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pic 16f877a program problem

Discussion in 'Microcontrollers, Programming and IoT' started by shrinivasdevkar, Feb 22, 2014.

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  1. shrinivasdevkar

    shrinivasdevkar

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    Feb 22, 2014
    I want take value which is already displayed on 3 digit-7 segment display, that value is 3 digit , if display is common cathode and display selection pins are 12, 8, 9 then how should i write program for that in c
    display connection details are as follows
    pin no.
    1 anode E
    2 anode D
    3 anode DP
    4 anode C
    5 anode G
    6 not connected
    7 anode B
    8 common cathode digit 3
    9 common cathode digit 2
    10 anode F
    11 anode A
    12 common cathode digit 1
     
  2. BobK

    BobK

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    Jan 5, 2010
    Are you saying you want to microcontroller to read a value that is displayed on a 3 digit 7-segment display?

    Bob
     
  3. shrinivasdevkar

    shrinivasdevkar

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    Feb 22, 2014
    yes sir.... plz help me....
     
  4. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    LOL :)

    Go Bob! Go Bob! Which microcontroller are you going to use?

    shrinivasdevkar, can you answer some basic questions.

    What is driving the displays?

    What is the product? Some kind of counter?

    What supply voltages are available?

    Have you done microcontroller development before? If so, which device(s) did you use?
     
  5. shrinivasdevkar

    shrinivasdevkar

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    Feb 22, 2014
    Sir i'm using PIC16f877a controller and device which used from which the 3 digit data i have to get is temperature controller device TC303AX that was selec company product that product displaying temprature in which the thermocouple is dipped....in that device ther are some voltages are available on PCB board like 5.25V, 6.75V , 7.25V also in -ve

    and i want to take that data into pic16f877a for my project perpose..

    first i worked with controller P89v51RD2

    [Moderator's note: I've combined your three posts into one - KrisBlueNZ]
     
    Last edited by a moderator: Feb 23, 2014
  6. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    OK, that's useful information.

    It should be possible to do what you want, but there is some hardware and software work required.

    That multiple-digit LED display must be driven using multiplexing. If you don't know what that is, Google multiplexed led display drive.

    To read the contents of that display, you will need to monitor the eight outputs that drive the segments, and the three outputs that select the digits. (It's possible that the digit selection is done with a 2-bit binary control signal and a decoder, but more likely there are three separate control lines.)

    You need to find out how the display driver works, and where you can get access to those signals. Preferably they should be at 5V levels so you can feed them straight into your PIC microcontroller.

    Then you need to write code in the PIC to detect when each digit is enabled, read the segment enable signals, decode them into a digit, then combine the three digits into a number that can be used for whatever you want to use it for.

    Assuming you can get access to all of the signals at logic levels (so you can connect them directly to the PIC inputs), you could build a fairly small board that might fit inside the meter's case. It would need 13 connections to the meter board:

    8x segment enable signals;
    3x digit enable signals;
    VCC and 0V.

    Can you take a photo of the inside of the meter? Both sides of the board would be good. Make sure that IC markings are readable. If necessary, move the display so we can see what's behind it.

    Do you understand what I've described so far?
     
  7. shrinivasdevkar

    shrinivasdevkar

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    Feb 22, 2014
    images

    Sir i'm sending some photos regarding my problem.........in images there is temperature sensor kit and anather ckt is of quard op-amp desined because the display segment not giving 5V across it.........by using that ckt. i want to make that voltage as logic high and apply to pic to read the k-type thermocouple reading......
     

    Attached Files:

  8. shrinivasdevkar

    shrinivasdevkar

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    Feb 22, 2014
    in 3rd image the k-type thermocouple ,and in 1st 5 images are of that device TC303AX temp. controller.....and last two photos are of ckt desined for testing voltage at o/p of LM324
     
  9. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    When you measure voltage across segments in the display, you will not see 5V for several reasons. First, the forward voltage of a single red LED is around 2V (if the segment is powered from 5V, the remaining 3V is dropped across the current limiting resistor). Second, each digit is only enabled for 1/3 of the time.

    You should not measure the voltage across the segments. This will not give a useful result, because of the multiplexing. Do you understand multiplexing?

    The device (probably a microcontroller) that drives the 3-digit display will have a number of output signals that are probably all logic-level signals. You can connect these directly to your PIC. You should not need any op-amps or comparators. You just need to figure out where all the signals are.

    I need to see both sides of all of the circuit boards inside the TC303AX. They need to be in focus, and all the component markings need to be readable.
     
  10. shrinivasdevkar

    shrinivasdevkar

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    Feb 22, 2014
    Sir can i connect the segment connection that can be seen in photo 2nd (12 leads of display) as you give in reply 6....but what about ground because without ground there is no voltage development....
     
  11. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    It will be simpler to connect to the logic-level signals (0V/5V) which drive the anodes and cathodes of the display. If you do that, you won't need any op-amps or comparators. Yes you will need to connect the 0V rail of the TC303AX to the 0V rail of your PIC circuit. You may also be able to use the TC303AX's +5V power supply for the PIC.

    Do you understand multiplexing?
     
  12. shrinivasdevkar

    shrinivasdevkar

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    Feb 22, 2014
    Sir also in that case help me in case of program how to write in C .....plz
     
  13. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    OK, I will help with the program once you have worked out where to get the segment and digit control signals on the boards inside the TC303AX and drawn up a schematic diagram of your PIC circuit.

    Do you know where to get those signals? If not, I will help you find out. I need to see both sides of all of the circuit boards inside the TC303AX. They need to be in focus, and all the component markings need to be readable.

    Do you understand multiplexing?
     
  14. shrinivasdevkar

    shrinivasdevkar

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    Feb 22, 2014
    please give me some such kind of program....
     
  15. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    I don't have one.

    Are you asking me to write your code for you?

    Post photos of both sides of all of the circuit boards inside the TC303AX. They need to be in focus, and all the component markings need to be readable.

    Do you understand multiplexing?
     
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