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Digital Countdown Timer (AT89C2051)

Discussion in 'Doubts in My Projects' started by Binu, Jun 7, 2007.

  1. Binu

    Binu Administrator

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    A simple count-down LED timer that counts in minutes and seconds. Three buttons below the LED provide control of the unit, allowing you set the desired countdown time in minutes and seconds and a start/stop button.
    Completion of the countdown is indicated by an alarm that starts when the countdown has finished and the display reads zero.
    The alarm is stopped by pressing the start/stop button.
    Program: View attachment count.zip
  2. Arun Kumar V

    Arun Kumar V Member

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    Hi Binu

    In the program you have defined the RESET Button and also shown in the Diagram, but no where you are Checking for its BIT condition, nor there is a Interupt Service Routine for this Button,

    Secondly, there is no provision for the user to enter the Desired time for countdown ( Plus & Minus Buttons) only Start & Stop buttons.

    program Beeps at Regular intervals of 5 mins ( i,e 4,9,14,19 etc), there is no Current Time EQUALS SET TIME Checking routine

    Kindly Check the Program code

    Arun
  3. Binu

    Binu Administrator

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    The Reset switch is connected to the microcontroller reset pin. so the program will restarted.
    This timer wont have start or stop time, it will continiously run.

    J.Binu
    thilina likes this.
  4. alankargarude

    alankargarude New Member

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    hi binu

    in this circuit you have used a 20 pin microcontroller. Is the 20 pin atmel programmer readily available in the market? Is it possible to program AT802051 using a 40 pin programmer? i have seen the circuit of the programmer on this site, but i want to know whether a 20 pin atmel programmer will be available in the market or not?
  5. Binu

    Binu Administrator

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  6. solangi01

    solangi01 New Member

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    dear i like the made of countdown timer but hex file is not available
    asm file timer.a51 file is not working in assembler progremmer 40 and abovt error in asm files (timer.a51) please help me i am very thankful to you

    Naeem Solangi
    solangi01@yahoo.com
  7. qronoz

    qronoz New Member

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    @solangi
    binu has just told me that you just have to change its extension with .asm instead of .a51.. :)
  8. Binu

    Binu Administrator

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  9. qronoz

    qronoz New Member

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    according to nura's post, i want to ask some question:
    1. it's not clear for me about the function of start/stop button, could you tell me what will happen if i press start, and what if i press stop?
    2. does the time is fixed counting down from 99'59"?
  10. Binu

    Binu Administrator

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    When you press the start button the timer will start displaying the time on the display as
    00.00 then 00.01 thus it increments for every second so a maxmimum of 99mins & 99secs can be counted.

    The timer will run until you press the stop button.

    J.Binu
    Click here to get free 8051 Codes
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