Control Appliance with Computer

A PROJECT REPORT ON HARDWARE INTERFACING 1. Introduction to project This project contains its own hardware and software to control at most eight electric appliances via PC’s parallel port. This project is independently developed by me. You can ON/OFF an appliance with Function keys (F1, F2, F3….) or with the help of mouse. This means if you have connected a fan on switch-3 and a bulb on switch on Switch-2 and if you want to OFF the fan you can do it by simply pressing F3 key. Again if you want to ON it you can do it by again pressing F3 key, without affecting state of bulb. 2. Aim of project Most of engineering industry using PC to control hardware with using additional I/O card but with my project you can use your default printer port controlling external device such as switching on/off light or control electronic devices. This project allows you to control appliance in your home or office like-turning on or off the air conditioner, adjusting lighting, opening & closing windows, monitoring burglar alarms, and more. 3. Requirements 3.1 System: - A PC working on MS-DOS/WINDOWS 98/ME 3.2 Software:-A program written in C. 3.3 Hardware:- This material is about the parallel port on MS-DOS / Windows computers. Imagine you are looking at the back of your pc, and that the parallel port socket is horizontal, with the long row of socket on top. The numbers of the sockets at the ends of the rows are... 13 . . . . . . . . . . 1 25 . . . . . . 14 The 'interesting' pins are: Data bits 0-7: Pins 2 to 9, respectively. If you write to address 888 (decimal), you should see the outputs on those pins change. Pins 18-25: Signal ground. (i.e. for a very simple experiment, connect an LED to pin2, a 680ohm resistor to the LED, and then the other end of the LED to pin 19. The PCB contains eight identical switched relay positions, Power input positions to the relays (either 2.5mm jack centre positive, or via the terminal block) and a Centronics connector to the parallel port of a PC. To keep the kit simple no input latches have been put on it. If your application is important then you should use a UPS to keep the computer operating in the case of a mains power supply failure. If the board is accidentally disconnected from the parallel port then the 10K pulldown resistors will turn the relay off. The diodes protect the transistors from the backemf which is occurs when the relay is turned off and its magnetic field collapses. The relays are under direct control of the output byte (8 bits) from the parallel port. When a pin is high a nominal 5V is presented to the base resistor R1. 3.4 COMPONENTS Components Specification Numbers Resistors 1Kohm 9 Capacitors 1uf,.1uf,1000uf 1,1,1 General Purpose Circuit Board 1 Relay 5 V. 8 25 Pin Male Connector D-Type 1 25 Pin Female Connector D-Type 1 L.E.D. Green 8 L.E.D. Red 9 I.C. LS7805 1 I.C. 74LS244 1 Transformer 6 V. 1 Diode IN4001 2 Wire Multicolor 5 mt. 4. Circuit Diagrams 4.1 Circuit for Regulating DC supply 4.2 Interfacing Parallel Port DESIGNE AND DEVLOPED BY : AMIT KAUSHIK