1. Bad driver Feedback display 40x16 LED matrix display https://docs.google.com/?pli=1#folders/0B5vWPuxrsdbDZjMyNjI0YWItZTg0OC00NzZjLTllZDItNDUyNjc2NTQ5 ZDk5 Documentation and Project files @

2. Idea How it came into my mind The project was made for displaying it on the rear glass shield of the car. It is designed in such a way that it will not obstruct the view for rear viewing mirror and also could display text and images to the following car. the idea came to my mind as often driving on highway it was required to give feedback to other (BAD) drivers, who does not follow highway rules...( Grrrrrrr )

3. Introduction Intro: LED matrix display has many variants, in terms of row and columns, types of LEDs, packing and the way they are driven. and application also.

4. Step 1 : Making of LED Matrix Dimensions : the rear wind shield of my car ( volkswagon polo )is approx 104x38 cm. So I decided to grid to 2 cm by 2cm. this will make it a almost cover whole that are of sheild and also grid is enough big so that it will not obstruct the view.

5. Step 1 : Making of LED Matrix Rows and Columns: Looking into the way to drive these leds and how to handle the program I concluded that it should be multiple of 8 ( as 74hc595 was decided ) I tried to get free sample from TI for MAX6952 and MAX6953 5x7 LED Drivers but vain. So i decided to make my own drivers. so the final grid was of 40x16 leds. this means 5 chips on col and 2 chips on rows.

6. Step 1 : Making of LED Matrix Dye for matrix: Since I wanted the spacing between LED to be perfect so i created a holder for the led and soldered them. This gave a good results in terms of spacing consistency. It was a waste piece of wood. Made slots in it as per led dimensions and then inserted leds in it bending there legs and then soldering it. step by step I made it modular process and it took two full days to make full matrix. It may sound large time but believe me it will take that....

7. Step 1 : Making of LED Matrix

8. Step 2 : LED Driver Circuit Driver for LED: Since I did some research on how to drive led and matrix.. so the easy and cheap way come to me was 74HC595 8-bit serial-in, serial or parallel-out shift register with output latches; 3-state. In above diagram there is a example of driving 8 rows. Similar it was extended for 16 rows.

9. Step 2 : LED Driver Circuit since I wanted it to have maximum transparency so I decided to omit the PCB for this and solder the components directly to the LED's. though it is not such a good option but i am happy with the result.. once done i dont need to move it alot..

10. Step 2 : LED Driver Circuit attaching all the components and dong wiring to it. the output was not as great i expected. but it was good for testing and prototyping.. the wires were looking very messy and not neat. may be should use thinner wires that may give some neat results... but still i go ahaead with this and created a program for driving this.

11. Step 2 : LED Driver Circuit Finally I run a test program to test all the LED. the output was thrilling and was happy to see the results

12. Step 3 : Programming Programming was done in assembly language and AT89C51 was used. Since it has limited RAM and ROM, managing resources became difficult with time as I was proceeding with code. I used Scratch pad ram for static Image of led. Timers for polling rows data. Interrupt for changing static images images. Data base in ROM for character generation and images...

13. Step 3 : Programming To run all the led was easy but to display some patterns required lots of TRICKS and special techniques for performance. Since I was using low speed processor. So it took lots of performance tuning was done.

14. Final output I was able to do lots of pattern and animations. text scrolling and smooth scrolling. etc etc.. there is a small video to show you results. https://picasaweb.google.com/lh/photo/BZinW0J5 OGr8WPkTF3- wcg?feat=directlink https://picasaweb.google.c om/lh/photo/_yIWMwC6D RjNl4BuxLqHtg?feat=direc tlink Video 1 Video 2

15. Final output Then it was installed on the back of car. currently it is showing hard code text but i have plans to update it from mobile via bluetooth, so that i can provide feedback to the following cars https://picasaweb.google.com/104475112007830 201673/LEDScroll#5664 874113381340482 https://picasaweb.google.c om/104475112007830201 673/LEDScroll#56648742 98273614306 Video 3 Video 4