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Thinking logically

Open a gateway to the world of analogue and digital, as we recreate different electronic circuits to see how they work.
Plan a session with this activity

You will need

  • Pens or pencils
  • Scrap paper
  • Lengths of rope
Logic gates explained
PDF – 280.9KB

Before you begin

  • Make sure there are pens or pencils and some paper available, for those who prefer to write things down.

Run the activity

  1. Explain the difference between analogue electronics and digital electronics. If in doubt, use these definitions:
  1. Give out the copies of the ‘Logic gates guide’. There should be one between two or three. The gates work just like garden gates, opening to let you into your garden, but staying closed to keep intruders out. Point out that the simplest ‘gates’ have names that describe what they do: ‘AND,’ ‘OR’ and ‘NOT.’
  1. Explain what AND, OR and NOT gates do. If in doubt, use these definitions:
  1. Explain that logic gates are made up of transistors, resistors, diodes and, at the centre, a microchip. They’re the basis for all modern computers. Here are some examples you can share of AND and OR gates in practice:
  1. Have everyone make logic gates of their own. Everyone should split into groups of three and pick a number: one, two or three.
  2. Give each group a length of rope. Number One should hold the middle of the rope, while Number Two and Three should hold the ends, making a triangle shape.
  3. Explain that for this game, Number Two and Three are inputs, while Number One is the output. Number One should come up with an output signal that they’ll do when the gate opens. For example, they could raise their hand or blow a raspberry.
  4. Start with an AND gate. Both inputs need to send a signal for there to be an output. Number Twos and Number Threes should both tug the rope at the same time if they wish to open the gate. If only one of them or neither of them tugs, the gate shouldn’t open
  5. Now, try an OR gate. Either input can send a signal and produce an output. Either Number Twos or Number Threes can tug their end of the rope and the gate should open. If neither of them tugs, the gate shouldn’t open.
  6. Give out copies of the attached diagram. Try forming some of the larger sets of gates from the diagram. Stick with OR gates for now, so that all inputs have an output.
  7. The output for everyone apart from Number One, Seven and 11 should be to pull the rope and send the signal on to the next gate. If anyone’s holding more than one rope, they should pull both at the same time. Start by trying to activate Number One, but not Seven or 11.
  1.  Introduce AND gates to help the group activate the output they want. The AND gates need to be placed in areas where both inputs have to be turned on to get the output. You may need to move the AND gates around to activate different people in the group.
  1.  Gather everyone together again and go back to the difference between digital and analogue electronics. Explain the difference between variable (analogue) and finite (digital) signals. You could use the examples below:
  1.  Share some more facts about why we use digital circuits:

Reflection

It’s a small step from digital circuits to the world of computer programming. Why do you think computers need digital circuits to work? Why couldn’t they have worked with analogue circuits? Some reasons might be the stability of digital circuits, their reliability, their size and the way they work.

Working out the routes of signals needed you to think carefully and plan ahead. Where else might this skill be useful? Imagine you’re planning a hike or baking a cake.

Safety

Active games

The game area should be free of hazards. Explain the rules of the game clearly and have a clear way to communicate that the game must stop when needed.

Electronics

Remove any equipment you’re working on from the power source before you begin. Never assume the power circuit’s off – test it with a voltmeter (and then test it again to be sure).

Only connect power to a circuit once you’ve finished working on it and have checked your work. Make sure your circuit isn’t overloaded, and return any covers you’ve removed.

Make sure that all electronics equipment is properly grounded. Use the right electronics tools, and always replace damaged equipment (for example, replace cables rather than repairing them with insulating tape). Always have safety equipment including a fire extinguisher, basic first aid kit, and mobile phone nearby.