1987

It says in the instructions for Busch + Müller IQ-XS T Senso Plus Front Light that the long cable should be connected to the dynamo and the short cable (via extension) to the rear lights. Does this really electronically matter or is it just how the manufacturer prefers the cables to be connected?


Same image on Imgur: https://i.imgur.com/LrZ1Tei.png

Data and sources
Front: Busch + Müller IQ-XS T Senso Plus Front Light - 167RTSNDI - silver
https://www.bumm.de/en/products/dyna...di-silber.html
https://www.bumm.de/files/Produkte/L..._Avy_IQ-XS.PDF

Rear: Busch + Müller Seculite Plus LED Rear Light - 330ALK

Tourist in MSN

I do not know, but I did it the way they said to on two of my IQ-XS lights, it worked fine. I had no reason to try something else.

unterhausen

The lights are complex enough inside that it seems likely that they limit the current to the rear lights. So wiring it their way is probably a good idea.

1987

Thanks for your input Tourist in MSN and unterhausen
Yes, these modern LED lights has much more electronics inside than the old with filament bulbs and might thus be sensitive how they are connected.

Tourist in MSN

If you are curious, I described how I wired up one of my bikes here:
https://www.bikeforums.net/electroni...b-charger.html

ThermionicScott 

My understanding is that the dynohub is outputting AC, the B&M headlight contains a rectifier and it is putting out DC for the taillight (and other accessories), so it's vital to use the correct connections. I'll invoke Cunningham's Law if this is not the case.

unterhausen

I thought that some B&M taillights can run directly off of the dyno, but Peter J. White says no.

Tourist in MSN

I had to look up Cunninghams law. Thanks. I will try to remember that. The only flaw is that there are several on this forum that frequently say "You are wrong" when you are not wrong.

The hub puts out AC. The electronics in the light require DC, thus a rectifier. I believe that there is also a rectifier in the taillight, thus a taillight can run on AC.

BUT, it can get complicated, as the headlamp unit has overvoltage protection, the taillight typically does not. So, you wire the hub to the headlamp. The taillight gets wired to the headlamp and the headlamp provides the overvoltage protection for the taillight.

When the headlight is switched off, both lights are off and consume no power. (I do not know if the headlamp standlight capacitor will charge with the light switch off or not, if it does, it could consume some power.)

So, things can get complicated.

The Luxos U is a different light, some of what I said above is not the case. And Supernova lights are different and the above might not be correct.

This is the simple version, I did not mention grounding to the frame or fork.

unterhausen

What's different about the Luxos? After hearing about all the failures, my Luxos has been sitting in a box.

Supernova taillights are very simple and probably will fail early if not attached to a Supernova headlight. I had one warrantied, and the one I got as a replacement is really bright. Can't say the same about the headlight, which is disappointing.
The difference in size between the Supernova headlight with a switch and without a switch makes me wonder how much circuitry it really takes to monitor a switch. I never turn my lights off, so the switch is just an extra failure point.

Tourist in MSN

Luxos U, differences from what I wrote:

• It has an internal Li Ion cache battery to power the USB port. Thus, it will consume power when the light is turned off.
• I recall reading somewhere that the B&M taillight that also had a brake light, that brake light read the frequency of the AC current and when the frequency quickly dropped, it knew your hub was rapidly slowing and would light the brake light. And either early versions of the taillight or early versions of the Luxos U did not play well together. But, I think later versions got the incompatability fixed.
• I have also read that if your taillight is grounded to the frame, the Luxos U might have a problem with it, but since the Luxos U is not grounded to the frame, I do not understand why that could be a problem.

We have both read about problems with rain and the Luxos U. I have been careful to not mix rain with my Luxos U lights (I have 2). And I am a fair weather brevet rider only, forecast for a rainy day and I stay home. And, I have the IQ-XS on my rando bike, not the Luxos U.

One of my Luxos U lights, the on/off switch on the back of the light housing no longer works, but the handlebar switch continues to work.

