LED signage has become the choice in modern days to convey message to visitors of a venue. Be it corporate office, shops, restaurants or any kind of social functions like marriages. Some big and complicated display needs dedicated control PCs and designers to build contents for them. But for simple requirements a very low cost AVR microcontroller based PCB is enough. This kind of display shows a message that scrolls from left to right on a LED display screen. To make it easy to use they don’t need any PC to program message to it. A PS2 keyboard can be attached and message can be typed. Message is stored in the internal EEPROM of the AVR and thus does not get erased even after the system is switched off.
In this article we will discuss design of such a control board that can drive four P10 displays which has a combined resolution of 128×16 pixels and 4 feet length. Height is 6 inches. This is perfect for most outdoor display requirements. We have chosen AVR ATmegs8 which is a 28 PIN microcontroller IC. This IC is low cost and is available at under 90 rupees (US$1.50) Thus the control board is very low cost and small in size.
Circuit design for moving message display is very simple. At the heart we have put the ATmega8 microcontroller, which is connected to a 2×8 female header that can be plugged directly to the 2×8 male headers for P10 display. Since P10 displays are cascadable, and has a output terminal too, this terminal can be used to connect next display. In the same way one more panel can be connected. So a total of four P10 panels are cascaded.
One more thing that is connected to the ATmega8 is a PS2 connector where we can hookup a standard keyboard. PS2 connector only has 4 connections.
We do NOT use any voltage regulator ICs in this circuit because to power p10 displays we need a 5v 6A SMPS power supply which already regulates voltage to 5v. So we can connect this 5v directly to the ATmega8 also.
As you can see in the image above the module has a 16 pin header that is used to connect it to the controller board. The board also has a power input terminal that should be given a 5v DC input that can source upto 3A current.