This project is intended to save the 'led display' costs (eg: at railway station).The display built by me costs not more than Rs 1000/- .The main principle used is persistence of vision and ghosting. For proper synchronization and timing we need some feedback from the rotating assembly ,thus to make the system closed loop infrared encoder is used to detect reference position of assembly .The power lines to the rotating assembly have been made available through brush contacts .Three keys are used for user interface to select his text.The character resolution is of 5X8 maximum word length is of 9 characters with a refresh rate of 20Hz
The components used are micro-controller P89V51RD2FN, LM 358, IR trans reciever pair, 7805, 12V motor, crystal 11.0592 MHz, resistors capacitors LED's etc .The main reason behind using the mentioned micro-controller is that it has a built-in ISP with its diagram as shown ( just refer the the diagram use Google translate if needed ), so you can program the micro-controller without replacing it in the programmer, making the job of programming a bit comfortable.
The programming is quite simple .Here I am polling P1.3 continuously and whenever poll condition satisfies it displays pixel data sequentially after some delay which defines pixel size.
