Paolo Koussis

Salvatore Damino

KAD-08 - Alphanumeric LED display.


We have already learned the technique to correctly manage a 7 segments numeric display and now we can undertake the management of an alphanumeric display. In detail, we'll try to drive a14 segments display, commonly named "English flag" because they recall the characteristic Union Jack design of the English flag. The little board is the KAD-08 where 8 alphanumeric displays plus 4 segnalation LEDs are mounted.



The driving circuit of KAD-08 is well known and it is based on the M5451 comfortable use.
This component is really similar to M5480 that has been examined in the last issue (E.F. n° 199 - November 2000) and it includes all the driving circuits for a maximum of 35 segments LEDs.
The driving is still based on a constant current generator.
The M5451 has a 40 pins package to obtain the sufficient space for all the required outputs.
Taking advantage from the multiplexing tecnique, the M5451 can drive up to 124 LEDs by using only its 35 outputs.
Also the circuit is really similar to those previously described for the numeric displays.



The refresh technique usd by this card is analogous to the previously dscribed one. You can see that the data stream, during the serialization phase, is different but this is a consequence of the different structure of the component's internal registers that however mantain the same functionality.
Even if the electric diagram has no difficulty I suggest to carefully read the SGS-THOMSON data sheets in fact they explain both hardware doubts and firmware management drivers.
From a practical point of view it is always suggested the use of a card, i.e. GPC F2, to experiment the program potentiality.

fig. 3 - KAD-08 - card Diagram.


R1÷ R7 = 4,7k - 1/4w
C1 = 22µF/6V tant.
C2 = 1nF/50V poli.
C3 = C4 = 100nF multist.
LD1÷LD4 = Red LED 3 mm
DY1÷DY4 = PDA54-11, 15 segment*2 display
IC1 = M5451
IC2 = ULN2074
CN1 = 4 screw terminal; 2,54 mm
40 pin Socket
16 pin Socket



The program that manages the data visualization follows the same logic of the numeric displays but it is more complex. The increased difficulty is basically caused by the necessity to show the characters; so a complete table with the full ASCII codes has been created and through this table almost all the typical symbols can be displayed. Naturally the table can be changed as You like and You can create any simbol supported by the 15 segments tecnique.



Through this card You can build notice boards with sliding messages of the required dimension, by simply placing side by side the proper number of KAD-08 cards. You can use it to realize bright visualizations or, if the electric diagram is suitably modified, You can develop many new applications restricted only by Your fervid imagination.


Data Sheets:


Page up-dated at August 29, 2004

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