Brilliant idea needed!!!

Discussion in 'Electronic Design' started by Geocacher, Sep 22, 2005.

  1. Geocacher

    Geocacher Guest

    I work in the trailer manufacturing business.
    We use LED tail-light clusters.
    The modern truck/tractors utilise a computer system to perform diagnostics
    on various systems within the rig. One of these is the lighting system.
    A pulse is sent to each tail light, the system monitoring the current. If
    there is current flow, it is assumed the incandescent globes are OK.

    Unfortunately, the LED lamps draw such a small amount of current that the
    computer does not see a "filament" and flags a major fault on the truck
    dashboard. In addition to the error message, the system continues to send
    curent pulss in the forlorn hope that things at the rear of the rig have
    improved. This causes the entire suite of LED lamps to flash like a
    low-class disco!

    There are ways around it. Some manufacturers have placed incandescent globes
    in parallel with the LED lamps, others have used high wattage resistors.
    Neither is acceptable for obvious reasons.

    There must be a way to "tell" the computer that the LED lamps are fine by
    emulating the current drawn by an incandescent globe, without using the
    solutions noted above.

    Do any of you outstandingly brilliant contributors have any novel and
    innovative ideas?????
     
    Geocacher, Sep 22, 2005
    #1
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  2. Geocacher

    Anno Siegel Guest

    Geocacher <> wrote in sci.electronics.design:
    > I work in the trailer manufacturing business.
    > We use LED tail-light clusters.
    > The modern truck/tractors utilise a computer system to perform diagnostics
    > on various systems within the rig. One of these is the lighting system.
    > A pulse is sent to each tail light, the system monitoring the current. If
    > there is current flow, it is assumed the incandescent globes are OK.
    >
    > Unfortunately, the LED lamps draw such a small amount of current that the
    > computer does not see a "filament" and flags a major fault on the truck
    > dashboard. In addition to the error message, the system continues to send
    > curent pulss in the forlorn hope that things at the rear of the rig have
    > improved. This causes the entire suite of LED lamps to flash like a
    > low-class disco!
    >
    > There are ways around it. Some manufacturers have placed incandescent globes
    > in parallel with the LED lamps, others have used high wattage resistors.
    > Neither is acceptable for obvious reasons.
    >
    > There must be a way to "tell" the computer that the LED lamps are fine by
    > emulating the current drawn by an incandescent globe, without using the
    > solutions noted above.


    The test you describe is applicable while the tail-lights are off. Does
    the diagnostic system permanently monitor the current when they are
    switched on? If so, I don't see a simple solution except re-calibrating
    the current the diagnostic system expects.

    For the test you describe you could use the parallel resistor, but switch
    it off after a second or so of power. The duration must be long enough
    to cover the test pulse and short enough not to cause excess power
    consumption in the long run. A more sophisticated solution would check
    if the LED array draws the expected current and only add the parallel
    resistor if it does.

    Anno
    --
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    Anno Siegel, Sep 22, 2005
    #2
    1. Advertising

  3. " Geocacher" <> wrote in message
    news:dgu6ht$g24$...
    > I work in the trailer manufacturing business.
    > We use LED tail-light clusters.
    > The modern truck/tractors utilise a computer system to perform diagnostics
    > on various systems within the rig. One of these is the lighting system.
    > A pulse is sent to each tail light, the system monitoring the current. If
    > there is current flow, it is assumed the incandescent globes are OK.
    >
    > Unfortunately, the LED lamps draw such a small amount of current that the
    > computer does not see a "filament" and flags a major fault on the truck
    > dashboard. In addition to the error message, the system continues to send
    > curent pulss in the forlorn hope that things at the rear of the rig have
    > improved. This causes the entire suite of LED lamps to flash like a
    > low-class disco!


    The first thing that comes to mind is to place a lage capacitor (1000uF?)
    across the LEDS, to draw a high current pulse during the test, providing the
    test is short enough. But I suspect this will flash the lights as well since
    the cap is discharged through the LED's.

