Random counter circuit with 7 segment display using basic digital IC

I am going to show you a fun digital learning. Here is a random counter circuit with 7 segment display using basic digital IC.

Even though many people are interested in Arduino. Because we can use it in a variety of ways. But basic digital IC education, It’s interesting as well.

Sometimes we don’t need to use a lot of resources for small jobs. Imagine, how do you mow the lawn in the front yard? Scissors or large tractor.

So what? Basic simple circuit working.

Learn digital with 0-9 counter

They will show the random nature of the LED 7 segment. You will enjoy this project. It is suitable for digital counter learning.

When we press holding the switch. The numbers change rapidly from 0 to 9 all the time. Until the switch is released. Numbers will stop at either. Such as 5 etc.

It uses three TTL digital ICs as main components:

  • SN74LS47: BCD-TO-SEVEN-SEGMENT DECODERS/DRIVERS
  • SN74LS90 BCD Counter Circuit
  • NE555 timer.

All Parts used in this circuit are easily available in most of the local stores.

block diagram of Random counter circuit with 7 segment display using basic digital-IC

If you still do not get ideas. Let’s continue to look at the circuit.

How this circuit works

Random counter circuit

Look at the circuit above. IC1(NE555), R1, R2, and C2 are an Astable. multivibrator circuit. To generates a Square Wave signal out of pin 3 of IC1.

Related: 2 Coin toss Game circuits diagram

Then, the signal comes to pin 14 of IC2(SN74LS90). It acts as a decade counter circuit.

Next, the output of IC2 sends to the input pin of IC3(SN74LS47). The IC3 serves as a BCD to 7−Segment Decoder/Driver. To drive a 7-Segment LED display in a common anode.

It can display the numbers 0 through 9.


Test the circuit

Working start with. When pressing S1. A stable Astable multivibrator circuit products a rectangular or square Waveform. It results in a 7-Segment LED Display is a number 0 to 9.

We will see it in order from 0 to 9. And starting at 0 new again. In which it will function continuously. The speed of the display depends on the frequency of the multivibrator circuit itself. We can change its frequency by VR1.

At the same time. When pressing S1. The current charge in C1 to full, too.

After that, we released S1. The C1 discharge is current to VR1, R1, R2, C1. It causes the oscillator to run in short. We see the counter runs 7 segment display in short, as well.

Read next: IC 4017/CD4017 Datasheet | Pinout | 15 example circuits

Parts you will need

0.25W Resistors, tolerance: 5%

  • R1, R2: 3K
  • R3: 5K
  • R4-R10: 300Ω

VR1: 100K   Trimmer Potentiometer

Ceramic Capacitors

  • C2: 0.082µF  50V
  • C3: 0.01µF  50V 

Electrolytic Capacitors

C1: 47µF  25V

Semiconductors and others

  • IC1: NE555, Standard Timer Single 8-Pin Plastic Dip
  • IC2: SN74LS90, Decade counter
  • IC3: SN74LS47, BCD to 7−Segment Decoder/Driver
  • 7-Segment LED, common anode
  • S1: Normally OPEN Pushbutton switch
  • 5V Power supply

Check out these related circuits, too:

CR: photo by SenMod

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