How to Build an LED Display Counter

Written by david gitonga
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How to Build an LED Display Counter
An LED display counter uses a simple circuit to display information. (load image by pickks from

A display counter can be constructed quickly. Since all the materials are readily available, the work involves simply assembling the parts, soldering the parts on a board and ensuring the proper amount of voltage is applied to the appropriate pins. In order to build such a digital device, it is advisable to become familiar with the circuit behind it. These circuits are contained in integrated chips.

Skill level:
Moderately Challenging

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Things you need

  • 4511 BCD-to-7 segment decoder driver (IC)
  • Common cathode 7-segment LED display
  • Prototype board
  • DIP switch (8-position)
  • Seven 470 ohms resistors
  • Four 10 ohm resistors
  • Battery, 6-volt

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  1. 1

    Lay out all the components on the prototype board as shown on the schematic and the illustrated diagram in the link below. (See References 1)

  2. 2

    Solder each wire as shown in the schematic.

  3. 3

    Apply the appropriate voltage (5V) to the circuit as shown in the illustration. The display should light up, indicating that it is ready for operation.

  4. 4

    Use the DIP switch to operate the circuit. To have a counting sequence, start by inputting a 0000 to have the number "0" displayed. To have the number "1" displayed, input a 0001. Use a similar approach to display the other numbers in the sequence.

  5. 5

    Use the manufacturer's datasheet for the 4511 IC to operate and display using different approaches. For example, the input switches can be connected differently to allow the user to alter the BCD code of the four switches.

Tips and warnings

  • When laying the circuit, ensure that all the common points are aligned on one side, either on the cathode or anode. This makes it easy to locate common points like the ground and to add more components, like extra displays, should the need arise, or to change the existing one if it is faulty.
  • Some ICs, like the ICM7244, act as LED display decoder drivers and controllers and come with all the circuitry inside to interface with a 16-segment display. They minimise the hardware and software overhead needed when designing a complicated display unit.
  • Since the 4511 is a CMOS IC, it should be handled with care to prevent damage from static electricity. Follow static electricity precautions when handling this IC. (See References)
  • Always use the recommended value of the resistors. These resistors are used to sink excess current in the form of heat. These resistors may get hot. However, this behaviour is quite normal during operation.

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