    Meindert
     
    Meindert Sprang, Sep 22, 2005
    #3
  4. In article <>,
    says...
    > " Geocacher" <> wrote in message
    > news:dgu6ht$g24$...
    > > I work in the trailer manufacturing business.
    > > We use LED tail-light clusters.
    > > The modern truck/tractors utilise a computer system to perform diagnostics
    > > on various systems within the rig. One of these is the lighting system.
    > > A pulse is sent to each tail light, the system monitoring the current. If
    > > there is current flow, it is assumed the incandescent globes are OK.
    > >
    > > Unfortunately, the LED lamps draw such a small amount of current that the
    > > computer does not see a "filament" and flags a major fault on the truck
    > > dashboard. In addition to the error message, the system continues to send
    > > curent pulss in the forlorn hope that things at the rear of the rig have
    > > improved. This causes the entire suite of LED lamps to flash like a
    > > low-class disco!

    >
    > The first thing that comes to mind is to place a lage capacitor (1000uF?)
    > across the LEDS, to draw a high current pulse during the test, providing the
    > test is short enough. But I suspect this will flash the lights as well since
    > the cap is discharged through the LED's.


    How about a diode in series with the cap to isolate the LEDs? Maybe a
    resistor across the cap to discharge it since the LEDs won't.

    --
    Keith
     
    Keith Williams, Sep 22, 2005
    #4
  5. Geocacher

    Tim Wescott Guest

    Geocacher wrote:
    > I work in the trailer manufacturing business.
    > We use LED tail-light clusters.
    > The modern truck/tractors utilise a computer system to perform diagnostics
    > on various systems within the rig. One of these is the lighting system.
    > A pulse is sent to each tail light, the system monitoring the current. If
    > there is current flow, it is assumed the incandescent globes are OK.
    >
    > Unfortunately, the LED lamps draw such a small amount of current that the
    > computer does not see a "filament" and flags a major fault on the truck
    > dashboard. In addition to the error message, the system continues to send
    > curent pulss in the forlorn hope that things at the rear of the rig have
    > improved. This causes the entire suite of LED lamps to flash like a
    > low-class disco!
    >
    > There are ways around it. Some manufacturers have placed incandescent globes
    > in parallel with the LED lamps, others have used high wattage resistors.
    > Neither is acceptable for obvious reasons.
    >
    > There must be a way to "tell" the computer that the LED lamps are fine by
    > emulating the current drawn by an incandescent globe, without using the
    > solutions noted above.
    >
    > Do any of you outstandingly brilliant contributors have any novel and
    > innovative ideas?????
    >
    >

    Eventually the computer manufacturers will get off their duffs and
    correct _their_ problem. Call them up, tell them LED tail lights have
    been on the market for years, and ask them which one of their
    competitors does the job right.

    --

    Tim Wescott
    Wescott Design Services
    http://www.wescottdesign.com
     
    Tim Wescott, Sep 22, 2005
    #5
  6. Geocacher

    Fred Bloggs Guest

    Geocacher wrote:
    > I work in the trailer manufacturing business.
    > We use LED tail-light clusters.
    > The modern truck/tractors utilise a computer system to perform diagnostics
    > on various systems within the rig. One of these is the lighting system.
    > A pulse is sent to each tail light, the system monitoring the current. If
    > there is current flow, it is assumed the incandescent globes are OK.
    >
    > Unfortunately, the LED lamps draw such a small amount of current that the
    > computer does not see a "filament" and flags a major fault on the truck
    > dashboard. In addition to the error message, the system continues to send
    > curent pulss in the forlorn hope that things at the rear of the rig have
    > improved. This causes the entire suite of LED lamps to flash like a
    > low-class disco!
    >
    > There are ways around it. Some manufacturers have placed incandescent globes
    > in parallel with the LED lamps, others have used high wattage resistors.
    > Neither is acceptable for obvious reasons.
    >
    > There must be a way to "tell" the computer that the LED lamps are fine by
    > emulating the current drawn by an incandescent globe, without using the
    > solutions noted above.
    >
    > Do any of you outstandingly brilliant contributors have any novel and
    > innovative ideas?????
    >
    >


    Easily and obviously fixed but how much do you want to pay for the
    answer????
     
