Axa bottle dynamo wiring

[Bob999]

Good evening

I wonder if someone could advise me about Axa bottle dynamo wiring please. I find electricity a difficult phenomenon to understand, to be honest. The Axa HR Traction states it has an 'overvoltage diode'. It also has two sets of connectors. Does that combination mean I can take a wire directly to a rear LED without a risk of it blowing? It seems like it should but I don't feel confident about it.

Thanks for any help.

[mjr]

Yes, I think I wired directly to my rear and didn't blow, but it's been a few years since I used it.

[rjb]

Yes and no. I would only feel confident if the rear led has protection built in against excess current and voltage. Older rear LEDs may not be protected.
Having a single diode, probably a zener diode may only limit the voltage on half the AC waveform. Riders would often use a pair of zener diodes connected back to back across the dynamo output to limit the overvoltage.
This link to a diy site has lots of useful information. http://www.pilom.com/BicycleElectronics ... rcuits.htm

[rjb]

In that link I posted above they opened up an AXA HR dynamo and it had 2 zener diodes within so it may well be protected against overvoltage, so it may be suitable for running a rear led only.
http://www.pilom.com/BicycleElectronics/Dynamo.htm

[andrew_s]

Almost all LED dynamo lights are fine to attach directly to the dynamo.
There's a Supernova rear light that piggybacks off the rectification and standlight supply in the front light electronics, but that's all I can think of that won't.

The overvoltage protection in the Axa HR is there to cope with old-style filament bulb lights, where, without the protection, a blown bulb in the front light would more or less instantly also blow the bulb in the rear light.

[deeferdonk]

All the front dynamo lights i have had for both bottle and hub dynamos have had wires/connection points for a rear light so i have always run connection from dynamo to front light to rear light.

I'm presuming your circumstances/preferences are different - but would be interesting to understand the background. (sorry just being curious/nosy!)

[Carlton green]

I wonder if someone could advise me about Axa bottle dynamo wiring please. I find electricity a difficult phenomenon to understand, to be honest. The Axa HR Traction states it has an 'overvoltage diode'. It also has two sets of connectors. Does that combination mean I can take a wire directly to a rear LED without a risk of it blowing? It seems like it should but I don't feel confident about it.

As far as I know both front lights and dynamos have had over voltage protection built into them for decades - probably to comply with some German specifications. I’ve also never heard of someone blowing an LED and really aren’t sure that that’s possible.

All of the dynamos that I use have only one ‘set’ of terminals and that has never been an issue; two sets of terminals could be a helpful convenience, but it’s a convenience that’s simple and easy to manage without.

I wire directly to the rear LED, it’s never been an issue.

Some modern front lights have connection terminals for rear lights, traditionally that wasn’t the case and the cheaper - but perfectly adequate - front lights that I have on my bikes don’t offer that facility.

[andrew_s]

All the front dynamo lights i have had for both bottle and hub dynamos have had wires/connection points for a rear light so i have always run connection from dynamo to front light to rear light.

Recent front lights are designed for use with hub dynamos, and have rear light connections so that the rear light can be turned off using the switch on the front light.
If a rear light is connected directly to a hub dynamo, you've got to disconnect the wires to turn it off.

With a bottle dynamo, it doesn't really matter where the rear light is connected.
It's best to try to remember that there is a front light switch, even if you never use it, in case some helpful soul tries to use it to turn your standlight off, and leaves it set to off (DAHIKT).

[mjr]

All the front dynamo lights i have had for both bottle and hub dynamos have had wires/connection points for a rear light so i have always run connection from dynamo to front light to rear light.

Recent front lights are designed for use with hub dynamos, and have rear light connections so that the rear light can be turned off using the switch on the front light.
If a rear light is connected directly to a hub dynamo, you've got to disconnect the wires to turn it off.

I don't think it's as simple as old/recent. For example, current Axa lights are a jumble, with some having connections for a rear light and others not.

Because the on-lamp switches seem to often be a failure point, and some lamps don't have them at all, I have a motorcycle headlight handlebar switch wired into the circuit!

[Bob999]

Many thanks to everyone for the replies, all really helpful.

I haven't got the lights yet, so that is why I was asking really. Bottle dynamo + niceish LED lights is I think the best combination in affordability for me. The bottle vs hub threads on this site are very interesting, I hope the 'pro-bottle' experiences are right!

[Carlton green]

Many thanks to everyone for the replies, all really helpful.

I haven't got the lights yet, so that is why I was asking really. Bottle dynamo + niceish LED lights is I think the best combination in affordability for me. The bottle vs hub threads on this site are very interesting, I hope the 'pro-bottle' experiences are right!

Those that like bottles seem to be in the minority here. As it happens I used my bottle dynamo this evening, a short ride back from the shops in the dusk.

If expense is no matter then hub dynamos are arguably better in use than bottles are, but I’m tight and for my use the extra expense and messing about simply isn’t worthwhile - I don’t need perfection or even the best. Enjoy your bottle dynamo; I enjoy mine and feel confident that it would both reliably ‘guide’ me through a long journey in the dark and wouldn’t be significantly sapping … that’ll do for me. The AXA that you have is considered a step up from the Union and Soubitez dynamos that I use.

Reasonable LED lights (at least adequate for country lanes and cycle tracks) don’t need to be expensive and, relatively speaking, mine are inexpensive. I reckon that, if need be, I could repurchase the front and back ones that I used tonight and likely have change from £35. Such relatively inexpensive LED lights are, IME, multiple times better than the halogen lights used say a generation ago by cyclists who covered many miles in the dark.

[rjb]

If you are on a tight budget then a dynamo will power a MR16 12v led bulb, Watts don't seem to be a problem.
You won't have a standlight with this arrangement.

[Bob999]

Nice idea about the MR16! But I had decided that I definitely wanted standlights back and front rather than live in fear at each junction. Ordered some lights now, I took up Carlton's '£35 budget limit challenge' but went 8 pence over!

[Bob999]

Evening, would just like to post a 'one year on' report. Still using the same bottle dynamo, 'cheapie' LED lights and wiring for commuting every day, plus rides. About 5 miles of my commute is unlit, the rest lit.

It has all been perfectly fine, have the cheapest Marathon tyres so they have the track for the bottle. Hasn't slipped once, it's rained plenty. There's been no problem with the connections and the light thrown is excellent on unlit roads, all down to German standards I understand. I can't think that I'd need any more light in this sort of riding environment. I no longer dream of "upgrading" to a dyno-hub. There is the constant song of inefficiency of course! - not something that troubles me, and also when it's off it's off.

So thanks for all the tips and advice, one happy punter here.

[SimonCelsa]

Good to hear a happy punter.

I use a similar set up on my tandem, the only niggle I have is that during daylight hours the bottle dynamo tends to 'spring' into action when I go over bumps, necessitating reaching down to pull it back off the tyre and into the stowed position. One day I'm going to grab a handful of moving spokes by mistake!!

It also seems impossible to open it up (without wrecking something). I'd like to take a look inside and maybe give it some maintenance every now and then but cannot see an easy way of doing this.

But yes, on the whole, cheap, reliable and a good light source.