Urgent Circuits help needed

Discussion in 'Computer Science & Culture' started by Truenemo1889, Oct 4, 2004.

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  1. Truenemo1889 Registered Senior Member

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    Hello Everyone,

    I have problem with throttle position sensor circuit. The theoretical setup of the circuit is as follows.

    Throttle (potentiometer/rheostat) === Analog Digital Converter (with 8 BIT Output) === BDC to 7 segment decoder (7447) === 2 x 7-Segment displays (7730)

    The analog digital converter gives me an 8 bit output accoriding to the position of the throttle.

    Conditons at specfic positions

    Throttle position: open (0 degrees) , rheostat output voltage:0.5 V, Bit pattern:00011010,

    Throttle position: halfway open (45 degrees), rheostat output voltage: 2.5 V, bit patten: 10000000

    Throttle position: closed (90 degrees), rheostat output voltage: 4.5 V, bit pattern: 11100110


    My teacher wants the two 7 segment indicators to say 0 at the open postion

    50 at half closed/open postion and about 99 at the closed postion. Anything beyong this interval should give an error message.

    How can i achieve this. When i and my classmates tried to connect the output of the analog digital converter to the 7 segment indicator and changed the position of the throttle we got real numbers. But the number werent going from 0-99., but from 10 to over 99 , at which the indicator started to display nonsense.

    Should i use an EPROM chip (a programable logic chip) to be able to display number within 00-99.

    The funny thing is that our techer told us that we couldn't use an EPROM chip, while the students of the last semester could.

    Any help would be greatly appreciated
     
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  3. melodicbard Registered Senior Member

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    I doubt if the output of the ADC is in BCD format. Please check.
    Add extra logic to convert binary to BCD representation before feeding the signals to the 7-segment.

    The ADC gives
    0.5 -> 26 (decimal)
    2.5 -> 128
    4.5 -> 230

    You can see that 2V corresponds to 102 steps
    At reading 0 i.e. output = 00000000, the voltage should be about 0V.
    At reding 99, i.e. output = 01100011, the voltage should be about 1.94V.
    Add some potential divider network to adjust the voltage range to the desired one.

    Hope that helps
     
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