    Fred Bloggs, Sep 22, 2005
    #6
  7. Geocacher

    Fred Bartoli Guest

    " Geocacher" <> a écrit dans le message de
    news:dgu6ht$g24$...
    > I work in the trailer manufacturing business.
    > We use LED tail-light clusters.
    > The modern truck/tractors utilise a computer system to perform diagnostics
    > on various systems within the rig. One of these is the lighting system.
    > A pulse is sent to each tail light, the system monitoring the current. If
    > there is current flow, it is assumed the incandescent globes are OK.
    >
    > Unfortunately, the LED lamps draw such a small amount of current that the
    > computer does not see a "filament" and flags a major fault on the truck
    > dashboard. In addition to the error message, the system continues to send
    > curent pulss in the forlorn hope that things at the rear of the rig have
    > improved. This causes the entire suite of LED lamps to flash like a
    > low-class disco!
    >
    > There are ways around it. Some manufacturers have placed incandescent

    globes
    > in parallel with the LED lamps, others have used high wattage resistors.
    > Neither is acceptable for obvious reasons.
    >
    > There must be a way to "tell" the computer that the LED lamps are fine by
    > emulating the current drawn by an incandescent globe, without using the
    > solutions noted above.
    >
    > Do any of you outstandingly brilliant contributors have any novel and
    > innovative ideas?????
    >


    You can have the information in about 50ms if you pay me the right price.


    --
    Thanks,
    Fred.
     
    Fred Bartoli, Sep 22, 2005
    #7
  8. Geocacher

    Geocacher Guest

    The payment you request would be adequately supplied by the outright
    admiration of your peers on this forum. They (me included) would bow our
    heads in honour of the man who could fix the problem in 50mS!


    "Fred Bartoli"
    <fred._canxxxel_this_bartoli@RemoveThatAlso_free.fr_AndThisToo> wrote in
    message news:4332d190$0$21208$...
    >
    > " Geocacher" <> a écrit dans le message de
    > news:dgu6ht$g24$...
    >> I work in the trailer manufacturing business.
    >> We use LED tail-light clusters.
    >> The modern truck/tractors utilise a computer system to perform
    >> diagnostics
    >> on various systems within the rig. One of these is the lighting system.
    >> A pulse is sent to each tail light, the system monitoring the current. If
    >> there is current flow, it is assumed the incandescent globes are OK.
    >>
    >> Unfortunately, the LED lamps draw such a small amount of current that the
    >> computer does not see a "filament" and flags a major fault on the truck
    >> dashboard. In addition to the error message, the system continues to send
    >> curent pulss in the forlorn hope that things at the rear of the rig have
    >> improved. This causes the entire suite of LED lamps to flash like a
    >> low-class disco!
    >>
    >> There are ways around it. Some manufacturers have placed incandescent

    > globes
    >> in parallel with the LED lamps, others have used high wattage resistors.
    >> Neither is acceptable for obvious reasons.
    >>
    >> There must be a way to "tell" the computer that the LED lamps are fine by
    >> emulating the current drawn by an incandescent globe, without using the
    >> solutions noted above.
    >>
    >> Do any of you outstandingly brilliant contributors have any novel and
    >> innovative ideas?????
    >>

    >
    > You can have the information in about 50ms if you pay me the right price.
    >
    >
    > --
    > Thanks,
    > Fred.
    >
    >
     
    Geocacher, Sep 22, 2005
    #8
  9. Geocacher

    Jim Thompson Guest

    On Thu, 22 Sep 2005 14:02:56 +0200, " Geocacher" <> wrote:

    >I work in the trailer manufacturing business.
    >We use LED tail-light clusters.
    >The modern truck/tractors utilise a computer system to perform diagnostics
    >on various systems within the rig. One of these is the lighting system.
    >A pulse is sent to each tail light, the system monitoring the current. If
    >there is current flow, it is assumed the incandescent globes are OK.
    >
    >Unfortunately, the LED lamps draw such a small amount of current that the
    >computer does not see a "filament" and flags a major fault on the truck
    >dashboard. In addition to the error message, the system continues to send
    >curent pulss in the forlorn hope that things at the rear of the rig have
    >improved. This causes the entire suite of LED lamps to flash like a
    >low-class disco!
    >
    >There are ways around it. Some manufacturers have placed incandescent globes
    >in parallel with the LED lamps, others have used high wattage resistors.
    >Neither is acceptable for obvious reasons.
    >
    >There must be a way to "tell" the computer that the LED lamps are fine by
    >emulating the current drawn by an incandescent globe, without using the
    >solutions noted above.
    >
    >Do any of you outstandingly brilliant contributors have any novel and
    >innovative ideas?????
    >


    The computer doesn't send the pulse, it instructs the "system" to send
    the pulse and measure the response.

