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Dynamo/LED power conditioning



 
 
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  #1  
Old May 3rd 18, 03:49 AM posted to rec.bicycles.tech
bob prohaska
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Posts: 48
Default 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


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  #2  
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).

  #3  
Old May 3rd 18, 04:58 AM posted to rec.bicycles.tech
Frank Krygowski[_2_]
external usenet poster
 
Posts: 7,063
Default Dynamo/LED power conditioning

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
  #4  
Old May 3rd 18, 06:10 AM posted to rec.bicycles.tech
SMS
external usenet poster
 
Posts: 8,331
Default Dynamo/LED power conditioning

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.

  #5  
Old May 3rd 18, 06:22 AM posted to rec.bicycles.tech
David Scheidt
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Posts: 1,268
Default Dynamo/LED power conditioning

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
  #6  
Old May 3rd 18, 07:46 AM posted to rec.bicycles.tech
Ralph Barone[_4_]
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Posts: 174
Default Dynamo/LED power conditioning

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




Three white LEDs in series probably needs nearly 10-12 V just to overcome
the diode drop. Try just two in series and see if that helps things.

  #7  
Old May 3rd 18, 01:25 PM posted to rec.bicycles.tech
Sepp Ruf
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Posts: 217
Default Dynamo/LED power conditioning

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.
  #8  
Old May 3rd 18, 02:00 PM posted to rec.bicycles.tech
[email protected]
external usenet poster
 
Posts: 17
Default Dynamo/LED power conditioning

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.

bob prohaska


I am an EE. I recommend that you buy B&M front and rear lights. There's more to lighting than simply the electronic circuit. Optics play a crucial role.

You already went the expensive route by going with a hub dynamo, when you could have used a bottle generator. The key is in the light source and projection not the electrical power source. You will recover the extra cost, when you avoid your first pothole.

The only caveat is that the B&M connectors are not readily available. The B&M route the rear light through the front, even though they are in parallel.. The rear light's over-voltage protection isn't sufficiently robust. Should the front light connection fail, the rear will blow. Also, the rear feed should go through the front on/off switch for a hub generator.
  #10  
Old May 3rd 18, 04:30 PM posted to rec.bicycles.tech
Frank Miles
external usenet poster
 
Posts: 38
Default Dynamo/LED power conditioning

On Thu, 03 May 2018 06:46:07 +0000, Ralph Barone wrote:

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




Three white LEDs in series probably needs nearly 10-12 V just to
overcome the diode drop. Try just two in series and see if that helps
things.


The schematic has only two LEDs in series for each polarity of the
generator output. Assuming the LEDs are rated for more than the
generator's maximum output, there should be lots of light at 6V
(2 LEDs @ 3V each).
 




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