Matrix Projector with Dual Color LED

Figure 1 

Using dual color LED matrix, the project was designed to provide fairy visual projection on ceilings or walls.

The matrix has been organized in 8 rows and 16 columns with 8 red and 8 green LED. A single LED in the matrix can be addressed by setting one of the 16 column bits and the corresponding row is enabled. This concludes that only a single row is always active. A steady picture can be projected if every row is activated fast enough. The column data is being provided by the shift registers while the 16 bits are loaded serially and put out in parallel. The 16 bits of data has been provided at least every 2.5ms to generate a steady picture.

An array of Darlington transistors ULN2803 handles the rows and sinks the current of the activated row. If every LED is activated in a single row, the current in this row will be sum up to a value too much to handle for a single pin of a microcontroller. 500mA per channel can be lowered down by the ULN2803. The image is controlled by a script language arranged in small sequences.

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