A 7-Segment display is made up of seven rectangular LEDs arranged in a figure of
8 pattern. By lighting up the LEDs in the right order it is possible to get them
to display the numbers 0 to 9.
An integrated circuit (IC) is available called a 4026 which allows you to build a
counter that will increase its value every time it receives a clock pulse. This pulse
could come from a switch of some kind or the output of an other circuit, like an
astable circuit for example.
What the inputs and outputs do
CE = Chip Enable
This must be connected to 0V to turn the 4026 on.
DE = Device Enable
This must be connected to +V to turn the 4026 on.
EO = Enable Output
This must be connected to +V to turn on the LED display.
R = Reset
When this input has a logic 1 connected the display will be reset to 0.
> = Clock Input
Each time a logic pulse is received by this input the display will increase its value
a, b, c, d, e, f, g = LED outputs
Each LED segment is connected up to the each of these outputs. The 220R resistors
must be included to limit the current flowing through the LEDs, this prevents them
from becoming damaged.
Although it isn’t shown in the diagram the 4026 chip also has 0V and +V inputs.