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Creative Design Problem -- Thanks ALL! — Parallax Forums

Creative Design Problem -- Thanks ALL!

ArchiverArchiver Posts: 46,084
edited 2003-10-14 19:54 in General Discussion
Thank you everyone for the outstanding input to the water bowl design
problem! The question was "how do u detect water level for a full or empty
bowl".
There were SO many ways to do it, and after reading everyone's idea, I stumbled
upon an incredible and simple approach.

I constructed a small circuit composed of one capacitor and 2 resistors,
similar to the circuit given for RCTIME in the manual. But what I did was to
intentionally create an open circuit between the resistor and ground. We all
know
current doesnt flow in an open circuit. I placed the open part of the circuit
into the top level of an empty water bowl and told the microprocessor "if
current =0, then water is empty"

Now when the water begins to fill, guess what happens? The water rises and
then touches the open in the circuit. The amazing thing is that the water
actually completes the circuit! Water is actually behaving like a high
resistance
conductor. At this point current is not zero, because there is now a current
running from the circuit, in through the water, and then back to the circuit.

I wouldnt recommend this approach for determining fuel level though. I dont
know about you guys, but i wouldnt want to ride in a car whose fuel gage
operates by running a small current through gasoline [noparse]:)[/noparse]

Mike


[noparse][[/noparse]Non-text portions of this message have been removed]

Comments

  • ArchiverArchiver Posts: 46,084
    edited 2003-10-14 13:45
    Just a bit of information for you. Most fuel gauge sender units used in
    cars actually are variable resistors with a float on the wiper. The wire
    wound resistor element is usually in the fuel and current does run through
    it. This is a voltage divider and the gauge just responds to the change in
    resistance.

    jim
    http://www.geocities.com/jimforkin2003/


    Original Message
    From: MP1428@a... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=E-E_2pjGV1vnxD0CTjmyq-DaHOKIMLOBUnQO1_Z9leSe8zDEoOm3DSUPsiv_h9LKGFvgj6hE]MP1428@a...[/url
    Sent: Monday, October 13, 2003 9:52 PM
    To: basicstamps@yahoogroups.com
    Subject: [noparse][[/noparse]basicstamps] Creative Design Problem -- Thanks ALL!


    Thank you everyone for the outstanding input to the water bowl design
    problem! The question was "how do u detect water level for a full or empty
    bowl".
    There were SO many ways to do it, and after reading everyone's idea, I
    stumbled
    upon an incredible and simple approach.

    I constructed a small circuit composed of one capacitor and 2 resistors,
    similar to the circuit given for RCTIME in the manual. But what I did was to
    intentionally create an open circuit between the resistor and ground. We all
    know
    current doesnt flow in an open circuit. I placed the open part of the
    circuit
    into the top level of an empty water bowl and told the microprocessor "if
    current =0, then water is empty"

    Now when the water begins to fill, guess what happens? The water rises and
    then touches the open in the circuit. The amazing thing is that the water
    actually completes the circuit! Water is actually behaving like a high
    resistance
    conductor. At this point current is not zero, because there is now a current
    running from the circuit, in through the water, and then back to the
    circuit.

    I wouldnt recommend this approach for determining fuel level though. I dont
    know about you guys, but i wouldnt want to ride in a car whose fuel gage
    operates by running a small current through gasoline [noparse]:)[/noparse]

    Mike


    [noparse][[/noparse]Non-text portions of this message have been removed]


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    [noparse][[/noparse]Non-text portions of this message have been removed]
  • ArchiverArchiver Posts: 46,084
    edited 2003-10-14 14:34
    In a message dated 10/14/2003 5:46:37 AM Pacific Daylight Time,
    jjf@p... writes:
    Just a bit of information for you. Most fuel gauge sender units used in
    cars actually are variable resistors with a float on the wiper. The wire
    wound resistor element is usually in the fuel and current does run through
    it. This is a voltage divider and the gauge just responds to the change in
    resistance.
    ++++++++++++++++++++++++++++++++++++++++

    True for the fuel gauge, but not for the low fuel warning lamp. The low fuel
    indicator lamp is completely independent of the fuel gauge circuit on MOST
    cars.

    Ken


    [noparse][[/noparse]Non-text portions of this message have been removed]
  • ArchiverArchiver Posts: 46,084
    edited 2003-10-14 16:05
    In a message dated 10/13/2003 6:55:26 PM Pacific Daylight Time,
    MP1428@a... writes:
    I wouldnt recommend this approach for determining fuel level though. I dont
    know about you guys, but i wouldnt want to ride in a car whose fuel gage
    operates by running a small current through gasoline [noparse]:)[/noparse]

    Mike
    ++++++++++++++++++++++++++++++++++

    Got news for you, the fuel gauge with current in it is immersed in
    gasoline......see the post by JIM. His description is spot on!!!!!!!!


    [noparse][[/noparse]Non-text portions of this message have been removed]
  • ArchiverArchiver Posts: 46,084
    edited 2003-10-14 16:37
    Gasoline is a dielectric and won't conduct electricity. By the way
    some of the low fuel level lights are turned on by wound aircore
    capacitors whose capacitive reactance is measured.

