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  1. #1
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    Lightbulb Electrical problem - why doesn't it work?

    Bought two B&M Lumotec OvalSenso (one of them is the Plus version with standlight) lamps, to go with my Schmidt hub generator.

    Both work perfectly fine when connected to the generator one at a time. But when I connect them in series, they don't light up at all. Not the tiniest flicker. Nothing! Also, the wheel spins the same way it does when there is no closed circuit - quite different from when there is a complete circuit.

    What is wrong?

    I've connected the wires like this (although not as neat, at least not yet):


    Both lamps are in the ON position - not sensor or off.

    They're electrically isolated from each other, apart from the wiring, of course.

    I'm really confused right now! Help!

  2. #2
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    Insufficient voltage, probably. Even though you have it set to constant-on, the internal electronics are probably still active, and causing the lamp to shut off because the lamp is only receiving half the voltage it's expecting. When you connect stuff like this in series the devices basically have to divide up the voltage. If the hub produces 6V, each lamp is only receiving 3V, which may be insufficient for either one to operate.

    You could try connecting them in parallel, which would send 6V to each lamp but only half the current. I don't know what effect this would have without knowing what the internal electronics actually do. Best case scenario they'd both work fine (and you'd be able to switch them on and off individually), worst case they'd be dim or not light.
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  3. #3
    Videre non videri
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    The Schmidt hub has no difficulty putting out 12 V, so that's not the problem. This is strange!

  4. #4
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    get a cheap multimeter and figure it out

  5. #5
    Senior Member kf5nd's Avatar
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    I know nothing about that hub generator... but what comes to mind is you've got a phase problem. Does that generator put out alternating current (AC)?

    Maybe your two generators are putting out AC waveforms with different phases (timing). And maybe they're cancelling each other out? Like when one puts out +5 volts, the other puts out -5 volts, and they sum to 0. But that's pretty odd that they would perfectly cancel each other all the time.

    But I'm guess they put out DC, but pulsed DC. But what would make the current pulsed DC instead of AC, which is what a generator does naturally? Some kind of rectifier circuit. Maybe the rectifier, sensing the current from the outside generator, is going screwball.

    Just conjecture.

  6. #6
    Banned. ModoVincere's Avatar
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    I do not know if you can hook up 2 of the Lumotec lights to the same generator.
    Peter White sells a Schmidt E6 and a Schmidt E6 Secondary that can both be hooked up to give you a lot of light, but the E6 Secondary has some special electronics built in that enable this functionality.
    http://www.peterwhitecycles.com/schm....asp#schmidte6

  7. #7
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    Quote Originally Posted by CdCf View Post
    The Schmidt hub has no difficulty putting out 12 V, so that's not the problem. This is strange!
    http://www.peterwhitecycles.com/schmidt.asp

    Scroll down to the section labeled "12 V SON." The hub produces 6V at about 5 or 6 mph (you are spinning the wheel that fast when you test it, right?), and produces more than that when you go faster. However, the lights have a built-in 6V regulator that prevents them from blowing up when you go really fast. Theoretically you'll have to be going 10-12mph to light both lamps to full brightness, but I assume you've tried this already, right?

    Again, try connecting the lights in parallel instead of in series.
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  8. #8
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    Parallel won't work. The current is constant, so if the hub puts out 6 V (as with a parallel wiring), it only puts out 3 W. That means each lamp only gets 1.5 W.

    It's not a matter of them not putting out enough light - there's NOTHING. Even if I only rolled along at 1 mph, there would still be a weak flicker. In this case, the bike is on a stand, and I spin the wheel by hand. I spin it hard enough for it to take half a minute to stop (which tells me that there is no load on the generator).

    And if you read this page, I've done what is described there (note that the lamps are connected in series in the article):
    http://www.peterwhitecycles.com/wiringinstructions.asp

    A few minutes ago, I took one of them off its mounting, and placed it on a shelf beside the bike, so that there could be no possibility of a ground between the two. Didn't help - still no light...

  9. #9
    Senior_Member2 diff_lock2's Avatar
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    You should get a multimeter, you could get real answers, like if there is voltage, or a short, of something from the factory messed up...

  10. #10
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    I have a multimeter. The only thing I can measure is resistance across each lamp, and across both lamps in series. Neither shows current flowing ("infinite" resistance), but since the lamps work fine separately, that's not much to go by.

