Using the 74xx47 BCD to Seven-segment display
The 74xx47 chip is used to drive 7 segment display. You must use the 74xx47 with a common anode 7-segment display (e.g. Kingbright part number SA03).
The input to the 74xx47 is a binary number DCBA where D is 8s, C is 4s, B is 2s and A is 1s. The inputs DCBA often come from a binary counter.
The display is only sensible if the binary number is between DCBA=0000 (0) and DCBA=1001 (9); this is called Binary Coded Decimal or BCD for short.
If the number is larger than 9 you get a strange output on the display. Try this out by moving your mouse over the truth table.
The inputs /, and are usually connected to 5v
- Connect Vcc [pin 16], [pin 3], / [pin 4] and [pin 5] to 5v.
- Connect Gnd [pin 8] to 0v.
- connect DCBA [pins 1, 2, 6 and 7] to DCBA on your counter.
- Connect [pins 9-15] to abcdefg on the common anode 7-segment display.