BCD/Decade counter using 74LS90. Circuit and explanation.

Package includes :

  • PCB
  • 74LS90
  • LED – 4
  • 1K resistor – 4
  • Push button switch

Assemble the circuit as shown in the following image.

Circuit diagram of BCD/Decade counter using 74LS90 is shown below.


Modules required

  1. Voltage regulator module
  2. Astable multivibrator module
  3. BCD/Decade counter module

Step 1 : Power the BCD Counter module from a 5V regulator as shown in the following image. Press and release the switch. Counter will increment the count in each press and release. Count will be in Binary Coded Decimal (BCD) form which can be read from LEDs.

Step 2 : Clock signals for BCD counter circuit is generated from an astable multivibrator module. BCD counter will increment the count in each clock pulse generated from the Astable multivibrator module. Speed of counting can be varied by changing the value of POT. This counter will count from 0 to 9.

Step 3 : Here, we will include some add-ons in the circuit to count from 00 to 99. Only thing to do is to put a second BCD counter module as shown in the following image.

Similarly adding a third BCD module, we could easily count from 000 to 999.

Watch the video demonstration here.

DIY board can be purchased from the following link.

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