Power two taillights with one dynamo?

[mickeg]

Many headlight units have a place to plug the taillight connectors into.  Check your instructions and if it includes instructions on wiring both lights, follow the instructions.

The only time you would want to run any lights in series is if they both use the same amount of current. 

My two headlight setup is an example, both headlights are the same model so have exactly identical requirements.  And my taillight is battery powered, so that simplifies it when only my headlights are in the circuit.

But a headlight and taillight will have different current requirements, I would not be surprised if attempting that in series damaged something.

[Danneaux]

One important point to note wrt LED dynamo lighting:

LEDs require DC voltage, and most LED taillights lack a rectifier of their own and so depend on a circuit in the headlight to convert AC to DC for proper operation. My tests show not all (i.e. "few" or "no") LED taillights have voltage limiters, so also depend on the headlight for that.

Best,

Dan.

[martinf]

LEDs require DC voltage, and most LED taillights lack a rectifier of their own and so depend on a circuit in the headlight

I suppose most B&M tail lamps must be an exception then.

I still have B&M Seculites on 2 bikes and one of the older B&M Toplights on 1 bike, connected directly to bottle dynamos in parallel with LED front lamps. I had similar systems on nearly all family bikes before I started using hub generators, initially with front halogen/rear LED before front LED lamps became available.

I never had any problems with the LED tail lamps, even if used for a few kms with a failed (halogen) front lamp (which is probably not recommended).
Going further back in time, rear lamps with filament bulbs would burn out almost immediately if the front lamp failed.

[Danneaux]

I suppose most B&M tail lamps must be an exception then.

That could well be, Martin. I wonder if it is all of them? When I mounted a B&M Line Plus on my SON28-equipped Extrawheel trailer, I was unable to get it to work until I designed and built a voltage rectifier/limiter for it. It worked fine, then.

I still have B&M Seculites on 2 bikes and one of the older B&M Toplights on 1 bike, connected directly to bottle dynamos in parallel with LED front lamps.

I don't doubt it for a moment, I just wish there was a way of determining for sure in advance of purchase. I wrote B&M and asked, and was advised to wire the taillight directly to the headlight -- only. I do know the model with the brake-light function requires different wiring from others, and some of B&M's models initially did not play well with the Luxos headlight. Perhaps they vary from model to model or perhaps they change from time to time in production?

Going further back in time, rear lamps with filament bulbs would burn out almost immediately if the front lamp failed.

<nods vigorously> Boy! I'll say; mine lasted about a nanosecond after the headlights blew, back in the days when I used filament bulbs.

Best,

Dan.

[il padrone]

But a headlight and taillight will have different current requirements, I would not be surprised if attempting that in series damaged something.

We have run B&M Cyo and Seculite in series with no adverse effects. The lights both ran at expected outputs. Having said that it is not ideal as should one light fail the whole lot is out of action.

[il padrone]

I suppose most B&M tail lamps must be an exception then.

I still have B&M Seculites on 2 bikes and one of the older B&M Toplights on 1 bike, connected directly to bottle dynamos in parallel with LED front lamps.

+1

[RonS]

Well, I finally got around to trying out the Secula/Toplight combo along with my Cyo headlight. I had given the light to my daughter to test as the dynamo was on her bike at the time. 21 year old ladies are not really too keen on doing experiments for dad though, so the light got "misplaced" under whatever was heaped in her dorm.
Now that the dynamo wheel and lights are now on the Raven, I can say that there is plenty of juice from the dynamo to power everything. I tried running one tail light and two and can't tell any difference in light output. The lights are wired in parallel, using the tail light output wires on the headlight.

[Danneaux]

I can say that there is plenty of juice from the dynamo to power everything. I tried running one tail light and two and can't tell any difference in light output. The lights are wired in parallel, using the tail light output wires on the headlight.

Thanks for checking back in with the firsthand report and update, Ron; I'm sure this will prove helpful to others in the future.

Best,

Dan.

[Aushiker]

Now that the dynamo wheel and lights are now on the Raven, I can say that there is plenty of juice from the dynamo to power everything. I tried running one tail light and two and can't tell any difference in light output. The lights are wired in parallel, using the tail light output wires on the headlight.

Thanks for the update. I am still to get mine setup. Small  problem my wheel building skills has delayed things somewhat

Andrew

[Andre Jute]

Now that the dynamo wheel and lights are now on the Raven, I can say that there is plenty of juice from the dynamo to power everything. I tried running one tail light and two and can't tell any difference in light output. The lights are wired in parallel, using the tail light output wires on the headlight.

Thanks for that, Ron.

It sounds like you have two taillights in parallel, the pair in series to the headlamp. Your remark about "plenty of juice" raises the further question:

How much current would a SON actually produce if loaded up with enough devices (lamps, GPS being recharged, etc) to keep the voltage down to 6V at the first LED.

And another question:

Presuming rectification but no regulator circuit in the lamp (neither of which we know for a fact), if the load was enough to bring the voltage down to 5V, would the LEDs still work, and how effectively?

[Danneaux]

Peter White has shed a bit more light (sorry!) on the matter of multiple dyno-powered LED *head*lights here: http://www.peterwhitecycles.com/wiringinstructions.asp

CYO, Edelux and Supernova E3/E3Pro headlights can all be "doubled up", You can use two CYOs, two Edelux or two Supernova E3. But don't mix and match between brands. That hasn't been tested.

Best,

Dan. (...who bemoans the apparent discontinuation of the dual-light version of Thorn's alloy mounting bracket, now available only as a "single": http://www.sjscycles.co.uk/thorn-alloy-dynamo-headlamp-bracket-m5-fork-crown-mounting-black-prod12373/?geoc=us )

[mickeg]

I usually make my own light brackets anyway.  A bit of strap Aluminum, a drill, some drill bits and an M5 or M6 tap is all it takes.  Sometimes I get fancy and spray on some matt black primer when done.

I sometimes run a single Lumotec oval, sometimes a double setup.  In both cases I am using home made brackets.

[RonS]

Presuming rectification but no regulator circuit in the lamp (neither of which we know for a fact), if the load was enough to bring the voltage down to 5V, would the LEDs still work, and how effectively?

While I was tidying up the wiring  today I did a low tech test. Poke the probe wires from my multimeter into the back of the connectors for the wires going to the tail lamps and give the wheel a spin. I got just over 6V AC, so, in the Cyo at least, there is no rectification in the output to the tail lamp. I didn't spin the wheel fast enough to to see how many volts I could get. I'll have to get some alligator clips for that test. All in the name of science.

[Andre Jute]

While I was tidying up the wiring  today I did a low tech test. Poke the probe wires from my multimeter into the back of the connectors for the wires going to the tail lamps and give the wheel a spin. I got just over 6V AC, so, in the Cyo at least, there is no rectification in the output to the tail lamp. I didn't spin the wheel fast enough to to see how many volts I could get. I'll have to get some alligator clips for that test. All in the name of science.

It proves, though, that your two rear lamps are not overloading the hub dynamo, even at modest speed.

[sd]

One important point to note wrt LED dynamo lighting:

LEDs require DC voltage, and most LED taillights lack a rectifier of their own and so depend on a circuit in the headlight to convert AC to DC for proper operation. My tests show not all (i.e. "few" or "no") LED taillights have voltage limiters, so also depend on the headlight for that.

Best,

Dan.

Nicelite bulbs can run anywhere between 1.5 volts to 9volts and always be the same brightness. Fitting batteries the other day the light takes 4 but light will work on 2. So appeared to be normal brightness at 1.2 volts