What makes this LED display panel rather special is its age. It was commonly used in newsagents and tobacconists on their cigarette display shelves in the very early 80’s. That was when the very first home computers were first appearing. When LEDs were only really used as power indicators and in some very specialist scrolling message panels.
There were the first microcontrollers available back then (TMS 1000 and Intel 8048), but only aimed at hugely mass produced products with their development systems way out of reach of smaller manufacturers, so this controller is based on cheap and simple logic chips. Now it would be cheaper and simpler to do it with just a base PIC16 microcontroller and a ULN2803 driver.
The LED panel is a single sided board with a white side to reflect the light and the LEDs mounted sideways to bounce the light inside sections of a vacuum formed white plastic channel with each letter having its own light-box with a cut-out section on the front and an overlay with a block outline to translucent coloured letters.
Red and yellow LEDs were used because they were the only bright LED colours available at that time.
The controller has an unregulated 12V supply for the LEDs dropped to 5V via a 220 ohm resistor and zener. The chips are mainly a clock source, binary counter and shift register with some gating and buffering used to control the effects and drive the LEDs. The use of a bilateral switch for speed control is odd and the circuit also appears to be using the other switches as logic gates too.
It’s just a very odd and seemingly very reliable sign from an era where it was unusual enough to stick out as being “different”.
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