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Old May 3rd 18, 04:36 AM posted to rec.bicycles.tech
Frank Miles
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Posts: 38
Default Dynamo/LED power conditioning

On Thu, 03 May 2018 02:49:21 +0000, bob prohaska wrote:

I finally caved and bought a Shimano dh-3n72 hub for use on my exercise
bike. It works fine, but the LEDs flicker quite noticeably at all
speeds. The circuit puts series trios of LEDs in inverse parallel across
the dynamo, so each trio lights on alternate half- cycles. The flicker
wasn't visible with the old Soubitez roller, because it was working at
about 6x higher frequency. The circuit is at
http://www.zefox.net/~bob/bicycle/schematic.gif The point of the design
is to eliminate rectifier losses, which are substantial at low voltage.

The new setup might be ok for fast riding. At low speeds and in traffic
I'm less sure I'll like it and fairly certain bystanders won't like it
at all, especially at night. As a DRL it certainly aids conspicuity 8-)

Can anybody point me to a discussion of what outfits like B&M use in
their dynamo-powerd LED headlights? I've searched intermittenly but
never hit the right keywords.

Thanks for reading, and any guidance.

bob prohaska


Any chance the generator was intended for a smaller wheel size?
I've got a Shimano generator (single LED with a schottky bridge rectifier)
and I don't notice flicker unless I'm going very slowly (5mph).

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