ON OR OFF
Build and learn about an ‘AND’ and ‘OR’ computer logic circuit
RN: 11020701 - ELECTRICITY & MAGNETISM > SOLID STATE ELECTRONICS
SUITABLE GRADES
7 & 8
DIFFICULTY
3
TIME REQUIRED
<1 week
SUPERVISION
REQUIRED
INTRODUCTION [METHOD]
The first complex electronic appliances were all made up of various single components such as tubes, capacitors, coils and resistors and transistors. Today 'integrated circuits' may contain thousands of these single components built into a much smaller single unit that can perform a handful of operations. Such circuits can include storage of data 'flip-flops' and 'gates'. A 'logic gate' is a circuit that will allow passage of a signal under certain conditions only. The two most common computer logic gates are the 'AND' and the 'OR' gates. Use toggle switches to represent the concept of 'AND' and 'OR' computer logic gates in the following science experiment:
STUFF YOU NEED [MATERIALS]
- SMALL ELECTRONIC BREADBOARD
- INSULATED SOLID HOOK-UP WIRE
- 4x SINGLE THROW SWITCHES
- 2x LED LIGHTS
- 6-VOLT BATTERY
- SOLDERING IRON & WIRE
- WIRE CUTTERS
- ADULT HELPER
HOW TO PROCEED [PROCEDURE]
- Obtain a small piece of electronic 'breadboard', two 6 volt LED lights and four single pole / single throw switches from an electronics hobby store.
- Working with a soldering iron is dangerous! Ask your parents or an adult to help you with the soldering iron to connect all the components to the breadboard to form the two circuits as in the diagram above (the polarity of all the components in this experiment is important, make sure you connect the '+' and '-'terminals of each correctly!).
- Construct logic circuit 1 so that the two toggle switches are placed in series representing the 'AND' gate. Only if both switches in this circuit is placed in the 'on' position, the LED will light.
- Construct logic circuit 2 so that the two switches are placed in parallel. If either the 1st or 2nd switch is placed in the 'on' position, the LED will light!
- Make a chart with all the possible combinations of on/off positions and the switches with the 'AND' and 'OR' logic tables. Try each switch combination by placing the switches in various on and off positions and take note in which combinations the LED's are lit or not!
WHY IT WORKS [CONCLUSION]
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GLOSSARY [TERMS]
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