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Homework Help: Circuit Diagram for lights in a building (Sound/Light Sensor + Delay)

  1. Apr 23, 2014 #1
    1. The problem statement, all variables and given/known data
    Need to design a system where the lamp (output) turns on when sound is heard and turns off after 10 seconds of no sound, but it must also be dark (light sensor).

    2. Relevant equations

    3. The attempt at a solution
    I have put a Light Sensor (that is set to let current flow when it is dark). Then i have a sound sensor, connected to an inverter, which is connected to a delay (set to 10 seconds). These are both connected to the light (lamp) through an 'AND' gate so that both must be allowing current to flow for the light to turn on.

    When turning the light on there is a delay, (the question didn't say that having a delay at the start isn't correct, but if someone could tell me how to modify it so that that doesnt occur, it would be appreciated)
    Last edited: Apr 23, 2014
  2. jcsd
  3. Apr 23, 2014 #2


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    Gold Member

    the output of the delay and the output of the inverter should connected to an OR gate. The output of the OR gate goes into the AND gate.

    output=OR gate

    OR Gate:
    output=AND gate

    AND Gate:
    inputs=Or gate,light sensor.

    make sense?
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