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pic16f722a clarification

Discussion in 'Microcontrollers, Programming and IoT' started by PRIYADHARSHINI, Mar 22, 2015.

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  1. PRIYADHARSHINI

    PRIYADHARSHINI

    137
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    Feb 6, 2014
    Hi all
    I have used PIC16F722A for my project.It has LDO .To stabilise this LDO we have to connect sensing 0.1 to 0.01uF capacitor at RA0 and RA5 and RA6..
    is it compelsary one?
    i Don t want to use that one..if so do i need to connect sensing capacitor at the coressponding pins?
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    11,417
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    Nov 17, 2011
    Here's the answer from the datasheet:
    And on page 6 it states:
    which means you can use any of the three pins, you don't have to use all three pins.
     
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  3. PRIYADHARSHINI

    PRIYADHARSHINI

    137
    8
    Feb 6, 2014
    but may i use these three pins as a I/O ports without connecting external capacitor?
     
  4. Harald Kapp

    Harald Kapp Moderator Moderator

    11,417
    2,619
    Nov 17, 2011
    No!
    As stated by the datasheet you will need 1 (in words "one") external capacitor to stabilize the voltage from the LDO.
    If you want to use all three pins as ports, you will have to supply an external LDO (with capacitors, of course) as also staed in the datasheet.
     
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  5. PRIYADHARSHINI

    PRIYADHARSHINI

    137
    8
    Feb 6, 2014
    K. I have connected 0.01uF at RA0 to stabilise the LDO and I used the same pin as Analogue input port ( I mentioned as Resistance input)
     

    Attached Files:

  6. BobK

    BobK

    7,682
    1,688
    Jan 5, 2010
    You cannot use the pin used for Vcap for anything else. It will have a fixed voltage of 3.2V on it.

    Also, 0.01uF is not between 0.1uF and 1uF, the range needed for Vcap.

    Bob
     
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  7. PRIYADHARSHINI

    PRIYADHARSHINI

    137
    8
    Feb 6, 2014
    k.Thanks for your reply.
    this is my first project using controller.
    I have lot of confusion to draw schematic using controller.
    I have read the datasheet and draw the connections what i understood.
    Here I have attached my file ..
    Can u please guide me what mistakes have i done?
     

    Attached Files:

  8. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    Your common anode drivers wil not work well. You'd have to supply >5V to the base of the transistor to open it.
    Better use a PNP and drive it with a low signal at the base.
     
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  9. PRIYADHARSHINI

    PRIYADHARSHINI

    137
    8
    Feb 6, 2014
    how is it possible..if the voltage at the pin RB0 and RB1 will provide 5V the transistor will drive the display know?
     
  10. Harald Kapp

    Harald Kapp Moderator Moderator

    11,417
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    Nov 17, 2011
    You need to invert the drive signal. Instead of setting the port pin=1, set port pin=0.
     
  11. PRIYADHARSHINI

    PRIYADHARSHINI

    137
    8
    Feb 6, 2014
    k...but how do u say that it should have > 5v to drive the base..Sorry for my poor knowledge.
     
  12. Harald Kapp

    Harald Kapp Moderator Moderator

    11,417
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    Nov 17, 2011
    That is when you use an NPN, as in your schematic.
    A PNP can be driven by a low signal:
    [​IMG]
     

    Attached Files:

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  13. PRIYADHARSHINI

    PRIYADHARSHINI

    137
    8
    Feb 6, 2014
    thank you.i will change that one...have i assigned the connections correctly as per the pin functionality given in data sheet?
     
  14. Harald Kapp

    Harald Kapp Moderator Moderator

    11,417
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    Nov 17, 2011
    I'm not familiar with PICs and I don't have time to study the datasheet, sorry.
     
  15. PRIYADHARSHINI

    PRIYADHARSHINI

    137
    8
    Feb 6, 2014
    k.Thanks for your reply
     
  16. Harald Kapp

    Harald Kapp Moderator Moderator

    11,417
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    Nov 17, 2011
    One more issue:
    You labeled both outputs from Q1 and Q2 "COM ANODE". This will create a short circuit on the PCB as signals havin the same name are electrically connected. You need to use different names, e.g. "COM_A_1" and "COM_A_2" and also for teh displays DS1 and DS2.
     
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  17. PRIYADHARSHINI

    PRIYADHARSHINI

    137
    8
    Feb 6, 2014
    oh!...its my careless mistake....thank u...
     
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