    --- smartdim@a... wrote:
    > In a message dated 10/13/2003 6:55:26 PM Pacific Daylight Time,
    > MP1428@a... writes:
    > I wouldnt recommend this approach for determining fuel level though.
    > I dont
    > know about you guys, but i wouldnt want to ride in a car whose fuel
    > gage
    > operates by running a small current through gasoline [noparse]:)[/noparse]
    >
    > Mike
    > ++++++++++++++++++++++++++++++++++
    >
    > Got news for you, the fuel gauge with current in it is immersed in
    > gasoline......see the post by JIM. His description is spot on!!!!!!!!
    >
    >
    > [noparse][[/noparse]Non-text portions of this message have been removed]
    >
    >
    > To UNSUBSCRIBE, just send mail to:
    > basicstamps-unsubscribe@yahoogroups.com
    > from the same email address that you subscribed. Text in the Subject
    > and Body of the message will be ignored.
    >
    >
    > Your use of Yahoo! Groups is subject to
    > http://docs.yahoo.com/info/terms/
    >
    >


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  • ArchiverArchiver Posts: 46,084
    edited 2003-10-14 19:37
    Yup, in every old car I ever tore apart in my misspent youth, the fuel gauge
    sensor was a wire-wound potentiometer thingie right down in the gasoline
    with the float-arm moving the contact. Even back then it was a little scary
    to contemplate what would happen if that nichrome wire wore through and
    sparked when the contact bridged the gap. I've never heard of a fuel tank
    explosion from that sort of thing, except for perhaps TWA Flight 800.

    Food for thought, isn't it?

    Mike Sokol
    www.modernrecording.com
    mikes@m...


    " One should not increase, beyond what is necessary,
    the number of entities required to explain anything"...
    -William of Occam-

    Original Message
    From: <smartdim@a...>
    To: <basicstamps@yahoogroups.com>
    Sent: Tuesday, October 14, 2003 11:05 AM
    Subject: Re: [noparse][[/noparse]basicstamps] Creative Design Problem -- Thanks ALL!


    > In a message dated 10/13/2003 6:55:26 PM Pacific Daylight Time,
    > MP1428@a... writes:
    > I wouldnt recommend this approach for determining fuel level though. I
    dont
    > know about you guys, but i wouldnt want to ride in a car whose fuel gage
    > operates by running a small current through gasoline [noparse]:)[/noparse]
    >
    > Mike
    > ++++++++++++++++++++++++++++++++++
    >
    > Got news for you, the fuel gauge with current in it is immersed in
    > gasoline......see the post by JIM. His description is spot on!!!!!!!!
    >
    >
    > [noparse][[/noparse]Non-text portions of this message have been removed]
    >
    >
    > To UNSUBSCRIBE, just send mail to:
    > basicstamps-unsubscribe@yahoogroups.com
    > from the same email address that you subscribed. Text in the Subject and
    Body of the message will be ignored.
    >
    >
    > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
    >
    >
  • ArchiverArchiver Posts: 46,084
    edited 2003-10-14 19:54
    I am a flightline mechanic for Boeing. Don't believe everything you
    hear or read about Flight 800.

    I've never heard of a fuel
    > tank
    > explosion from that sort of thing, except for perhaps TWA Flight 800.
    >
    > Food for thought, isn't it?
    >
    > Mike Sokol
    > www.modernrecording.com
    > mikes@m...
    >
    >
    > " One should not increase, beyond what is necessary,
    > the number of entities required to explain anything"...
    > -William of Occam-
    >
    >
    Original Message
    > From: <smartdim@a...>
    > To: <basicstamps@yahoogroups.com>
    > Sent: Tuesday, October 14, 2003 11:05 AM
    > Subject: Re: [noparse][[/noparse]basicstamps] Creative Design Problem -- Thanks ALL!
    >
    >
    > > In a message dated 10/13/2003 6:55:26 PM Pacific Daylight Time,
    > > MP1428@a... writes:
    > > I wouldnt recommend this approach for determining fuel level
    > though. I
    > dont
    > > know about you guys, but i wouldnt want to ride in a car whose fuel
    > gage
    > > operates by running a small current through gasoline [noparse]:)[/noparse]
    > >
    > > Mike
    > > ++++++++++++++++++++++++++++++++++
    > >
    > > Got news for you, the fuel gauge with current in it is immersed in
    > > gasoline......see the post by JIM. His description is spot
    > on!!!!!!!!
    > >
    > >
    > > [noparse][[/noparse]Non-text portions of this message have been removed]
    > >
    > >
    > > To UNSUBSCRIBE, just send mail to:
    > > basicstamps-unsubscribe@yahoogroups.com
    > > from the same email address that you subscribed. Text in the
    > Subject and
    > Body of the message will be ignored.
    > >
    > >
    > > Your use of Yahoo! Groups is subject to
    > http://docs.yahoo.com/info/terms/
    > >
    > >
    >
    >
    >
    >
    > To UNSUBSCRIBE, just send mail to:
    > basicstamps-unsubscribe@yahoogroups.com
    > from the same email address that you subscribed. Text in the Subject
    > and Body of the message will be ignored.
    >
    >
    > Your use of Yahoo! Groups is subject to
    > http://docs.yahoo.com/info/terms/
    >
    >


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