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ENGINEERING, TE 2023 HSC 24d

One of several fail-safe systems incorporated into a roller coaster design uses the following safety protocol.

Before a roller coaster car brake can be released to allow the roller coaster to commence its ride, ALL of the following conditions must be met:

    • passenger safety harnesses must be secured into place
    • the sensors must indicate the track is clear of obstructions
    • the ride entry and exit gates are locked.

   A logic gate schematic is shown.

  1. What is the purpose of the NAND gate in this schematic?   (2 marks)

  2. Complete the truth table for the logic gate schematic.   (3 marks)

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i.    NAND gate purpose:

→ Ensures that if any or all of the inputs are zero the output will result in a 1 and thus turn on the warning light.

→ In effect, the warning light will remain ON until all conditions for safe operation are met.

ii.    

Show Worked Solution

i.     NAND gate purpose:

→ Ensures that if any or all of the inputs are zero the output will result in a 1 and thus turn on the warning light.

→ In effect, the warning light will remain ON until all conditions for safe operation are met.

ii.    

ENGINEERING, TE 2018 HSC 21d

Digital logic controls a self-driving vehicle's brakes.
 

Brakes will be applied when all of the following conditions are met:

    • the motor is on
    • the vehicle is in motion
    • either sensor 1 or sensor 2 is activated.

Explain how the logic gates, labelled 1, 2 and 3 in the circuit below, control the vehicle's brakes.   (3 marks)
 

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  1. Logic gate 1 – AND – both inputs must be ON for ON output
  2. Logic gate 2 – OR – either input ON to produce ON output
  3. Logic gate 3 – AND – both inputs must be ON for ON output (ie brakes are applied)
Show Worked Solution
  1. Logic gate 1 – AND – both inputs must be ON for ON output
  2. Logic gate 2 – OR – either input ON to produce ON output
  3. Logic gate 3 – AND – both inputs must be ON for ON output (ie brakes are applied)