    Change your algorithm, so the response is meaningful... maybe trickle
    100uA and measure the voltage... LED's ARE junction devices, you know?

    ...Jim Thompson
    --
    | James E.Thompson, P.E. | mens |
    | Analog Innovations, Inc. | et |
    | Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
    | Phoenix, Arizona Voice:(480)460-2350 | |
    | E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
    | http://www.analog-innovations.com | 1962 |

    I love to cook with wine. Sometimes I even put it in the food.
     
    Jim Thompson, Sep 22, 2005
    #9
  10. Geocacher

    Fred Bartoli Guest

    " Geocacher" <> a écrit dans le message de
    news:dguk7a$b53$...
    > The payment you request would be adequately supplied by the outright
    > admiration of your peers on this forum. They (me included) would bow our
    > heads in honour of the man who could fix the problem in 50mS!
    >
    >


    The answer was in the answer. Just find it :)


    --
    Thanks,
    Fred.
     
    Fred Bartoli, Sep 22, 2005
    #10
  11. Geocacher <> wrote:

    > I work in the trailer manufacturing business.
    > We use LED tail-light clusters.
    > The modern truck/tractors utilise a computer system to perform diagnostics
    > on various systems within the rig. One of these is the lighting system.
    > A pulse is sent to each tail light, the system monitoring the current. If
    > there is current flow, it is assumed the incandescent globes are OK.
    >
    > Unfortunately, the LED lamps draw such a small amount of current that the
    > computer does not see a "filament" and flags a major fault on the truck
    > dashboard. In addition to the error message, the system continues to send
    > curent pulss in the forlorn hope that things at the rear of the rig have
    > improved. This causes the entire suite of LED lamps to flash like a
    > low-class disco!

    [...]
    >
    > Do any of you outstandingly brilliant contributors have any novel and
    > innovative ideas?????


    Get rid of the computer. It's probably less reliable than the LEDs
    anyway.

    --
    ~ Adrian Tuddenham ~
    (Remove the ".invalid"s and add ".co.uk" to reply)
    www.poppyrecords.co.uk
     
    Adrian Tuddenham, Sep 22, 2005
    #11
  12. Geocacher

    Geocacher Guest

    We cannot 'play' with the computer system aboard the truck/tractor, hence
    this enquiry. The solution must be attached to the trailer wiring in such a
    way that the truck's system is satisfied that the lights are functional.

    "Adrian Tuddenham" <> wrote in message
    news:1h3azov.v9jsrl1ub1tbeN%...
    > Geocacher <> wrote:
    >
    >> I work in the trailer manufacturing business.
    >> We use LED tail-light clusters.
    >> The modern truck/tractors utilise a computer system to perform
    >> diagnostics
    >> on various systems within the rig. One of these is the lighting system.
    >> A pulse is sent to each tail light, the system monitoring the current. If
    >> there is current flow, it is assumed the incandescent globes are OK.
    >>
    >> Unfortunately, the LED lamps draw such a small amount of current that the
    >> computer does not see a "filament" and flags a major fault on the truck
    >> dashboard. In addition to the error message, the system continues to send
    >> curent pulss in the forlorn hope that things at the rear of the rig have
    >> improved. This causes the entire suite of LED lamps to flash like a
    >> low-class disco!

    > [...]
    >>
    >> Do any of you outstandingly brilliant contributors have any novel and
    >> innovative ideas?????

