HELP ... to make a circuit sensor that counts persons passing

Discussion in 'Homework Help' started by acastro, Nov 27, 2009.

  1. acastro

    Thread Starter New Member

    Nov 27, 2009
    Hi, im a high school portuguese student of Informatics and i have some jobs to do in order to obtain success to DIGITAL SYSTEMS.

    I have already made the other tasks, but the last one is a jigzaw that is blowing my brain apart.

    I have to make in digital works 2.0 a circuit that has 2 sensors.

    S1 - counts the number of persons that pass by him towards a stair-case rolling.

    When more than 15 persons passed by S1 , but didnt pass by the end of the rolling stair-case which has a S2 sensor, the stair-case has to stop moving. When some of the persons in excess leaves through the S2 sensor and count falls under 15, the stair continues to roll.

    I dont have a single clue on how to make this.

    Do i need to use a ADDER, or a Sinchronos counter based in flip flops, or Multiplexers, or something else, i realy JUST DONT KNOW.

    my job delivery date expires Sunday 29 ate 20h pm and i need this made to have a good grade.

    Please, someone enlight me the way...

  2. MauriceS

    New Member

    Nov 27, 2009

    A possible solution is to make a 5 or more bit up / down counter.

    S1 makes it count up, S2 makes it count down. If bit 5 is set the criteria is met (i.e. > 15)

    Problem is possibly the reset condition - if someone is on the stair while power fails it would get out of sync... so if you want to be really smart - make the count down function never go less than 0... Then it would recover.

  3. acastro

    Thread Starter New Member

    Nov 27, 2009
    Thanks for the Help Maurice,

    the problem is i dont know how to plug S1 and S2 to the inputs od the counter.

    s1 connects to ??

    s2 connects to ??

    can you make some kind of drawing with JK or D or T flip flops connected to the s1 and s2 sensors, T is my favourite one, but i dont know if it is possible to do the job with a type T.
    Maibe JK will be easier. You decide.

    i hope not to be abusing of your time or simpathy.


  4. acastro

    Thread Starter New Member

    Nov 27, 2009
    IS somewhere in this forum, somebody that can answer the question that i posted above:

    S1 connects to ?

    S2 connects to ?

    Thanks, in advance ...