# Digital Displays

Purpose: Students will demonstrate how binary logic is used in common digital systems using a problem-solving approach.

Background: Parts of this lesson were used in a 1st-2nd grade multi-age class.

Reformatted: January 2010

## Part 1: numbers

We have all seen digital alarm clocks, microwaves, watches, etc. We know that they are made of lights that may be switched on or off. If the engineers use a 1 for on, and a 0 for off, what numbers do they use to make the display work?
 To left we see a way of listing all the lights that make up a display. To the right we can see which ones are turned on to make the number 2. Using the labels we can figure out what sequence of 1's and 0's will give us a 2.
 a b c d e f g h Light segment on off on on on off on off state 1 0 1 1 1 0 1 0 number
Therefore a 2 is displayed by the binary signal: 10111010.

[1] Is this the same or different as the binary number for 2?

[2] Now that we know how to do 2, use this idea to show how to display 1,3,4,5,6,7,8,9, and 0.

Related pages at this site

## Part 2: letters

Some times engineers have to abbreviate words with these displays. What letters can they make? What letters can they not make?

Above we can see that the letters "A" and "b" can be made using the seven segment display. Can lower case "a" be made? Can capital "B" be made? Determine what letters, both upper case and lower case, can be made. Make sure that there is no confusion between different letters (for example "a" should not exactly the same as "o".) Write the sequence of 1's and 0's that denote each letter.

### Summation:

Once you have solved this, you have solved a problem that software engineers must solve. How do you think the engineers get the sequence of 1's and 0's from the processor to the display? How do you think they translate from the numbers in memory stored as binary, and the letters in memory stored as ASCII to the sequences you generated above?