Whelen TIR 3: isolate from LED taillights?

Discussion in 'The Garage' started by markgsnw, Feb 2, 2014.

  1. markgsnw

    markgsnw WTF?

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    Years ago I added a Whelen TIR3 to my GS, loved the thing. Recently decided to add one to the Norge, bracket is done and most of the wiring. What I think I'm learning from my voltmeter is the the brake light circuit is being fed a constant 7 volts, and gets fed 13 volts when the brakes are on. Poking around here, that appears to be the case with other bikes with LED tail/brake lights. I don't want the TIR3 to be on all of the time, only when I'm braking, so...



    I'm wondering if I can use a 12 volt relay to isolate the LED brake lights from the TIR3's. If I'm reading the specs correctly for a Bosch relay, the pull-in voltage is 8 volts, and the drop out voltage is 1.2-5 volts, which in this case wouldn't do anything for me.



    My electronics engineering experience is so far in the past that I've forgotten much of it. Can any of you electrical/electronics whizzes think of a way to isolate the TIR3 so that the TIR3 is only on when the brakes are applied?
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  2. markgsnw

    markgsnw WTF?

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    I'm thinking I can use a diode in the relay power circuit. I'll read up and report back.
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  3. ttpete

    ttpete Rectum Non Bustibus

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    Sounds like you might have a Canbus electrical system. If it is, one of the BMW guys might be able to advise you.
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  4. markgsnw

    markgsnw WTF?

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    Not a canbus
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  5. ttpete

    ttpete Rectum Non Bustibus

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  6. markgsnw

    markgsnw WTF?

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    Not a canbus, but that link is solid gold. Blocking diode is what I had in mind and it is mentioned there as well. Thanks!
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  7. Jedi Apprentice

    Jedi Apprentice Been here awhile

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    Im putting a whelen on my bike as well this winter- any install pics? How much do people complain when you lead group rides?
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  8. Bbasso

    Bbasso my name is Rob

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    Seems odd that one wire is feeding two signals to your light.
    Example, my Honda has a three wire system for brake, tail and ground.

    Are you sure that you are checking the correct wiring... and such?
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  9. troidus

    troidus Long timer

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    Having a single emitter (array) perform two functions by varying the voltage or pulse width is becoming more common.
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  10. Bbasso

    Bbasso my name is Rob

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    I guess I'm getting old...
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  11. tick-tock

    tick-tock Adventurer

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    QUOTE=troidus;23385656]Having a single emitter (array) perform two functions by varying the voltage or pulse width is becoming more common.[/QUOTE]

    Dang. That makes adding a brake flasher so much more complicated than it used to be. I'm interested to hear what you come up with as a solution. The relay seems like a good idea.
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  12. riverflow

    riverflow Adventurous Commuter

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    I think the simplest thing would probably to also wire the TIR 3's would be to wire them in with the switch. However, at the back end I have an idea of a mechanism and could probably come up with the numbers you need.

    You have your brake lights as is right now, and in parallel run a high resistance circuit to trip a solenoid. You can splice this back inline and run another pair of parallel circuits with your regular brake light on one and the TIR 3 on another line passing through the solenoid.
    If you get the resistance right, the solenoid will only open and illuminate the TIR 3's when you have the full voltage applied.

    If you want I can draw it out and calculate what numbers/parts you need.

    Edit: This is assuming that you only have one hot line and one ground running to the taillight.
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  13. markgsnw

    markgsnw WTF?

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    My recollection is that parallel circuits have the same voltage. Kirchhoff's Law.
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  14. LexLeroy

    LexLeroy Chief Mansplainer

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    Whelen LIN3 wired in parallel with my DL1000's brake filament - no high-tech CANBUS stuff goin' on in Suzuki-land.

    [​IMG]

    The Whelen LIN/TIR light heads are EXTREMELY bright and irritating so I wired mine w/ a QD plug under the seat so that I can kill it for group rides. Oh, to add to the irritation quotient mine is wired through a Comagination brake light modulator so that it flashes a few times before it stays full on. (He he he he.)
    #14
  15. riverflow

    riverflow Adventurous Commuter

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    Well, yes, but the line with the resistor in it would not allow enough current to flow to open the solenoid until the high voltage brake light came on. Ohm's Law.
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  16. markgsnw

    markgsnw WTF?

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    here's what I believe will work:




    Feed from brake light switch-----------|>|------------LED Brake Lights
    |
    |
    |
    |-----------------------TIR 3




    The diode blocks the 6 volt feedback from the LED cluster. The TIR3 gets either 0 volts or 13 volts, which is desirable. No relay required.
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  17. StopnExsanguination

    StopnExsanguination Regularly Irregular

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  18. ghostrider.y2k

    ghostrider.y2k ride enything but HD

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    I run Nova strobe hooked up to brake light leed, when bike is on work as a extra tail light but when brakes applied will strobe one of 8 flash patterns.

    [​IMG]

    On Maggie's bike we run two 3/4" strobe lights, when brakes applied it will strobe 3 series of 3 flashes and stay solid red.
    Nice and small, we noticed that "phone booths" keep the distance behind us.

    [​IMG]
    #18
  19. markgsnw

    markgsnw WTF?

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    here's what I think I know about having a LED tail/brake light cluster:


    A conventional incandescent setup has two bulbs (or a single bulb with two filaments), so that the brake light circuit is entirely separate from the tail light.


    The LED array is, essentially, a single circuit, or a single "filament". Six volts is sent to it all the time to create tail lighting, and 13 volts is sent to it to create brake lighting.


    In order to add an additional discreet brake light, we somehow have to mask or block the six volts from the new device. One way to do that is to use the diode in the sketch above. A diode is a one way valve, so that the 13 volts from the brake light switch pass though it, and the six volts that are always present are blocked. It's a fairly simple and inexpensive solution (diodes run about five cents each), the down side is that it involves cutting the brake light wire.


    Hope that helps with the collective knowledge.
    #19
  20. James Adams

    James Adams ɹǝsn uʍop ǝpᴉsdn Administrator

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    It's probably not really six volts, just a PWM signal at ~50% so it looks like 6V in a basic DC voltmeter. But the circuit with the diode should work fine.

    Alternatively, you can use a trailer light converter designed to take that PWM signal that is being sent to the taillight and "decode" it for a basic flat-4 trailer connector. This could be put to use to isolate the brake light and power the Whelen.

    Something like this.
    #20