Introduction: Understanding 74LS273 Octal D Flip-Flop IC

I got my hands on 74LS273 IC while I was salvaging some components from an old satellite receiver, something I do between projects and save some money….

This IC was on the control panel and was wired to 4-Digits 7-Segments LED display with some transistors. This made me interested to see how it works. I never used one before and therefore I had no idea how to wire it in order to make good use of it.

I made few internet searches but couldn’t find any wiring diagram or sample circuit that would help me out. There are many datasheets and pinout readily available…. that was useful and a good start for me.

Step 1: Part List:

In order to have a good understanding of how the 74LS273 functions, I had decided to build a simple circuit with visual presentation for the output; a sequence of numbers is always a good idea therefore I decided on 1-Digit 7-Segmnet LED Display, and instead of running it manually, I decided to automate the process somewhat by using a microcontroller (Arduino). The following are the components needed:

Parts List:

  • 74LS273 Octal D Flip-Flop IC
  • Arduino NANO
  • 1-Digit 7-Segment LED Common Cathode Display
  • 8x 200 Ohm Resistors (value depends on the 7-Seg. LED Display)
  • Breadboard
  • Hook-up Wires
  • 5 VDC Power Source

Step 2: 74LS273 Pinout:

Before building the circuit, let us have some understanding of the process which I am about to have the Arduino to follow:

  • The 74LS273 IC has 8 data input pins and 8 latching Flip-Flop output pins, also it has 2 inputs pins for Clear and Clock.
  • In order to display a digit you could follow these steps:

o Set all data pins to LOW

o Set Clear pin to LOW then set it to HIGH

o Set required data pins to HIGH; these pins correspond to the digit you need to display

o Set Clock pin to LOW then set it to HIGH

Step 3: Here Is the Hardware Hock-up Diagram:


I ran into some difficulty therefore I tried 10K pull-down resistor on Arduino pin-11 and 10K pull-up resistor on Arduino pin-10, this solved the problem. But I had removed them afterward once I got the circuit working well. The resistors helped me during testing, but they are not necessary afterward.


Step 4: Arduino Code:

Step 5: Video:

Enjoy.... Hope this was useful.....