Specialized Switching for a Counter

Discussion in 'The Projects Forum' started by Bill B, Nov 29, 2009.

  1. Bill B

    Thread Starter Active Member

    Nov 29, 2009
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    I'm working on a personal project that will count the number of people entering a room. The circuitry for this is fairly simple, but the problem I am facing involves people being counted when they leave the room. The plan is to use infrared sensors to detect a person passing through the door. What I need is for the counter to increment once every two times the sensor triggers the circuit. I have considered latches, flip-flops, counters,and a mux but cannot find any way to accomplish what I need. Have I missed something or is there something I have not considered?
     
  2. Audioguru

    New Member

    Dec 20, 2007
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    What will your detector do when somebody enters and another person leaves at the same time?

    What about people who are side-by-side?

    What about skinny or very fat people?

    What about very short and very tall people?
     
  3. Bill B

    Thread Starter Active Member

    Nov 29, 2009
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    The doorway is not wide enough for two people to fit thru at the same time. A person's body will break the beam as they walk thru the doorway so their general body type won't matter. The accuracy of the count doesn't need to be exact anyway. I am trying to make it as close as possible. I could just set it up and divide the total by 2 at the end of the day but I want something more sophisticated.
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    Well, you really need two sensors; one more towards the inside of the room, one more towards the outside.

    If the sensor on the outside gets activated first, the counter needs to increment by 1 when the inside sensor gets activated.

    If the sensor on the inside gets activated first, the counter needs to decrement by 1 when the sensor on the outside gets activated.
     
  5. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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  6. Bill B

    Thread Starter Active Member

    Nov 29, 2009
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    Thanx a ton. I had considered using two sensors but I had no idea they made ICs for this application.
     
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