Hub dynamo with capacitor in light

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simonineaston
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Re: Hub dynamo with capacitor in light

Post by simonineaston »

Is that how it works? I thought it used an accelerometer...
Yes - me too. I'll see if I can find the original description.
(rides: Brompton nano & ever-changing Moultons)
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simonineaston
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Re: Hub dynamo with capacitor in light

Post by simonineaston »

See here link to page on B&M's website...
(rides: Brompton nano & ever-changing Moultons)
robc02
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Re: Hub dynamo with capacitor in light

Post by robc02 »

Very clever! I wonder what rate of deceleration is needed to trigger it. Would it, for instance be triggered when being slowed down at the foot of a steep hill? I suppose that might not be a bad thing though.

I don't suppose most other road users would recognise it as a brake light but it might serve to draw a bit of extra attention which could be beneficial.
Jdsk
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Re: Hub dynamo with capacitor in light

Post by Jdsk »

Stroud Active wrote: 10 Jun 2021, 10:58pm I've taken the back light apart. Inside are 4 diodes and an LED. i.e: a rectifier. There's no capacitor so it has no ability to hold charge. I believe the old front light was running as the master and feeding AC when the wheel was spinning and DC from capacitor when stopped. I'll read the specs of the old and new front light.

The old front light was a Spanninga Kendo+ with an XDA label on it https://spanninga.com/product/kendo/
The rear light looks like one of these which is also a Spanninga unit, a Pixeo: https://spanninga.com/product/pixeo/

The description doesn't eliminate all doubt but it does suggest that the safe-stop function is relying on the front light.
"The dynamo version of the PIXEO features the innovative Safe-Stop function. This function makes the light burn for 4 extra minutes after the bike stops and increases the safety for you as a cyclist tremendously."

"* The dynamo version of the PIXEO is connected to the dynamo (3W) via the headlamp."

The new front light is one of these https://www.bikester.co.uk/busch-muelle ... 23459.html

I've seen this Pixeo XS on Amazon and I think you can see a capacitor through the lens: https://www.amazon.co.uk/dp/B007MJTKIA? ... yp_imgToDp
Yes, I suspect the new B+M front light doesn't internally provide a rear standlight function.

Have you got B+M's own guide? And they're good at answering email.

Jonathan

PS: Yes, everyone assumes that my brake light works off an accelerometer. : - )
wjhall
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Joined: 1 Sep 2014, 8:46am

Re: Hub dynamo with capacitor in light

Post by wjhall »

i have two bicycles fitted with Axa Ray Steady rear lamps connected in parallel to front lamps directly across bottle dynamos. The front lamps are different generations of B&M units. One dynamo is an Axa-HR with clipper diodes, the other is a Miller, without clippers.

The rear standlight function works perfectly, which is what I would expect from a lamp with STANDLICHT printed across the plastic.

From my recollection when fitting them the two terminals on the front lamp are connected directly to each other, the resistance between them measuring zero ohms on a multimeter. They are there for mechanical convenience in attaching the rear wiring, not to provide an electrical function. As it happens both my bottle dynamos are at the rear and the parallel connections go separately from them to front and rear lamps.

As pointed out in some earlier posts in this thread the answer to what the connections do and what you can connect to them should be in the manufacturer's documention, preferably as a simple circuit diagram. If it is not, then the manufacturer deserves to be asked for the information.
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freiston
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Re: Hub dynamo with capacitor in light

Post by freiston »

robc02 wrote: 11 Jun 2021, 10:15am Very clever! I wonder what rate of deceleration is needed to trigger it. Would it, for instance be triggered when being slowed down at the foot of a steep hill? I suppose that might not be a bad thing though.

I don't suppose most other road users would recognise it as a brake light but it might serve to draw a bit of extra attention which could be beneficial.
I have such a rear light (this one) but I cannot report on its effectiveness because, try as I might, I find it impossible to watch the light whilst braking.
Disclaimer: Treat what I say with caution and if possible, wait for someone with more knowledge and experience to contribute. ;)
2_i
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Joined: 25 Feb 2020, 3:12am

Re: Hub dynamo with capacitor in light

Post by 2_i »

Historically, there has been only one bike dynamo (Jenymo) in the market with a built-in backup, but it was a bottle, not a hub dynamo. The backup relied on rechargeable cells, rather than a capacitor - there were no supercaps yet at the time. Rear lights with backups are not that expensive. For safety it is worth recovering the functionality.
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Sum
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Joined: 17 Jul 2010, 9:13am

Re: Hub dynamo with capacitor in light

Post by Sum »

Stroud Active wrote: 10 Jun 2021, 10:58pm I've taken the back light apart. Inside are 4 diodes and an LED. i.e: a rectifier. There's no capacitor so it has no ability to hold charge. I believe the old front light was running as the master and feeding AC when the wheel was spinning and DC from capacitor when stopped. I'll read the specs of the old and new front light...(snip)
I would be interested to see the internals of the rear light you've taken apart. Can you post up some pictures please?
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