Flickering dynamo light

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JamesE
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Flickering dynamo light

Post by JamesE »

The front light on my new Spa tourer has an annoying but not fatal problem: it dims regularly but very briefly, about every 18-20 seconds. It's a Busch & Muller Lumotec IQ-X with a sensor that automatically puts it into daytime mode; it looks like the flicker is the light briefly dropping into daytime mode and back again. Dynamo is an SP PV-8 and there's also a Toplight Line Plus rear light and a USB-Werk attached.

I asked Busch & Muller if the light is faulty and they suggested trying a different dynamo first. Anyone got any suggestions before I try rooting out a different front wheel and swapping everything around?
Toffee
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Re: Flickering dynamo light

Post by Toffee »

Have you tried it without the usb werk attached?
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andrew_s
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Re: Flickering dynamo light

Post by andrew_s »

The USB-Werk would be my guess too.
It's got a cache battery in it, and it's possible that the dimming is it getting a regular charge state check.
JamesE
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Re: Flickering dynamo light

Post by JamesE »

Belatedly: yes, unplugging the USB-Werk appears to have done it. Not a problem for me as I only use the USB-Werk in daylight but I've mentioned it to B&M as a possible fault. I wonder if I should let Spa know, too...
albal1
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Re: Flickering dynamo light

Post by albal1 »

My lumotec lite front light flickers, and when speed up to 10mph or so it goes out completely! It is wired direct to a son 28 Dynohub. The rear is a B+m toplight plus. Whilst it works fine at all speeds. The standlight does not work.
All really annoying.
Jdsk
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Re: Flickering dynamo light

Post by Jdsk »

albal1 wrote: 8 Dec 2021, 2:27pm My lumotec lite front light flickers, and when speed up to 10mph or so it goes out completely! It is wired direct to a son 28 Dynohub. The rear is a B+m toplight plus. Whilst it works fine at all speeds. The standlight does not work.
Is this a new fault on stuff that used to work properly?

Thanks

Jonathan
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mjr
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Re: Flickering dynamo light

Post by mjr »

albal1 wrote: 8 Dec 2021, 2:27pm My lumotec lite front light flickers, and when speed up to 10mph or so it goes out completely! It is wired direct to a son 28 Dynohub. The rear is a B+m toplight plus. Whilst it works fine at all speeds. The standlight does not work.
All really annoying.
Do you mean a Lumotec Lyt? Which model? The N ones are designed for hub dynamos. I'm not sure what happens if you connect a T model to a hub.

Do you really have a Toplight Plus? I think that's now out of production (current models are Toplight Line, Toplight View, Toplight Flat and Toplight Mini, in various models) but maybe someone is still selling them. Anyway, I'd fix the faulty front light first because it's possible not enough current is reaching the rear to charge the standlight.
MJR, mostly pedalling 3-speed roadsters. KL+West Norfolk BUG incl social easy rides http://www.klwnbug.co.uk
All the above is CC-By-SA and no other implied copyright license to Cycle magazine.
albal1
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Re: Flickering dynamo light

Post by albal1 »

Thanks for the replies.

I only run the Dynohub wheel in winter. So I don't remember it doing this last winter.

Front light is : lumotec lyt led b.

Rear: B+M toplight flat plus.

A check of all wires, seems ok.
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mjr
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Re: Flickering dynamo light

Post by mjr »

albal1 wrote: 8 Dec 2021, 5:10pm I only run the Dynohub wheel in winter. So I don't remember it doing this last winter.

Front light is : lumotec lyt led b.
https://www.bumm.de/files/Produkte/Bedi ... lassic.pdf says the B is "for tyre dynamo".

I think that tyre dynamos put out DC (so strictly speaking are generators not dynamos) while hub dynamos put out AC. Some lights cope with either but not all. I'm sorry I don't have better news.

The definitive answer is probably in viewtopic.php?f=5&t=127606 or another of Brucey's posts that I did not find right now.
MJR, mostly pedalling 3-speed roadsters. KL+West Norfolk BUG incl social easy rides http://www.klwnbug.co.uk
All the above is CC-By-SA and no other implied copyright license to Cycle magazine.
Jdsk
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Re: Flickering dynamo light

Post by Jdsk »

Check the condition of all of the wires and all of the connections: disconnect, inspect, clean, reconnect.

Disconnect the rear light and see if that affects the flickering.

But I suspect that the problem is in the dynamo. Do you have access to another bike with a suitable dynamo that you can use to cross-wire to your lights as a diagnostic test?

Jonathan

PS: In my experience B+M are very good at responding to emails. But if the kit is more than a few years old it probably won't be worthwhile returning it to them for testing.
albal1
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Re: Flickering dynamo light

Post by albal1 »

Yes, on close inspection. Front light is 6-42 v DC. LED B. So it's not the correct one to use. Thanks. Any idea which one is suitable?

I,ve cleaned all contact points and checked all wires. All good. I have read similar stories on line of standlight failures. Hardly worth taking apart and checking .
May as well get a replacement. They are both a few years old now. Cheers guys
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andrew_s
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Re: Flickering dynamo light

Post by andrew_s »

6-42V DC lights are for e-bikes, running off the main battery.
Sidewall dynamos are AC, just like hubs.
Last edited by andrew_s on 8 Dec 2021, 7:59pm, edited 1 time in total.
Jdsk
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Re: Flickering dynamo light

Post by Jdsk »

albal1 wrote: 8 Dec 2021, 7:51pmAny idea which one is suitable?
Do you want to keep the existing dynamo?

Any interest in a USB charging facility?

Jonathan

PS: My latest front lamp is a B+M Cyo IQ Premium T Senso Plus:
https://www.sjscycles.co.uk/lighting/bu ... b-dynamos/
wjhall
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Re: Flickering dynamo light

Post by wjhall »

wrote:
wrote: 8 Dec 2021, 5:10pm
https://www.bumm.de/files/Produkte/Bedi ... lassic.pdf says the B is "for tyre dynamo".

I think that tyre dynamos put out DC (so strictly speaking are generators not dynamos) while hub dynamos put out AC.
In forty odd years of using 'tyre' or 'bottle' dynamos, strictly generators, I have not yet encountered one that produces DC. The distinction made by B&M probably relates to the presence or absence of a switch. Tyre dynamos can be switched off by disengaging the tyre, hub dynamos need a separate switch.

In rather more limited experience of B&M lamps, just two types about a decade apart in manufacture, both will light up with 6 V DC, and of course, with the AC from the bottle.
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mjr
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Re: Flickering dynamo light

Post by mjr »

Yes, you're correct. It seems a few DC ones were made but nothing you'll see now.

Maybe it's a faulty front light then.
MJR, mostly pedalling 3-speed roadsters. KL+West Norfolk BUG incl social easy rides http://www.klwnbug.co.uk
All the above is CC-By-SA and no other implied copyright license to Cycle magazine.
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