This project started because I had seen these signs and thought to my self
would it not be nice to have one of those things. But they were a bit to expensive.
The whole thing started me thinking on how the did this.
After reading some documents and searching the internet it was clear to me that is wat not that hard to create one of these things.
You have to have something to store the text you want to display and a micro controller to control every led so that it will display the text you want it to show.
I set myself a goal by using a PIC16C84 microcontroller and to see how far
we can get using this controller.
This micro controller has onboard Flash memory that will be used to store the text.
The text can be enterd using a seriel interface that connects to a RS232 port of a computer.
Display refresh timing is done using the onboard timer.
The seriel line is directly connected to the controller with a resistor.
When the contoller is not handling the display it is busy waiting for the start of the seriel communication.
The seriel communication is done on a bitbang principle and is started when the seriel line is not in idle state.
This means that when we return from an handling the display update interupt(timer) we could have missed the begining of the seriel communication.
To improve the communication the RTS line is used by the display to indicate that it is ready to receive data.
This is how it looks like in the dark.
On this foto all the circuit boards are shown. The boards are sandwiched
behind the LED boards, which are painted black.
The board closed contains the microcontroller and the first stage of te drivers for the led array.
The smaller boards contain a shift register and a driver IC.
I have made the remaining part so it is now at full length 1 meter long and 10 centimeters in heigth.
For a more detailed explaination on how it works, you can look at the design page.
|This project is not a finished product. So if u want to resuse the software or hardware ideas use it at your own risk.|