Problem in Low Frequency

Discussion in 'Embedded Systems and Microcontrollers' started by aniket07, Feb 27, 2011.

  1. aniket07

    Thread Starter New Member

    Jan 8, 2011
    14
    0
    i am using PIC 16F877A for Peak Detection. the analog signal is applied at Pin RA0. the program has been written in C. for frequency upto 60-65 Hz, the peak is properly detected. but for frequencies below that, peak is not detected properly, instead the pin goes high well before the peak. Please help me with this problem.
     
  2. be80be

    Senior Member

    Jul 5, 2008
    431
    57
    This is what is happing your adc is taking a reading say every 10 cycles it rolled past
     
  3. aniket07

    Thread Starter New Member

    Jan 8, 2011
    14
    0
    yes, it might be true but what is happening is that it is showing high very early almost near the start of the waveform. so what can be the reason for that???
     
  4. be80be

    Senior Member

    Jul 5, 2008
    431
    57
    Last edited: Feb 27, 2011
  5. nigelwright7557

    Senior Member

    May 10, 2008
    487
    71
    Have you got weak pull ups turned on ?
    They should be off.

    Are you applying for than 5 volts to the ADC ?
    The PIC will start to play up if you go over 5 volts.
     
Loading...