Circuit to Interface a 4*4 Button Pad to Arduino using 4 Digital Pins (Part 1 of 3)

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We had already seen the circuit for interfacing a sealed membrane 4*4 button pad to arduino mega in one of my previous blog. Main disadvantage of that circuit is it’s necessity of eight digital pins of arduino to control a 4*4 button pad. If you are using arduino uno or such small boards, only 6 digital pins will be remaining (out of 14 digital pins) after connecting the 4*4 button pad to arduino uno. Remaining 6 digital pins will not be enough for some big applications. Then, we have to go for a technique which will reduce the number of digital pins needed to interface 4*4 button pad to arduino. Here, we will see a technique in which only four digital pins of arduino is enough for controlling a 4*4 button pad. Circuit is done as shown in the following diagram. If the circuit is not clear, view it on pinterest for a larger and clear view.

Before starting the circuit, you must read tutorials on :

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Circuit is done as shown in the diagram. If the circuit is not clear, view it on pinterest for a larger and clear view.

Connection between arduino uno and 74HC595 can be summarized as :

  • Digital pin 13 of arduino uno is connected to pin 11 of 74HC595.
  • Digital pin 12 of arduino uno is connected to pin 12 of 74HC595.
  • Digital pin 11 of arduino uno is connected to pin 14 of 74HC595.

Connection between 74HC595 and 4*4 button pad can be summarized as :

  • Pin 15 of 74HC595 is connected to the K terminal of 4*4 button pad.
  • Pin 1 of 74HC595 is connected to the L terminal of 4*4 button pad.
  • Pin 2 of 74HC595 is connected to the M terminal of 4*4 button pad.
  • Pin 3 of 74HC595 is connected to the N terminal of 4*4 button pad.

Connection between 74HC165 and 4*4 button pad can be summarized as :

  • Pin 11 of 74HC165 is connected to the O terminal of 4*4 button pad.
  • Pin 12 of 74HC165 is connected to the P terminal of 4*4 button pad.
  • Pin 13 of 74HC165 is connected to the Q terminal of 4*4 button pad.
  • Pin 14 of 74HC165 is connected to the R terminal of 4*4 button pad.

Connection between 74HC165 and 74HC595 can be summarized as :

  • Pin 15 of 74HC165 is connected to the pin 4 of 74HC595.
  • Pin 2 of 74HC165 is connected to the pin 5 of 74HC595.
  • Pin 1 of 74HC165 is connected to the pin 6 of 74HC595.

Connection between arduino uno and 74HC165 can be summarized as :

  • Pin 9 of 74HC165 is connected to digital pin 10 of arduino uno.

Other connections :

  • Pin 10 and 16 of 74HC595 should be connected to 5V.
  • Pin 8 and 13 of 74HC595 should be connected to ground.
  • Pin 16 of 74HC165 should be connected to 5V.
  • Pin 8 and 10 of 74HC165 should be connected to ground.
  • All terminals of 4*4 button pad should be connected to the 5V pin of arduino uno through individual pull up resistors of 1K each.
  • Ground terminal of external power supply should be connected to the ground terminal of arduino uno.

Continued in Next Part (Part 2) >>>>

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paulpp644
A deep electronic enthusiast who spent most of my time for electronic experiments. I am also interested in publishing my experiments in my blog for helping other electronics enthusiasts.