jumbo displays

Although this project will not be of interest to everybody, it has many possible applications. The name refers to the respectable dimensions of the seven-segment displays: 280x140 mm. These sizes immedi- ately indicate that the displays are intended to make alphanumeric infor- mation legible at a distance. This is of import, for instance, for score boards, speed indicators, lap counters, digital church clocks, etc. These displays have a number of advantages: • they are entirely solid state, which prevents segment failure since the life of LEDs is much longer than, for instance, that of incandescent lamps; dissipation low. It may be said that the large number of LEDs required is a disadvantage, but, in our opinion, this is largely negated by the advantages. The seven-segment display, shown in figure la, is based on a type 74LS248 decoder, which has the same features as the well-known type 74LS47/247, but has in addition internal pull-up resistors and inverted output signals, so t...