DIY Event Counter/Clock using 555 Timer and CD4026B

Note: This is a instructional DIY project with little or no theory included.

Complete Project look! Don't worry, you'll reach here.

Ever wanted to make yourself a clock that can change its speed by making a little adjustment on a resistor attached to a 555 timer. This is known as an event counter that counts the changes in event in the applied square wave.

😉 Funny coincidence: The moment picture of project was taken, 88 got captured at exactly 8.8 V.

As the 555 timer accounts to any change in event, a counter increases the count by one. 4017 is the decade counter that does this counting. The internal circuitry of 4017 is actually really simple to understand. Five D flip-flops are arranged in a way that the output in each stage appears to be in a ring. This gives this circuitry its name: Ring Counter.

Number of stages in a Johnson Ring Counter is given by:

2 times the number of flip-flops present

The truth table for the output of 5-bit Johnson Ring Counter is shown below:

Output of 5-bit Johnson ring Counter

To generate a square wave of variable frequency, you will have to use 555 timer in Astable mode. The circuit for 555 timer in Astable mode is shown below:

Schematic - 555 Timer in Astable Mode

Now by looking at the timing diagram of 4017 output:

Timing Diagram of 4017 taken from datasheet

It is clear that the counter is working just the way we wanted it to work. But considering to make a clock and using 7 segment display to use as the output, you need to somehow transform each stage into a 7 segment data. For that, you will need to first convert each stage to BCD data and then convert it to 7 segment data using 7447 or 7448 chip. This will require some digital logic circuit designing, a long shot that is!

A simpler way to solve this problem is to use all in one packaged CD4026B which is a Johnson Ring Counter with output generated specifically for 7 segment displays. Take a look at the timing diagram of 4026 chip:

Timing Diagram of 4026 taken from datasheet

We have designed the whole schematic for you which includes 555 timer based frequency generator and a 2 digit counter using two 4026 chips:

Complete schematic of an Event Counter

Rendered look of this project

Download the files below as they are likely more accurate and updated.

Downloads:

Schematic - Circuit

PCB design - Bottom Copper and Top Silk

Don't wait, grab the components and make this circuit. If you need any theory on this project, just comment down below or you can always contact us without any hesitation. ✌

Zain Ul Mustafa

Cakes, conspiracies, and computers are my daily pills.

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