CD4026 Decade Counter With 7 Segment Display

This instructable shows you how to build a 7 segment counter using CD4026 decade counter and 7 segment decoder I.C's. Because the IC has a decade counter built into it, it is very easy to build a display with just 3 IC's and 3 displays. Watch the video to see my build on breadboard.

Here we are clocking the counter with a push button switch just for demonstration purposes but you could clock this display in any number of ways such as breaking a light beam between a laser diode and a photocell. Any clean clock pulse source will work.

The schematic diagram shows you how to connect the IC's and displays together. Note that for this test circuit we are using push buttons for clocking, resetting and disabling the display. Any clean clock pulse source can be used to increment the display and if you want you can just tie the display enable pins high permanently. This type of IC does not provide ripple blanking so the 10's and 100's displays will show a zero when not in use. Build you circuit so that the 1's display is on the right and the 100's on the left so that it is the right way around.

So the top I.C and display (1's) in the diagram is the one that goes on the right and the bottom IC and display (100's) goes on the left to create a display the right way around.

7-Segment displays used in this circuit are common cathode type displays. We can get away with connecting the IC's directly to the displays without using current limiting resistors because the IC's limit current for us as well.

If you have any trouble with noise causing the display to increment unexpectedly, try placing a couple of 0.1 uF capacitors across the power source from Vcc to Gnd.

3 - FJ5101AH 7-segment display
3 - CD4026 decade counter/7 segment decoder IC
4 - 10K resistors
3 - Push button switches
1 - 1uF capacitor
0.1uF bypass capacitors (optional)
Breadboard
Jumper wires
4.5V to 5V power source (e.g 3 AA batteries)