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Help with safety circuit

Discussion in 'Homework Help' started by makel, Feb 17, 2016.

  1. makel

    makel New Member

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    Studying Mech Engineering and one module is on Electronics. The lecturer broke his hip second week of the course so we have not been taught. I need to design a circuit and truth table and I am struggling to do so. I will post question and what I have done so far.

    A powered guillotine uses a motor to position the cutter. The cutter must not operate while the motor is running. There is a guard which must be closed and locked before the cutter can operate but there is a maintenance facility which will allow the cutter to operate with the motor stopped but the guard open. A traffic light system must be incorporated to show when the Guillotine is unsafe (red), safe (green) and when in maintenance mode (amber). The guillotine can only operate once when in maintenance mode.

    Draw the Karnaugh map and design the safety circuit using two input NOR gates (use as many as you require).

    If each gate has a MTTF 1526173, calculate the MTBF for your circuit (in hours).

    How could you redesign the circuit for an improved MTBF?

    How could you achieve a MTBF of 1 × 109 hours?

    What will the reliability be after 5 years?

    I have made a truth table but I dont know how to incorporate the cutter only working once in maintenance mode. I think I need to use an RS Flip Flop but I dont know how I can implement this into my table and circuit. I made a circuit from my table using AND gates and I need to convert it to NOR. I tried to do so but it effected the truth table and I dont think my inputs were right as I needed 3 NOR gates for 1 AND gate. For the redesign I know I need to simplify the circuit and reduce the NOR gate number. Any help is appreciated
     
  2. Dr_Doggy

    Dr_Doggy Well-Known Member

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    hmm, my guess is.....

    a & b = !(!(a+b) + !(a+b)) .... that is equation to convert and gate to nor gate, so by substituting all (A * B) with !(!(a+b) + !(a+b)) in your equation , your map should not be impacted, although that is the limit of my help, others may be able to help more if you post truth table and equation generated from it...
     

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