.


What is embedded system?
“An embedded system is a system that has software embedded into computer-hardware, which makes a system dedicated for an application (s) or specific part of an application or product or part of a larger system.” An embedded system is a microcontroller-based, software driven, reliable, real-time control system, autonomous, or human or network interactive, operating on diverse physical variables and in diverse environments and sold into a competitive and cost conscious market. An embedded system is not a computer system that is used primarily for processing, not a software system on PC or UNIX, not a traditional business or scientific application. High-end embedded & lower end embedded systems. High-end embedded system - Generally 32, 64 Bit Controllers used with OS. Examples Personal Digital Assistant and Mobile phones etc .Lower end embedded systems - Generally 8,16 Bit Controllers used with an minimal operating systems and hardware layout designed for the specific purpose.

System design calls

Embedded system design cycle

“V Diagram”

Characteristics of Embedded System
An embedded system is any computer system hidden inside a product other than a computer. They will encounter a number of difficulties when writing embedded system software in addition to those we encounter when we write applications. Throughput – Our system may need to handle a lot of data in a short period of time. Response–Our system may need to react to events quickly.

Testability–Setting up equipment to test embedded software can be difficult. Debugability–Without a screen or a keyboard, finding out what the software is doing wrong (other than not working) is a troublesome problem. Reliability – embedded systems must be able to handle any situation without human intervention. Memory space – Memory is limited on embedded systems, and you must make the software and the data fit into whatever memory exists. Program installation – you will need special tools to get your software into embedded systems. Power consumption – Portable systems must run on battery power, and the software in these systems must conserve power. Processor hogs – computing that requires large amounts of CPU time can complicate the response problem. Cost – Reducing the cost of the hardware is a concern in many embedded system projects; software often operates on hardware that is barely adequate for the job. Embedded systems have a microprocessor/ microcontroller and a memory. Some have a serial port or a network connection. They usually do not have keyboards, screens or disk drives.

1) Military and aerospace embedded software applications
2) Communication Applications
3) Industrial automation and process control software
4) Mastering the complexity of applications.
5) Reduction of product design time.
6) Real time processing of ever increasing amounts of data.
7) Intelligent, autonomous sensors.

Real Time Systems.
RTS is one which has to respond to events within a specified deadline. A right answer after the dead line is a wrong answer....

Bibliography: 1. The 8051 Micro controller and Embedded Systems
- Muhammad Ali Mazidi & Janice Gillispie Mazidi
2. Micro controllers Theory and Applications
- Ajay V. Deshmukh
3. www.wikipedia.org
4. www.8051.com
6. www.microcontroller.com
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