pmanley

I am fitting some dynamo lights to my winter training bike. It is my first experience with dynamo lights and I am having a few teething problems. The equipment I am using is as follows: SON Dynamo hub, all lights are by Busch & Muller and all have a standing light that will keep running for a couple of minutes when the bike stops. The primary light is a B&M Lumotec Oval senso plus 6V 2.4W; the rear light is B&M Seculite plus LED; the secondary light is a B&M Lumotec LED Oval senso plus. The rear light is running off the primary light and works OK when the primary light works. I read on the internet that these lights tow headlight set-ups should be installed in series, so that is what I did. However, whichever way round I wire the series only one of the front lights works at any one time. If I wire in parallel both front lights work OK, but according to the experts this is not the way to do it. I have only tested these on the bike stand at about 16kmph or 10mph. Following my tests I have some questions hopefully there are some lighting experts out there who can assist me:

1. Why should the lights be in series and not parallel? I would have thought that parallel is preferable so that if one headlight fails the other will still run.

2. Why does only one of the two front lights come on when I wire them in series?

3. Does it matter which wire (black or black with white stripe) goes to which pole on the SON Dynamo hub? If not how do I know which light is acting as a primary?

4. Does it matter which way round the wires for the rear light are wired to the poles on the underside of the primary light.

Any suggestions or explanations would be gratefully appreciated.

InTheRain

Peter White Cycles has pretty good wiring instructions... I hope they help.

https://peterwhitecycles.com/wiringinstructions.asp

znomit

Check if the light is earthed to the bike. That will screw things up on light #2.

Michel Gagnon

You have two problems: the Lumotec Oval Senso Plus primary light and the Lumotec Oval Senso Plus secondary light. The problem isn't insurmountable, but you'll need to homebrew your own switch and wiring.... or change a headlight.


1. Primary Light
The Lumotec Oval Senso works with a taillight, so you're OK. However, the standlight function grounds the light to the frame, so to make it work with a secondary headlight, you need to insulate the secondary headlight from the bike. I'm aware that you can achieve such results by cutting a tab near the bolt – and some have successfully done it – but I'm weary of breaking those little parts and I'm not sure it would work anyway with a wired in taillight, unless it is also totally insulated.

2. Secondary headlight

The Lumotec Oval Senso Plus used as secondary headlight will have the same issue as above. You'll need to insulate it to make it work correctly. But there also is another problem.

The lights sold as "secondary headlight" have a different switch. The Lumotec Secondary (if still available) and the Schmidt E6-Z have a switch that actually shorts the headlight off the circuit when you turn it "off". In other words, even if you wire correctly both of your headlights (see Peter White's website), you will only have the lights work when both of them are ON.

Solutions
a. Install your secondary headlight on an insulating bracket (ex.: plastic bracket). You have to do that even if you use a different secondary headlight.
b. Follow Peter White's wiring instructions.
c. Either replace your "secondary" with a properly designed secondary headlight, or keep the second headlight on at all times. If you want better lighting at low speed (i.e. lower than 18 km/h), wire your own switch as a bypass switch.
d. Your second headlight is not wired with a taillight, so it absolutely needs to have a 3 W bulb in it. Otherwise, you'll burn the bulb very quickly.

pmanley

I managed to get both lights working by isolating one from the other. It looks to me like I have two options now:

1. Buy another R&M mounting bracket €11.00 for a single lamp to isolate and continue to use the lights I have already bought. I would also adapt the double bracket to fit one light only. This option means that both lights will be on or off, I have no single light option. Not a big problem but if one fails they both fail.

2. Buy a SON-E6-z headlight, with 3w bulb & bypass switch for use in dual (12v) installations for €75.00.

Question: Will this (option 2 above) work OK on the double R&M mounting or will I still have to isolate the lights from each other?

brotherdan

I would go with the first option. Wire the lights in series and make sure that they are insulated from the frame on separate mounting brackets. Make sure that the wire running from the secondary light to the hub is longer than it needs to be, so if the secondary light fails you can connect the ground wire directly to the primary light and run on just one headlight. If the primary light fails, you can do the same thing, but you would have to take the bulb out of the secondary light and put it into the primary light (and you would have to be careful not to directly touch the bulb when transferring it, because contact with your skin would destroy a halogen bulb). But this would save you a lot of money.

diff_lock2

I do not understand why wiring halogen lights to a dynamo is made imposible.

The OP is not the first person with problems running two headlights at once.

I think is it has somthing to do with the protection diodes thing inside each light.

I would also expect that running the 2 lights off the dynamo in parralel is better.

Michel Gagnon

For Peter:

– Whatever option you select, you'll need to isolate the light. I don't have an E6-Z to check, but the E6 (primary) is not insulated in itself, therefore you'll need to do so. Apart from another "R&M Mounting Bracket" (hope it's insulated, as I have not seen its specs), you could use a piece of bakelite or plastic EMT conduit. This is basically what you would see around the centre point of this page.

– Whether or not option 1 is liveable is up to you. Apart from the "no backup light available", it means you have a workable light when you ride fast, but not when you crawl. So that's fine if you ride on flat terrain, train for the Tour de France, etc. but not if you like gentle strolls, low-speed climbs, etc.

– To save some money and still get the 1/2 light option, you could install your own switch on the circuit. Basically look at the 12-Volt page on SON's website (bild 3) and install your own switch on the circuit. But you must get a 3-W bulb in it.


For DiffLock 2:

The problem Peter has lies mostly with the complex circuitry around the standlight feature.

The lights must indeed be mounted in series, not in parallel. The generator provides a constant 0,5 A, whatever the travelled speed. So the faster one rides, the higher the voltage becomes. With the SON, one gets (from memory) 6 V at 10 km/h, 12 V at 22 km/h, 20 V at 45-50 km/h, etc... but all the time at 0,5 A.
With a single headlight, all that extra voltage is lost by the zener diode when one rides "too fast" for the light. A double headlight – in series – increases the output, and likewise a 3rd headlight in series would provide light when one travels at 35 km/h, etc.

pmanley

I have decided to carry out three changes to fix my problem:

1. Mounting the two front lights on seperate brackets so that they are isolated from each other.
2. Buy an E6-Z as my secondary light.
3. Use the LED front light as my primary with the back light attached to this one.

Hope this work. I'll post here about how I get on with these changes. Thanks to all above for their advise.

pmanley

I have mounted the front lights on seperate plastic brackets. I am now using:
- primary light is the B&M Lumotec LED Oval senso plus
- secondary light is E6-Z
- rear light is a B&M Seculite plus LED
This system works great - no problems so far. The most dificulf thing was cutting away the plastic mounting brackets so that they would fit on my oversized handle bars. My advise to those who like me have no experience with lights is - buy a secondary light that is designed to be a secondary light - don't try to save money using a regular light (like I tried to do).

Note: after I had bought the E6-Z I was told told that they will be bringing out an LED version of the E6-Z secondary light soon.

Thanks to all for your help.