    >
    > Get rid of the computer. It's probably less reliable than the LEDs
    > anyway.
    >
    > --
    > ~ Adrian Tuddenham ~
    > (Remove the ".invalid"s and add ".co.uk" to reply)
    > www.poppyrecords.co.uk
     
    Geocacher, Sep 22, 2005
    #12
  13. Geocacher

    Jim Thompson Guest

    On Thu, 22 Sep 2005 22:55:23 +0200, " Geocacher" <> wrote:

    >We cannot 'play' with the computer system aboard the truck/tractor, hence
    >this enquiry. The solution must be attached to the trailer wiring in such a
    >way that the truck's system is satisfied that the lights are functional.
    >
    >"Adrian Tuddenham" <> wrote in message
    >news:1h3azov.v9jsrl1ub1tbeN%...
    >> Geocacher <> wrote:
    >>
    >>> I work in the trailer manufacturing business.
    >>> We use LED tail-light clusters.
    >>> The modern truck/tractors utilise a computer system to perform
    >>> diagnostics
    >>> on various systems within the rig. One of these is the lighting system.
    >>> A pulse is sent to each tail light, the system monitoring the current. If
    >>> there is current flow, it is assumed the incandescent globes are OK.


    Not clear what you mean. Is "pulse" a VOLTAGE pulse and you measure
    the current?

    >>>
    >>> Unfortunately, the LED lamps draw such a small amount of current that the
    >>> computer does not see a "filament" and flags a major fault on the truck
    >>> dashboard. In addition to the error message, the system continues to send
    >>> curent pulss in the forlorn hope that things at the rear of the rig have
    >>> improved. This causes the entire suite of LED lamps to flash like a
    >>> low-class disco!


    CURRENT pulse?

    >> [...]
    >>>
    >>> Do any of you outstandingly brilliant contributors have any novel and
    >>> innovative ideas?????

    >>
    >> Get rid of the computer. It's probably less reliable than the LEDs
    >> anyway.
    >>
    >> --
    >> ~ Adrian Tuddenham ~
    >> (Remove the ".invalid"s and add ".co.uk" to reply)
    >> www.poppyrecords.co.uk

    >



    ...Jim Thompson
    --
    | James E.Thompson, P.E. | mens |
    | Analog Innovations, Inc. | et |
    | Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
    | Phoenix, Arizona Voice:(480)460-2350 | |
    | E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
    | http://www.analog-innovations.com | 1962 |

    I love to cook with wine. Sometimes I even put it in the food.
     
    Jim Thompson, Sep 22, 2005
    #13
  14. "Fred Bloggs" <> schreef in bericht
    news:...
    >
    > Geocacher wrote:
    > > There must be a way to "tell" the computer that the LED lamps are fine

    by
    > > emulating the current drawn by an incandescent globe, without using the
    > > solutions noted above.
    > >
    > > Do any of you outstandingly brilliant contributors have any novel and
    > > innovative ideas?????
    > >

    >
    > Easily and obviously fixed but how much do you want to pay for the
    > answer????


    I don't know. Can the current sensor (resistor?) be replaced, does
    the fix only fix the disco behaviour, or does it also fix the
    annoying error message?

    Perhaps a switcher could be used to make the LED units work at
    a much lower voltage, drawing a higher current. The remaining
    voltage could run a step-up switcher to dump that energy back
    into the battery.

    --
    Thanks, Frank.
    (remove 'q' and '.invalid' when replying by email)
     
    Frank Bemelman, Sep 22, 2005
    #14
  15. On Thu, 22 Sep 2005 14:02:56 +0200, in sci.electronics.design "
    Geocacher" <> wrote:

    >I work in the trailer manufacturing business.
    >We use LED tail-light clusters.
    >The modern truck/tractors utilise a computer system to perform diagnostics
    >on various systems within the rig. One of these is the lighting system.
    >A pulse is sent to each tail light, the system monitoring the current. If
    >there is current flow, it is assumed the incandescent globes are OK.
    >
    >Unfortunately, the LED lamps draw such a small amount of current that the
    >computer does not see a "filament" and flags a major fault on the truck
    >dashboard. In addition to the error message, the system continues to send
    >curent pulss in the forlorn hope that things at the rear of the rig have
    >improved. This causes the entire suite of LED lamps to flash like a
    >low-class disco!
    >
    >There are ways around it. Some manufacturers have placed incandescent globes
    >in parallel with the LED lamps, others have used high wattage resistors.
    >Neither is acceptable for obvious reasons.
    >
    >There must be a way to "tell" the computer that the LED lamps are fine by
    >emulating the current drawn by an incandescent globe, without using the
    >solutions noted above.
    >
    >Do any of you outstandingly brilliant contributors have any novel and
    >innovative ideas?????
    >

    Look up CAN bus, seems to be the indusrty standard. You need a micro
    in the LED array, that can talk to the vehicle


    martin
     
    martin griffith, Sep 22, 2005
    #15
  16. Geocacher

    Thomas Magma Guest

    Do you know what the old tail lights current draw is vs. the new LED ones?
    Is it 12VDC?

