North Park Secondary School

Computer Engineering 11 (ICE 3M0)

Experiment 12

Digital Lab 12

Binary Addition - half adder

Teacher's Name

Student's Name

Student No.


To investigate a circuit which simulates addition of 2 binary digits.


One SK-50 breadboarding socket
One 7486 TTL integrated circuit
One 7408 TTL integrated circuit
Two 470 OHM resistors
Two LED's
Seven Wires
One 9V Battery



  1. Assemble the circuit on the breadboard. (Note pins 1 and 2 are at 5 volts when they are not connected)(Note: In the schematic above if 2 wires are crossed but don't have a large dot, then the wires are not connected. BUT if the wires do have a large dot at the intersection then that means they have to be connected on the breadboard!)
  2. Observe LED 1 and LED 2 for steps (3) to (6)
  3. Connect input A and B to be both high
  4. Connect A as high and B as low
  5. Connect A as low and B as high
  6. Connect both A and B as low


Output 1 Output 2
Input A Input B Output Output
High High
High Low
Low High
Low Low


  1. Review the results in chart form of the four cases for adding 2 binary digits.
  2. Compare question 1 with the observations in this experiment.
  3. When 2 digits are added a sum and a carry are obtained. For example 1 + 0 has a sum of 1 and a carry of 0. How should the LED outputs in this experiment be interpreted?
  4. When any 2 numbers with more than 1 digit per number are added, the addition at any place value requires the addition of 2 digit per number are added, the addition at any place value requires the addition of 2 digits from the present place value plus the carry from the previous place value. For example:

    Our Circuit will simulate case A. Describe a circuit to simulate case B.


Summarize the circuit requirements to add 2 binary digits.

Page Lasted Updated 1:12 PM 9/20/2003



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