exarkuhn15

Hi everyone,

I have a Shimano dynamo hub wheel with a Planet Bike Blaze dynamo headlight. The headlight is fantastic, incredibly bright, and makes a great daytime running light.

However, the problem with it is that it is not designed to work with a rear dynamo taillight.

I own a rear dynamo taillight, and a front Spanninga headlight that can work with a rear taillight.

Does anyone know of a wiring schematic such that I could use both front LED dynamo headlights, and the rear taillight? I am thinking that I would bring the front Spanninga light in so that I can use the rear light, and then somehow connect the Planet Bike Blaze Dynamo to the front Spanninga and/or dynamohub so that it doesn't go to waste. Remember, the problem is that the Planet Bike Light does not have the taillight connections that a normal dynamo front light would have.

I don't know much about wiring, so I would like to know exactly what to connect to what!

Any suggestions? Thanks!

zebede

Connect the both the positive wires from the two lights to the positive terminal of the generator.
Connect both of the negative wires from the two lights to the negative terminal of the generator.
The two lights will be sharing the output of the generator. I believe this would be called running in parallel.

I have the PB Blaze and have it wired this way, but my second device is not a light but a USB converter charger. When I turn off the PB Blaze, the USB converter receives all of the output from the generator.

fietsbob

ZBD is describing a parallel wiring scheme..

I have the 1w planet bike battery version (the dynamo version is also 1w) on my Bike..

the hub powers a second headlight, mine is by the fork crown, the taillight is wired to the headlight.


IDK if the dynamo super flash has a standlight (capacitor) or it goes out when you stop.
anyone that owns one, speak up ..

noglider 

Even though I often say how I think dynamo lights make more sense than battery lights, I think battery tail lights are fine. Tail lights require a lot less power than headlights, so they don't need battery replacement frequently. So a simple solution for you is to keep your headlight and just add a battery powered tail light.

savvas

Ancient thread I know but I think it's worth pointing out that bike 'hub generators' or hub dynamos - unlike sidewall dynamos - do not have positive and negative terminals. They produce alternating current - AC - which, when applied to LED lights, is bridge rectified by the lighting system and then fed to the LEDs. So it doesn't matter which way round you connect the headlight wires to the dynamo!

Current headlights made by SON, B&M, Spanninga (the Axendo based on the Phillips design) and similar, all have internal rectification/regulator circuits which ensure their internal LEDs are fed current with the correct polarity.

The external connections on most of these headlights (maybe not the Supernova) all provide access to alternating current from the dynamo. It may help to remember that B&M tail lights and most similar lights from other manufacturers are made for markets where millions of bikes still tend to use incandescent bulbs (remember them?) which are polarity-agnostic.

So virtually all B&M tail lights and similar have their own rectification circuits inside so they can deal with alternating current. Although they are marked +ve & -ve (in a nod to those millions of bikes still using sidewall generators) it doesn't matter which way around they are connected to the head light's terminals.

Tourist in MSN

I am pretty sure that my old Union brand sidewall unit put out AC.

znomit

One of the connectors is often grounded (on both the hub and light)so you might end up shorting the dynamo hub if you aren’t consistent with your wiring.

savvas

Thanks - yes, I now realise that you are correct. I guess the point I was making that the raw current is AC and the connection points at the generator are not polarised. LED headlight units therefore have their own internal rectification and don't mind which way around their wires are connected to the generator. Same for most LED tail lights (with caveats in mind for the Supernova lights). Incandescent headlights and tail lights will of course happily run on either AC or DC...

savvas

Hi Znomit - nice to see you are still around (BikeCurrent days??)

I can't recall which generators and headlights are grounded and which are not but I doubt that the PB Blaze (with its plastic case) is. Most rack-mounted tail lights that I've seen have the mounting bolts insulated from the circuit so either require 2 wires or grounding one terminal to the rack somewhere. Different for mudguard mounted lights (such as the B&M Pixeo) perhaps....

For those interested Peter White Cycles still has excellent product-specific reference info posted at his site on all of this stuff!

Tourist in MSN

Shimano dynohubs are grounded to the fork, at least the Shimano that I have is. SP is not. I do not know about Son.

I think that Son also has an odd sort of hub that is designed so that both connections are through a special fork without wiring from the hub, but if you had that I am sure you would know it.

znomit

Yes, that's an incredibly tidy solution, no visible wiring down the fork. When I win the lottery....
https://nabendynamo.de/en/products/sl/

Savvas you are right that most light setups won't care about polarity, but every now and then someone can't get their taillight to work for no apparent reason...

unterhausen

Usually running the wires backwards only causes problems with a taillight. I think it's best to stick to the way they intended for you to wire it, because troubleshooting can be annoying. If you could find all the dyno troubleshooting threads here and elsewhere, I think this is by far the most common issue.