External Circuit attached with PIC16F877

Discussion in 'Embedded Systems and Microcontrollers' started by ecaits, Aug 27, 2014.

  1. ecaits

    Thread Starter Member

    Jan 6, 2014
    52
    0
    Dear Friends,

    I am working on PIC16F877 project. I am using ADC and taking the signal from sensor and giving it to analog pin.
    I am preparing the circuit in which I am considering the four point given below.

    1. When sensor is short, at that time I am getting 0mV and I can declare that Sensor is fail in program.
    2. When sensor is open, at that time I will get some noise from atmosphere and I will reduce it to 0mV by resistor so that I can declare it as sensor is fail.
    3. When accidentally, I will get over voltage (any voltage > +5) at analog pin, I will reduce it to approx 5 V by using the zener diode connected to pin and ground and by sensing the +5V at pin I can declare that sensor giving over voltage.
    4.When accidentally, I will get reverse voltage (any voltage < 0 or any negative voltage) at analog pin, I will reduce it to zero voltage through zener diode and Controller will sense 0 voltage so at that case I can declare in my program that sensor is fail.

    When sensor is working normally, at that time I will get voltage 0-5V and I want to give it to analog pin without any voltage drop or minimum voltage drop.

    I have prepared a circuit, attached in file but it is not working properly.

    Please suggest me that how can I solve it.

    Thank you,
     
    Last edited: Aug 27, 2014
  2. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
    2,502
    380
    hi,
    Are you reading what helpers are posting on your other 3 threads on this same topic.?
     
  3. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,386
    1,605
    First you need to define what "not working properly" means.

    Your circuit is a voltage divider for anything less than the zener voltage. Did you account for that?

    What is this mystery sensor you frequently refer to (but never define)?

    Have you read all the other threads about your project you started?

    Mos6 PIC pins have built in ESD diodes which can typically be used as voltage limiters, but I would hesitate to advise you to use these as your sensor is still a mystery.
     
  4. ecaits

    Thread Starter Member

    Jan 6, 2014
    52
    0
    Sir,

    I am using pressure sensor...
     
  5. ecaits

    Thread Starter Member

    Jan 6, 2014
    52
    0
    Yes sir, I have worked on that but this is different issue.
     
  6. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,386
    1,605
    Gee, I wonder what a pressure sensor is.

    I also wonder what "not working properly" means.

    Finally, I wonder why simple details must be asked for multiple times.
     
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