    " Geocacher" <> wrote in message
    news:dgv5p3$4qb$...
    > We cannot 'play' with the computer system aboard the truck/tractor, hence
    > this enquiry. The solution must be attached to the trailer wiring in such
    > a way that the truck's system is satisfied that the lights are functional.
    >
    > "Adrian Tuddenham" <> wrote in message
    > news:1h3azov.v9jsrl1ub1tbeN%...
    >> Geocacher <> wrote:
    >>
    >>> I work in the trailer manufacturing business.
    >>> We use LED tail-light clusters.
    >>> The modern truck/tractors utilise a computer system to perform
    >>> diagnostics
    >>> on various systems within the rig. One of these is the lighting system.
    >>> A pulse is sent to each tail light, the system monitoring the current.
    >>> If
    >>> there is current flow, it is assumed the incandescent globes are OK.
    >>>
    >>> Unfortunately, the LED lamps draw such a small amount of current that
    >>> the
    >>> computer does not see a "filament" and flags a major fault on the truck
    >>> dashboard. In addition to the error message, the system continues to
    >>> send
    >>> curent pulss in the forlorn hope that things at the rear of the rig have
    >>> improved. This causes the entire suite of LED lamps to flash like a
    >>> low-class disco!

    >> [...]
    >>>
    >>> Do any of you outstandingly brilliant contributors have any novel and
    >>> innovative ideas?????

    >>
    >> Get rid of the computer. It's probably less reliable than the LEDs
    >> anyway.
    >>
    >> --
    >> ~ Adrian Tuddenham ~
    >> (Remove the ".invalid"s and add ".co.uk" to reply)
    >> www.poppyrecords.co.uk

    >
    >
     
    Thomas Magma, Sep 22, 2005
    #16
  17. Geocacher

    Rich Grise Guest

    On Thu, 22 Sep 2005 22:55:23 +0200, Geocacher wrote:

    > We cannot 'play' with the computer system aboard the truck/tractor, hence
    > this enquiry. The solution must be attached to the trailer wiring in such a
    > way that the truck's system is satisfied that the lights are functional.


    Give each LED in the array its own dropping resistor, and run all of
    those LED/R strings in parallel. Use enough of them, at enough current,
    so the total current is over the threshold. LEDs _do_ take _some_
    current, you know. ;-)

    Good Luck!
    Rich
     
    Rich Grise, Sep 22, 2005
    #17
  18. Geocacher

    Genome Guest

    " Geocacher" <> wrote in message
    news:dgu6ht$g24$...

    Time for a nice cuddly sleep in my nice cuddly bed.

    DNA
     
    Genome, Sep 22, 2005
    #18
  19. Geocacher

    Thomas Magma Guest

    OK here is my "brilliant idea" of the day. A resistor that is in series
    with a polyfuse and then both in parallel with the LED lamp. This will shunt
    the appropriate amount of current to fool the computer into thinking it's
    drawing the right amount of current, then the polyfuse will trip before the
    resistor has time to heat up. The polyfuse will stay open until the voltage
    is removed. So you could probably get away with a small and cheap half watt
    resistor.

