PRACTICE PROBLEM SOLUTIONS

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5. a) If a NC stop button is damaged, the machine will act as if the stop button was pushed and shut down safely. If a NO start button is damaged the machine will not be able to start.)

b) For the actual estop which is NC, when all is ok the power to the input is on, when there is a problem the power to the input is off. In the ladder logic an input that is on (indicating all is ok) will allow the rung to turn on the motor, otherwise an input that is off (indicating a stop) will break the rung and cut the power.)

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10. C

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