An on/off start-up signal governs the compressor motor of a large commercial air conditioning unit. In general, the start-up signal should be on whenever the output of a temperature sensor S exceeds a reference temperature. However, you are asked to limit the compressor start-ups to certain hours of the day and also enable service technicians to start up or shut down the compressor through a manual override. A time-of-day indicator D is available with on/off outputs, as is a manual override switch M. A separate timer T prohibits a compressor start-up within 10 min of a previous shutdown. Design a logic diagram that incorporates the state of all four devices (S, D, M, and T ) and produces the correct on/off condition for the motor start-up.
What will be an ideal response?
Analysis:
From the Karnaugh map we determine the minimum expression:
SDT + M
that is implemented by the following logic diagram.
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