A Cycling & bikes forum. CycleBanter.com

Go Back   Home » CycleBanter.com forum » rec.bicycles » Techniques
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

Dynamo/LED power conditioning



 
 
Thread Tools Display Modes
  #1  
Old May 3rd 18, 03:49 AM posted to rec.bicycles.tech
bob prohaska
external usenet poster
 
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


  #2  
Old May 3rd 18, 04:36 AM posted to rec.bicycles.tech
Frank Miles
external usenet poster
 
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: 8,338
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
external usenet poster
 
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, 01:25 PM posted to rec.bicycles.tech
Sepp Ruf
external usenet poster
 
Posts: 218
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.
  #7  
Old May 4th 18, 03:36 AM posted to rec.bicycles.tech
bob prohaska
external usenet poster
 
Posts: 48
Default Dynamo/LED power conditioning

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

  #8  
Old May 6th 18, 06:01 PM posted to rec.bicycles.tech
Joerg[_2_]
external usenet poster
 
Posts: 5,552
Default Dynamo/LED power conditioning

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/
  #9  
Old May 7th 18, 08:25 PM posted to rec.bicycles.tech
Ian Field
external usenet poster
 
Posts: 250
Default Dynamo/LED power conditioning



"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.

  #10  
Old May 8th 18, 01:13 PM posted to rec.bicycles.tech
Tosspot[_3_]
external usenet poster
 
Posts: 1,202
Default Dynamo/LED power conditioning

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 :-(

 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
conditioning question teachndad Unicycling 6 September 9th 08 08:18 PM
New Brooks B17 Conditioning Question [email protected] Techniques 46 October 9th 06 05:10 PM
Dynamo on a Uni for GPS/PPC power mikepenton Unicycling 15 February 3rd 05 05:50 PM
Conditioning/Getting in shape Bent Pedals Recumbent Biking 23 October 19th 03 09:48 PM
Stretching & Physical Conditioning links Luther Blissett Australia 2 August 27th 03 02:25 PM


All times are GMT +1. The time now is 06:42 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.
Copyright 2004-2018 CycleBanter.com.
The comments are property of their posters.