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threshold for 0 and 1 — Parallax Forums

threshold for 0 and 1

ArchiverArchiver Posts: 46,084
edited 2003-06-20 19:41 in General Discussion
I have a pin from IC that outputs 1.1 V. BS2 pin is reading this
voltage. BS2 interprets 1.1 V as "1" (high).

What is the voltage range that BS2 will interpret as 0? As 1?

Much thanks in advance.

Comments

  • ArchiverArchiver Posts: 46,084
    edited 2003-06-18 22:41
    In a message dated 6/18/2003 3:18:42 PM Eastern Daylight Time,
    basicstampede@y... writes:

    >
    > I have a pin from IC that outputs 1.1 V. BS2 pin is reading this
    > voltage. BS2 interprets 1.1 V as "1" (high).
    >
    > What is the voltage range that BS2 will interpret as 0? As 1?
    >
    > Much thanks in advance.
    >
    >

    If I dust off the cobwebs I believe, without looking for my ancient college
    texts, that in the digital domain:
    Zero is .7 volts or less
    One is 2.7 volts to 5 volts
    Anything in the middle is no mans land. The circuit will do as it wants. It
    is best to stay out of there. Digital is more time sensitive than voltage
    sensitive.
    If you need to sense a voltage level than go to an analog voltage comparator
    or A/D Converter.

    Hope this helps.
    Alan Bradford
    Plasma Technologies


    [noparse][[/noparse]Non-text portions of this message have been removed]
  • ArchiverArchiver Posts: 46,084
    edited 2003-06-18 23:17
    The BS2 switching threshold is approximately 1.5 volts.

    -- Jon Williams
    -- Parallax

    In a message dated 6/18/2003 2:18:27 PM Central Standard Time,
    basicstampede@y... writes:

    > I have a pin from IC that outputs 1.1 V. BS2 pin is reading this
    > voltage. BS2 interprets 1.1 V as "1" (high).
    >
    > What is the voltage range that BS2 will interpret as 0? As 1?
    >
    > Much thanks in advance.



    [noparse][[/noparse]Non-text portions of this message have been removed]
  • ArchiverArchiver Posts: 46,084
    edited 2003-06-19 15:43
    Thank you. When I chang the pull up resistor to 100 K, the voltage
    drops to around 0.85 Volts, and now Basic Stamp2 correctly reads it
    as "0".


    --- In basicstamps@yahoogroups.com, plasmastamp@a... wrote:
    > In a message dated 6/18/2003 3:18:42 PM Eastern Daylight Time,
    > basicstampede@y... writes:
    >
    > >
    > > I have a pin from IC that outputs 1.1 V. BS2 pin is reading this
    > > voltage. BS2 interprets 1.1 V as "1" (high).
    > >
    > > What is the voltage range that BS2 will interpret as 0? As 1?
    > >
    > > Much thanks in advance.
    > >
    > >
    >
    > If I dust off the cobwebs I believe, without looking for my ancient
    college
    > texts, that in the digital domain:
    > Zero is .7 volts or less
    > One is 2.7 volts to 5 volts
    > Anything in the middle is no mans land. The circuit will do as it
    wants. It
    > is best to stay out of there. Digital is more time sensitive than
    voltage
    > sensitive.
    > If you need to sense a voltage level than go to an analog voltage
    comparator
    > or A/D Converter.
    >
    > Hope this helps.
    > Alan Bradford
    > Plasma Technologies
    >
    >
    > [noparse][[/noparse]Non-text portions of this message have been removed]
  • ArchiverArchiver Posts: 46,084
    edited 2003-06-20 19:41
    I have my students run an experiment on this topic. They set up a
    voltage divider as an input to the BS2. The program they download
    just reports (debugs) whether the I/O pin is high or low. As they
    adjust the voltage divider with a trimmer pot, they see a series of
    high and eventually a low on the debug screen. When they see the
    transition, they stop adjusting the pot and measure the voltage
    drop.

    They find the tranistion occurs at 1.4 volts, or at two p-n junction
    drops.

    Paul

    > In a message dated 6/18/2003 3:18:42 PM Eastern Daylight Time,
    > basicstampede@y... writes:
    >
    > >
    > > I have a pin from IC that outputs 1.1 V. BS2 pin is reading this
    > > voltage. BS2 interprets 1.1 V as "1" (high).
    > >
    > > What is the voltage range that BS2 will interpret as 0? As 1?
    > >
    > > Much thanks in advance.
    > >
    > >
    >
    > If I dust off the cobwebs I believe, without looking for my ancient college
    > texts, that in the digital domain:
    > Zero is .7 volts or less
    > One is 2.7 volts to 5 volts
    > Anything in the middle is no mans land. The circuit will do as it wants. It
    > is best to stay out of there. Digital is more time sensitive than voltage
    > sensitive.
    > If you need to sense a voltage level than go to an analog voltage comparator
    > or A/D Converter.
    >
    > Hope this helps.
    > Alan Bradford
    > Plasma Technologies
    >
    >
    > [noparse][[/noparse]Non-text portions of this message have been removed]
    >
    >
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