    The only voltage comes from the generator, of course, and I've already explained that both lamps work perfectly fine when connected to the generator one at a time.

    There is no short (the lamps are separated by air and a dry cotton shirt only).

    I even tried connecting them to a stable DC source at 12 V, but still no light.

    Dual lamp setups are pretty common, so I expected more people to reply here. Perhaps this is a bad subforum for this - touring or long-distance cycling could be better.

  11. #11
    Senior_Member2 diff_lock2's Avatar
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    I think there are some internal electronics are cutting the curret after 6v. I think some one mentioned that already.

  12. #12
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    Well the Zener diodes are voltage limiters, as far as I can tell, but each resistor (i.e. bulb) out of the two in series shouldn't see more than half the voltage anyway, so that shouldn't be a problem.

  13. #13
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    Quote Originally Posted by CdCf View Post
    I have a multimeter. The only thing I can measure is resistance across each lamp, and across both lamps in series. Neither shows current flowing ("infinite" resistance), but since the lamps work fine separately, that's not much to go by.

    The only voltage comes from the generator, of course, and I've already explained that both lamps work perfectly fine when connected to the generator one at a time.
    Whoa, what? Do you have it set to ohms? With the wheel not spinning, you measure infinite (OL) ohms? There's your problem - you have an open circuit. You should be measuring something across both lamps at all times.

    To measure voltage across the lamps, you simply put one lead of the multimeter on each terminal of the lamp, or on each terminal of the hub. If you measure a voltage across the hub but nothing across the individual lamps, you have an open circuit. If you measure a voltage across the hub AND approximately half that voltage across each lamp then your wiring is OK and something else is wrong.

    Also, you can't measure current by placing the leads across the lamp terminals. This will cause the multimeter to blow a fuse. You have to break the chain and wire up the multimeter in series with the lamps to measure current. If you measure zero amps, then again you have an open circuit.
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  14. #14
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    Each lamp by itself works fine, and lights up (this tells us that both lamps work fine, and that the hub works fine as well). When I connect them in series (and the connection is good - I can measure a very low resistance across the connector), it doesn't work.

    I think the Zener diodes in the lamps may prevent my multimeter from getting a reading. It's powered by a single AA cell at 1.5 V only.

    I don't have enough hands to measure anything while the wheel is spinning...

  15. #15
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    Problem solved!

    I had incorrectly assumed that they were both electrically symmetrical, but the standlight function made one of them asymmetrical. Reversing the "polarity" of the leads solved it.

    Damn...

  16. #16
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    Quote Originally Posted by CdCf View Post
    Problem solved!

    I had incorrectly assumed that they were both electrically symmetrical, but the standlight function made one of them asymmetrical. Reversing the "polarity" of the leads solved it.

    Damn...
    Makes sense, a zener diode connected backwards will read open, thus preventing the series chain from working. Glad to hear you solved it!
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  17. #17
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    No, the Zener diodes are connected in both directions. It was the capacitor for the standlight that messed it all up, I think.

  18. #18
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    Quote Originally Posted by CdCf View Post
    No, the Zener diodes are connected in both directions. It was the capacitor for the standlight that messed it all up, I think.
    Ah, are they? Then yeah, it wouldn't have made a difference. A backwards polarized capacitor would have gummed up the works too, I'm just glad it didn't blow up...
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  19. #19
    Senior_Member2 diff_lock2's Avatar
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    I'm glad you solved the problem, this info will be very useful for the day i run dual b and m lights.

    Have taken it out for a ride? Beam and setup pics? Thanks

  20. #20
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    Quote Originally Posted by diff_lock2 View Post
    Have taken it out for a ride?
    Nope, it's not complete yet. This is my LHT built up in 2005. It's been through two salty and wet winters with no real care, so I finally decided to disassemble it and build it back up to be what it was intended to be - a long-distance machine.

    Right now, it has no rear brake cable, no bar tape, no crankset and no chain...

    Quote Originally Posted by diff_lock2 View Post
    Beam and setup pics? Thanks
    No beam pics (see above... ), and the setup is pretty simple. Two Lumotec Ovals about 1.5" apart, with the non-standlight one aimed slightly down.

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