DIGITAL DESIGN USING LOGIC.LY

TASK – SEVEN SEGMENT DISPLAY

 

 

TASK DESCRIPTION

 

A seven segment display is a small device that contains seven different LEDs organized to display all numbers from 0 to 9 (and sometimes also the letters A-F).  You have seen them in digital clocks (such as alarm clocks).

 

You will learn how this device works.

 

THEORY

 

PART 1 – SEVEN SEGMENT DISPLAY

We can manually connect the seven segment display’s LEDS to power (with resistors) to turn on and off specific LEDs and hence forming certain numbers.  The video below demonstrates this and much more.

 

View the video below from 1:45 – 3:10.  You can certain watch (and learn) more.  Note that it is hard to understand everything in a video without doing this yourself.  Do not worry if you have difficulties understanding many of the concepts.

 

 

PART 2 – THE 7447 CHIP

 

When creating a device, we need to be able to provide a 4-bit number such as 0101 and have the seven segment display show the corresponding number 5. 

 

If you watched all of the video above, you see that it can be done in a very painful way using OR gates.  However, there is a 7447 chip that is designed to convert a 4-digital binary input into the input needed by the seven segment display.  (This is what we usually do in class.)

 

The following video shows the 7447 chip in action.  Watch it to see the steps that you would have to go through to create this circuit but of course, it is hard to follow all of the details.  Do not worry about understanding everything.

 

TASK

 

In logic.ly, connect a seven segment display to four toggle switches (like below).

 

 

Notice that in the image above, you are entering the value 1001 into the 7-segment display and are getting a 9.  Of course, 1001 in binary is equivalent to 9 in decimal.

 

TO SUBMIT

 

A screen capture with the input 0111 being entered into the display. 

While you do not have to submit this, you should be able to predict what a display will show if I give you an input such a 0100.

GOT EXTRA TIME?

 

I have not tried this yet. J

 

But we can use a seven segment display and full adders to add up two 4-bit numbers and have a decimal result showing.  I will give extra credit if you achieve this but note that this will be messy and challenging.