On a different thread on this forum in the past few months, someone pointed out that you could buy an aftermarket generic handlebar switch for motorcycles. Such a switch, if you needed it for a light should be easy to wire into the wires to the light. I had a very minimalist high/low beam switch on one of my vintage Triumph motorcycles. Rain had no effect on it.

unterhausen

Thanks, I forgot all that about the luxos.

The Luxos has circuitry to see if all the current going to the taillight was coming back, like a gfci in house wiring. Some taillights are grounded to the frame, so not all the current goes back to the headlight. They fixed the taillights. I modified the one I used with it to cut the connection to the frame after Peter White told everyone about the issue.

The problem with the switch was most commonly at the connector at the headlight casing, I think. Fairly soon after they introduced it, they started hard-wiring the switch to the light. If I start using it again, I will just not use the switch and fill the connector with sealant. I tried using the USB and it never was very useful for me.

steelbikeguy

I fixed a very dead Supernova Triple a few years back. I had to reverse engineer most of it, and my recollection is that the tail light was just three red LEDs wired in series. The headlight provided a regulated current and standlight power. This is very different from B&M and probably every other light manufacturer.
As with everything, the design may have changed since then. Still... it seems like a bad idea to try to connect a Supernova tail light to a headlight from another manufacturer.

Steve in Peoria

Tourist in MSN

Peter White website is quite clear on problems with mixing Supernova parts with other brand parts.

I just avoid buying anything of that brand, that way everything I have generally plays well with each other.

I have a couple Spanninga Pixeo taillights in current use, in storage I have an AXA headlamp, other than that I have a lot of B&M headlamps and a few taillamps. And I have no B&M brake lights, so no worries about using my Luxos U headlamps with any of my taillights.

unterhausen

I recall they had some surface mount resistors in the taillights, but I have only seen pictures on the internet. "Fail quickly" is my way of saying it's a bad idea.
I had an E3 fail under warranty. The back cover had started unscrewing itself, so it was pretty simple to take the back cover off and pull the guts out before I sent it back. It was far more complex than I thought it would be, it's so big because it's full of tiny surface mount electronics. I'm impressed you could fix it. I had a second one on my gravel bike, but now that I think of it I didn't have a dyno taillight on that bike. That light is now in a box and I have a B&M in its place. So taillights are easier.

On edit: Now there is an edelux version of the Luxos: https://nabendynamo.de/edelux-ladescheinwerfer/
I'll let someone else experiment with it, I'm sure some randonneurs will buy it.

Tourist in MSN

That is a lot of claimed power output. There is a USB charger powered by dynohubs that can put out a lot of power, I think Forumslader is the name. A few on the touring board have played around with it. One said that when it was tasked with putting out high amperage, the bike felt slower.

I have have developed a preference to a USB charger that is separate from the light. When I go on a bike tour on an airplane with my S&S coupled bike, I no longer bring dyno powered lights, instead the hub is only used for USB power for batteries. I bought a Cycle2Charge V3 last summer, that is a dynohub powered USB power source that worked pretty good at keeping all my electronics powered on a two week tour this past spring.

steelbikeguy

The Supernova Triple that I repaired had surface mount parts, but the IC's were labeled and very common parts. The owner had hooked it up to an e-bike and blew up just about all of the semiconductors. It was a fun puzzle to reverse engineer the light. I never did figure out a section that varied the duty cycle of the buck converter as a function of the dynamo voltage.... at least in terms of what it was trying to do.
Reviewing the schematic, I see that it just used a LM317L to drive the tail light with a regulated voltage, which really doesn't make sense.
Here's the board with my own reference designators for the components:



For comparison, I've got a dead B&M Eyc that I've been meaning to reverse engineer. Might be able to fix it, or might be able to drive the LED with my own electronics. It certainly appears to be based on a micro-controller controlling a buck converter. None of the semiconductors have any markings, so it would take some work to figure out all of the connections and then guess at what is going on.





Steve in Peoria (with some other circuits that need attention too. )