    Here is a link to polyfuses:
    http://wickman-fuses.com/download/ptcappnote.pdf

    Good luck.
    Thomas

    " Geocacher" <> wrote in message
    news:dgv5p3$4qb$...
    > We cannot 'play' with the computer system aboard the truck/tractor, hence
    > this enquiry. The solution must be attached to the trailer wiring in such
    > a way that the truck's system is satisfied that the lights are functional.
    >
    > "Adrian Tuddenham" <> wrote in message
    > news:1h3azov.v9jsrl1ub1tbeN%...
    >> Geocacher <> wrote:
    >>
    >>> I work in the trailer manufacturing business.
    >>> We use LED tail-light clusters.
    >>> The modern truck/tractors utilise a computer system to perform
    >>> diagnostics
    >>> on various systems within the rig. One of these is the lighting system.
    >>> A pulse is sent to each tail light, the system monitoring the current.
    >>> If
    >>> there is current flow, it is assumed the incandescent globes are OK.
    >>>
    >>> Unfortunately, the LED lamps draw such a small amount of current that
    >>> the
    >>> computer does not see a "filament" and flags a major fault on the truck
    >>> dashboard. In addition to the error message, the system continues to
    >>> send
    >>> curent pulss in the forlorn hope that things at the rear of the rig have
    >>> improved. This causes the entire suite of LED lamps to flash like a
    >>> low-class disco!

    >> [...]
    >>>
    >>> Do any of you outstandingly brilliant contributors have any novel and
    >>> innovative ideas?????

    >>
    >> Get rid of the computer. It's probably less reliable than the LEDs
    >> anyway.
    >>
    >> --
    >> ~ Adrian Tuddenham ~
    >> (Remove the ".invalid"s and add ".co.uk" to reply)
    >> www.poppyrecords.co.uk

    >
    >
     
    Thomas Magma, Sep 23, 2005
    #19
  20. " Geocacher" <> schreef in bericht
    news:dgu6ht$g24$...
    >I work in the trailer manufacturing business.
    > We use LED tail-light clusters.
    > The modern truck/tractors utilise a computer system to perform diagnostics
    > on various systems within the rig. One of these is the lighting system.
    > A pulse is sent to each tail light, the system monitoring the current. If
    > there is current flow, it is assumed the incandescent globes are OK.


    This is the place for some brillant questions. How often is that pulse send?
    How long does is last? What current does it expect? How much do the LEDs
    take? Is the voltage of that pulse the same as the normal operating voltage?
    Is that 12V or 24V or other? Is that pulse also send when the lights are on?

    > Unfortunately, the LED lamps draw such a small amount of current that the
    > computer does not see a "filament" and flags a major fault on the truck
    > dashboard. In addition to the error message, the system continues to send
    > curent pulss in the forlorn hope that things at the rear of the rig have
    > improved. This causes the entire suite of LED lamps to flash like a
    > low-class disco!


    Why can't you keep that lights on? Or do they continue to simulate that
    disco? What's the flash rate?

    > There are ways around it. Some manufacturers have placed incandescent
    > globes in parallel with the LED lamps, others have used high wattage
    > resistors. Neither is acceptable for obvious reasons.


    Why? I've done that kind of things some more times. It's obvious that the
    computer is to old to recognise the LED assemblies but apparently a
    modification of it - let alone a new one - is more expensive then the bulbs
    or resistors. I feel with you that it does not satisfy the technician but
    economics rules you know.

    > There must be a way to "tell" the computer that the LED lamps are fine by
    > emulating the current drawn by an incandescent globe, without using the
    > solutions noted above.


    Well, telling the computer requires a current high enough to make it think
    it sees incandescent bulbs. Bulbs or resistors come first into mind as you
    already know. You can circumvent it only if you have acces to the inside of
    the measuring system. It's almost sure that somewhere inside is a small
    resistor in the pulse circuit, used to measure the current by measuring the
    voltage accross it. If you can replace that resistor by a larger one, the
    voltage accross it will increase so the system will "see" more current.

    Another approach is to provide the bleeding resistor only when the computer
    sends the measuring pulse. That's why I asked so many questions above. When
    the pulse comes, the resistor is switched on by a transistor, a timer keeps
    it on as long as the pulse lasts and switches it of afterwards. It's some
    simple classical electronics once you know how to detect the start of that
    measuring pulse.

    > Do any of you outstandingly brilliant contributors have any novel and
    > innovative ideas?????


    Can't call that innovative. It's stretching the lifetime of an otherwise
    obsolete computer system. Can nevertheless be attractive.

    petrus bitbyter
     
    petrus bitbyter, Sep 23, 2005
    #20
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