Led Writing Board With Digital Computer
Based on the above discussion on the digital computer LED writing board of the present invention, the fine electrode lines by groups of high, low soft piezoelectric film are disposed perpendicularly to each other to combine insulation film, resilient pad and protective film in performing the scanning and detection by groups within scanning, detection circuits to form a computer LED writing board of high resolution, in which a common writing instrument can be used to write or draw directly, while the character tracig and groups signal can be read in their original form and to achieve a goal of having all written or drawn stored in a memory, or displayed on a screen, or printed out accurately with their fidelity. The present invention of computer LED writing board has a complete new and inventive design with highly practical value.
The advantages of the frame of coding scanning by groups used in the digital computer LED writing board will greatly reduce the number of input terminals of both comparator and multiplexer. For example, each column or row has 256 fine electrode lines which are divided into 16 high groups and 16 low groups, for which the scanners require only 32 input terminals for comparators and multiplexers (16 input terminals for high groups and 16 input terminals for low groups). A common non-coded scanning technique requires 256 input terminals for both the comparators and multiplexers. It can be seen from this that the scanning by coding as used in the present invention has been capable of very effectively reducing the circuit complexity and greatly reducing the cost.
In the column, row scanning and detection circuit of digital computer LED writing board, a subgroup coding scanning frame is used, with its operating principles and the wiring shown in FIGS. 11 and 12. The sub-group electrode lines on PVDF piezoelectric film are divided into several high groups while the frequency of scanning clock (approx. 4 MHz) is divided by a binary counter, also divided into high and low groups for pushing the multiplexer of high group (collective group I to 1 multiplexer on FIG. 12) and low group (dispersed group J to 1 multiplexer on FIG. 12) to scan fine electrode line group.
