Dynamo/LED power conditioning

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

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).

On Wednesday, May 2, 2018 at 10:49:23 PM UTC-4, 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.

I'm a mechanical engineer, not an electrical engineerm and I can't say about
B&M, but I had one off-brand LED headlight that died by burning up its LED, so I
took it apart and replaced the LED (with great trouble). Turns out the
electronics were simple: IIRC just a bridge circuit, a voltage regulator
and a few miscellaneous components. And again, it failed by cooking the LED.

But I've also opened a low-end B&M headlamp. I can tell you that it had a heck
of a lot more complication in its electronics. Lots of surface mount stuff that
I can't identify. So I do wonder what it all is.

But again, I'm an ME, not an EE.

BTW, I fitted an ancient Sturmey-Archer Dynohub with a high power LED. My
circuit had the headlight and taillight anti-parallel, with no rectification.
So half a cycle goes to the headlight, half to the taillight. It flickers,
but it's not a bother. 20 poles, but above 10 mph I don't notice the flicker
much.

- Frank Krygowski

On 5/2/2018 7:49 PM, 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

I suspect that they use a Schottky Bridge Rectifier, with a capacitor
across the DC output, plus a couple of farads for any standlight that
switches in when stopped.

sms wrote:
:On 5/2/2018 7:49 PM, 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

:I suspect that they use a Schottky Bridge Rectifier, with a capacitor
:across the DC output, plus a couple of farads for any standlight that
:switches in when stopped.

I would not be at all surprised if the better stuff (where better
needn't mean 'more expensive' just 'better design' or maybe just
'newer design') is using a MOSFET brige. One for a bike light
wouldn't be terribly expensive, and they're substantially more
efficent than a schottky is.


--
sig 24

David Scheidt wrote:
sms wrote:
:On 5/2/2018 7:49 PM, 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.

The classic B&M circuits used rectification and current-doubling to fully
power one 1 amp led. Your 2x3S LED approach is quite different.

http://candlepowerforums.com/vb/showthread.php?430445
Good luck!

Simpler:
http://www.pilom.com/BicycleElectronics/DynamoCircuits.htm

:I suspect that they use a Schottky Bridge Rectifier, with a capacitor
:across the DC output, plus a couple of farads for any standlight that
:switches in when stopped.

I would not be at all surprised if the better stuff (where better
needn't mean 'more expensive' just 'better design' or maybe just
'newer design') is using a MOSFET bridge. One for a bike light
wouldn't be terribly expensive, and they're substantially more
efficent than a schottky is.

Not necessary though, especially at road bike velocity and (switchable to) a
(rectified) 2S max configuration for those rare low speed moments.
https://www.mtb-news.de/forum/t/nabendynamo-mosfet-mc-e-flackert-wie-wild.676394/

Joerg will surely volunteer to build an uber-efficient, but also beverage-
and wildlife-proof circuit for Bob.

Sepp Ruf wrote:
David Scheidt wrote:
sms wrote:
:On 5/2/2018 7:49 PM, 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.

The classic B&M circuits used rectification and current-doubling to fully
power one 1 amp led. Your 2x3S LED approach is quite different.

http://candlepowerforums.com/vb/showthread.php?430445
Good luck!

Simpler:
http://www.pilom.com/BicycleElectronics/DynamoCircuits.htm

:I suspect that they use a Schottky Bridge Rectifier, with a capacitor
:across the DC output, plus a couple of farads for any standlight that
:switches in when stopped.

I would not be at all surprised if the better stuff (where better
needn't mean 'more expensive' just 'better design' or maybe just
'newer design') is using a MOSFET bridge. One for a bike light
wouldn't be terribly expensive, and they're substantially more
efficent than a schottky is.

Not necessary though, especially at road bike velocity and (switchable to) a
(rectified) 2S max configuration for those rare low speed moments.
https://www.mtb-news.de/forum/t/nabendynamo-mosfet-mc-e-flackert-wie-wild.676394/


This is the sort of thing I was looking for, thank you!

bob prohaska

On 2018-05-03 19:36, bob prohaska wrote:
Sepp Ruf wrote:
David Scheidt wrote:
sms wrote:
:On 5/2/2018 7:49 PM, 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.

The classic B&M circuits used rectification and current-doubling to fully
power one 1 amp led. Your 2x3S LED approach is quite different.

http://candlepowerforums.com/vb/showthread.php?430445
Good luck!


Note the three big 470uF capacitor in the schematic. That's the "flicker
reduction trick" :-)

Problem is, electrolytic capacitors do not live long in harsh climate
conditions such as the black light enclosure baking in the glistening
Arizona desert sun for hours every week or riding around the Klondike in
a harsh winter.

For me the only proper way of lighting a bicycle is with a rechargeable
battery. The LEDs get clean DC and the battery can be recharged from any
source, even a pulsating one. That way the lights will not dim to "stand
light" or go out when waiting at a traffic light. Why should bicycle
lighting be inferior to car lighting?

--
Regards, Joerg

http://www.analogconsultants.com/

"David Scheidt" wrote in message
news
sms wrote:
:On 5/2/2018 7:49 PM, 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

:I suspect that they use a Schottky Bridge Rectifier, with a capacitor
:across the DC output, plus a couple of farads for any standlight that
:switches in when stopped.

I would not be at all surprised if the better stuff (where better
needn't mean 'more expensive' just 'better design' or maybe just
'newer design') is using a MOSFET brige. One for a bike light
wouldn't be terribly expensive, and they're substantially more
efficent than a schottky is.

SB rectifiers are rarely rated more than 60V - anything higher gets
seriously expensive.

Most of that type of AC generator vaguely resemble constant current
sources - the off load voltage can get a bit naughty.

The open voltage on a bottle dynamo can give an impressive belt, not too
sure about hub types.

Clearly; an intermittent fault in the load would kill the rectifier.

On 05/07/2018 08:25 PM, Ian Field wrote:

snip

The open voltage on a bottle dynamo can give an impressive belt, not too
sure about hub types.

I can confirm that is in fact the case for hub dynamos :-(