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Digital Countdown Timer (AT89C2051)

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

  1. alankargarude

    alankargarude New Member

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    if the counter is counting from up, how can it be called countdown timer?? I assembled this circuit and have got the count starting from 0000.
  2. Binu

    Binu Administrator

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  3. qronoz

    qronoz New Member

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    can i set the buzzer to buzz on 30mins-30mins-30mins-10mins?
  4. Binu

    Binu Administrator

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  5. qronoz

    qronoz New Member

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    1. i've read it but i'm kinda newbie here, so can you give an example for adding first 30minute buzz?

    DELAY:
    MOV R1,#0FFH
    RAP2: MOV R2,#0FFH
    RAP1: NOP
    DJNZ R2,RAP1
    DJNZ R1,RAP2
    RET

    2. does it makes any sense if i change 1uF/15V capasitor with 1uF/50V capasitor?

    3. i've decided to use AT89s51 instead of AT89c2051, what should i mention in that change?
  6. Binu

    Binu Administrator

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    1. if you want to switch on buzzer for every 30 mins, please add the following code on line number 134.
    MOV A,MIN
    CJNE A,#30,FGVC3
    SETB BUZZER
    CALL DELAY
    CLR BUZZER
    CALL DELAY
    SETB BUZZER
    AJMP DOWN1
    FGVC3:

    2. No no change will happen, you can use 1uF/50v capacitor
    3. Yes you can use 89c51, but take care of the ports.

    J.Binu
    Click here to get free 8051 Codes
  7. qronoz

    qronoz New Member

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    1. so if i want to add buzz on XX minute, i just need to change
    CJNE A,#30,FGVC3
    is it right?

    2. when i buy the component, i'm kinda confused in picking 89s51 or 89c51, but my friend told me to pick 89s51 one.. is it wrong? am i gonna messed up with timer?

    3. 89s51 has 40-pin, if i take a look at data sheet of 89c2051, it only has port 1 and 3, does it means i dont have to use 89s51's port 0 and 2?
  8. Binu

    Binu Administrator

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    1. Yes you are correct. The line shown here will switch on the buzzer on 30 minutes.
    2. 89S51 and 89C51 are same but the programming interface is only changed. You dont need to worry about it.
    3. Yes you are correct, leave the other two ports and use only the ports as in the 89c2051. But dont change the ports.

    J.Binu
    Click here to get free 8051 Codes
  9. qronoz

    qronoz New Member

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    thx for the info, i'll try to build it soon.. :)

    if i didn't put additional routine buzz, is it only buzz when it reach 100 minutes?
  10. Binu

    Binu Administrator

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