Here are some modules I designed for easily mounting and controlling Kingbright's SC18-11EWA 45mm 7-segment LED displays. The LED segments have a forward voltage of around 6 volts, which makes the CD4511 BCD to 7-segment decoder / driver ideal for controlling them. This chip being part of the 4000 logic series has a wide operating voltage range, and can source 25ma on its outputs for driving the SC18-11EWA common-cathode displays directly, and without the need for current limiting resistors. These features made it possible to create a compact display module based on the following schematic.
The power and data connections are provided by the 14-pin header / IDC socket mounted on the rear, which allows full control of both displays. The A,B,C,D Binary Coded Decimal inputs for both drivers ICs are paralleled together, and an individual display can be addressed via these data inputs by setting the latch input of the corresponding driver chip.
These display boards were originally intended for use in a clock project, and so a further colon separator PCB was designed to fit between them. Each board has a set of 3.1mm mounting holes, making it easy to fix a row of PCBs to a pair of horizontal rails with M3 screws.
Driving the four segments requires only four digital outputs for assigning a value, and four additional outputs for selecting the individual display. This makes it easy to control the four digits using just a single 8-bit port of a microcontroller, 74HC595 shift register, or the 6522 Versatile Interface Adaptor as was originally intended. Obviously in the case of a clock display arrangement, one additional output and drive transistor would be required to control the colon, assuming it were to do anything other than remain static / permanently on.
I'm powering the CD4511BE drivers from a 7.5 volt supply with the digital logic on the inputs operating quite happily at the 5 volt levels supplied by the Arduino Mega 2650 I'm using in the following demonstration video. When all segments of the four displays are illuminated the total current draw is just over half an amp, so probably not ideal for battery powered applications!
Gerber files for these PCBs can be downloaded here...
cd4511_7_seg_displays_gerber.zip
cd4511_7_seg_displays_colon_gerber.zip