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interfacing ADC0808 with 89C51

Discussion in 'Microcontrollers' started by mnoman, Jun 29, 2006.

  1. mnoman

    mnoman New Member

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    hello can any one tell me how to interface ADC0808 with 89C51 especially how to provide clock to the ADC and at what frequency
     
  2. Paul Obrien

    Paul Obrien Guest

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    The clock frequency can be from 10KHz to 1200KHz, the interfacing depends on wheter you leave the ADC free-running or start it for each conversion(I prefer free-running). The clock freq is abt 10 higher than the sample rate (memory) and the EOC end of conversion output is used as an interrupt. I still have one of these around somewhere.
     
  3. mnoman

    mnoman New Member

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    Will it be better to provide clock using 555 IC
     
  4. dave

    Dave New Member

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  5. Paul Obrien

    Paul Obrien Guest

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    555s are using the same components that the free running osc on the 0808 would use and therefore contribute to complexity but add nothing.
     
  6. Papabravo

    Papabravo Well-Known Member

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    Why not have the uP provide the clock? Seems like Timer2 with an output pin might be just the ticket.
     
  7. mnoman

    mnoman New Member

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    do any one have code for interfacing ADC0808 with 89C51
     
  8. Paul Obrien

    Paul Obrien Guest

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  9. bibinjohn

    bibinjohn New Member

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  10. mnoman

    mnoman New Member

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  11. Paul Obrien

    Paul Obrien Guest

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    Last edited by a moderator: Jul 6, 2006
  12. mnoman

    mnoman New Member

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    I am using clock from 555 IC using 388KHz freq i am using R1=4.7k R2= 10K and C=150pF is this ok where as the anlog input is from the LM35
     
  13. Paul Obrien

    Paul Obrien Guest

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    Yes the spec shows anything between 10KHz 1200KHZ is OK, and for a test circuit like this, the input should be a DC voltage as an AC input would light most of the LEDs at some point. The idea of this circuit is to prove the 0808 is working, that's all.
     
  14. mnoman

    mnoman New Member

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    ok I tested this circuit but some times all the outputs become high(logic 1) and somtimes some of them but i am not getting the correct result, any ideas
     
  15. Paul Obrien

    Paul Obrien Guest

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    if you are using an AC(ie audio) this will occur try using a variable resistor between 0 and 5V as a dc source
     
  16. mnoman

    mnoman New Member

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    I just tied one of the analog inputs to the +5V, then all outputs must be at logic 1 but this does not happens
     
  17. Paul Obrien

    Paul Obrien Guest

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    Are you still using the test circuit, if so then all the LEDs except 1 should be light.
     
  18. mnoman

    mnoman New Member

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    another ckt that i want to test is of a IR proximity sensor I actually want to have a distance of atleast 1m or 2m from the obstacle anyone having the idea plz help me
     
  19. mnoman

    mnoman New Member

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    any one reply to proximity sensor and ADC0808
     
  20. ishank thandi

    ishank thandi New Member

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    ur problem solved

    hi,
    im ishank.first generate clock pulse as a output via 555timer on pin3 then connect it on pin10 of adc 0808.frequency should be max of 640 KHz .


    GOOD LUCK:p
     
  21. ishank thandi

    ishank thandi New Member

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    Hi,
    im ishank.first generate clock pulse as a output via 555timer on pin3 then connect it on pin10 of adc 0808.frequency should be max of 640 KHz .
     

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