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
  #11  
Old May 3rd 18, 05:24 PM posted to rec.bicycles.tech
Jeff Liebermann
external usenet poster
 
Posts: 2,826
Default Dynamo/LED power conditioning

On Thu, 3 May 2018 02:49:21 -0000 (UTC), 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.


https://bike.shimano.com/en-EU/product/component/deorelx-t670/DH-3N72.html
The spec sheet doesn't say how many poles in the hub. My guess(tm) is
the same as the DH-3D71 with 28 poles. So, all I now need is the
wheel size (actually, the hub center to ground distance would be
better), and the minimum speed at which your exercise machine would be
expected not to flicker.

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.


If that's true, then there may be something wrong with the Shimano
dynamo. Got any electronics test equipment, such as an oscilloscope?
Take a look at the dynamo output with no load and with the light
attached. Measure the frequency at various speeds. There may also be
something wrong with the light, such as having one phase (branch) of
the LED string shorted. Either way, I would expect to see an
asymmetry in the AC waveform which would accentuate any flicker. If
one phase in the light were shorted, then it might be triggering some
kind of protection circuit inside the Shimano hub.

What bothers me is that you say:
"flicker quite noticeably at all speeds".
That's difficult to do when the Shimano hub probably produces a
frequency of 30Hz or greater at operating speeds, which should not be
visible as a flicker. Other than an overcurrent protection circuit
failure in the Shimano hub, I can't imagine how that would be
possible.

Incidentally, if you don't have an oscilloscope, try using a PC and a
sound card:
https://windowsreport.com/oscilloscope-software-pc-laptop/

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

--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Ads
  #12  
Old May 3rd 18, 06:44 PM posted to rec.bicycles.tech
SMS
external usenet poster
 
Posts: 8,281
Default Dynamo/LED power conditioning

On 5/3/2018 6:00 AM, wrote:
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.


There are several good options for dynamo lights. A little more
expensive than B&M is this one: https://www.amazon.com/dp/B072K6PN64
with better optics. Cheaper he
https://www.bike24.com/1.php?content=8;product=214107




  #13  
Old May 3rd 18, 10:43 PM posted to rec.bicycles.tech
[email protected]
external usenet poster
 
Posts: 1,322
Default Dynamo/LED power conditioning

On Wednesday, May 2, 2018 at 9:49:23 PM UTC-5, 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 have this dynamo hub.
http://www.starbike.com/p/Shimano-dy...er-36H-5206-en

And two(2) of these lights hooked to the dynamo.
http://www.starbike.com/en/busch-and...umotec-iq-cyo/

I can ride at any speed, 4-5 mph or greater, and have good lighting without any flickering. So I'd say something is wrong with either the hub or lights you are using.
  #14  
Old May 4th 18, 03:16 AM posted to rec.bicycles.tech
Andre Jute[_2_]
external usenet poster
 
Posts: 8,651
Default Dynamo/LED power conditioning

On Thursday, May 3, 2018 at 3:49:23 AM UTC+1, 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


Bob, it looks like you're trying to make more light than the dynamo can provide current for: that's just too many diode drops, so try fewer LEDs. I have had my doubts about Busch und Muller lamps in the past, and also the bullying marketing tactics of their fans, but their current Cyo lamp is perfectly adequate, and leaves enough power for the rear lamp. It's probably cheaper than anything as good that you can build, and it has roadable optics with a car-friendly cutoff, a standlight and auto-switching. Sorting that lot out from their circuit, which is full of unknown and unmarked components, will theoretically leave you with the information you want. But how to eliminate what you don't want is the problem.

My experience is that Shimano dynamos, of which the -72 was once the most desirable model, come up to maximum output faster than SON dynamos, that is, provide a steady, useful light at lower speed. So if you see flickering at low speed with a Shimano hub dynamo, you're overloading it.

AJ
  #15  
Old May 4th 18, 03:36 AM posted to rec.bicycles.tech
bob prohaska
external usenet poster
 
Posts: 44
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

  #16  
Old May 4th 18, 04:27 AM posted to rec.bicycles.tech
bob prohaska
external usenet poster
 
Posts: 44
Default Dynamo/LED power conditioning

Ralph Barone wrote:

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.

Yes, it might help a little. It turns out (after a short night ride) that
the flicker is most apparent only to someone looking directly at the
LEDs, which operate on alternate half-cycles. An observer seeing the
illuminated field notices much less flicker, though it never goes away
at any speed I can maintain.

Given the complexity of the circuits described in the links Sepp posted
I am very tempted to try living with what I've got. A MOSFET bridge and
peaking capacitor seem like a decent next step if the flicker causes
serious trouble.

Thanks for writing!

bob prohaska

  #17  
Old May 4th 18, 05:06 AM posted to rec.bicycles.tech
bob prohaska
external usenet poster
 
Posts: 44
Default Dynamo/LED power conditioning

wrote:

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.


Optics do play a crucial role, and they've gotten much better since I put the
existing system together around 2007. My choice of a dh-3n72 was driven
mostly by availability and a sub-$90 price on Amazon. It'd have been closer
to $80 had I not lost the whack-a-mole game that must be won to secure
free shipping.

You already went the expensive route by going with a hub dynamo,

Well, at least I didn't get a Schmidt 8-)

when you could have used a bottle generator.


I'm unaware of any well-made, modern sidewall generators for bicycles.
For many years I used an old Soubitez roller dynamo, replacing it only
after plastic mounting parts started cracking. In performance terms I
think it's better than a hub dynamo (less weight, better output, acceptable
drag) but they are no longer in production and scarce on Ebay. The one
bottle dynamo I tried got hot to the touch at 10 mph.

I will admit that the quietness of the dh-3n72 is very nice. It also
contributes mightily to the illusion of minimal drag......

The setup I'm posting about is now used mostly for exercise and isn't
ridden much at night. The extreme flicker came as a surprise when first
seen and greatly annoyed me. As I think it over, and look at the options,
it may be best just to live with it. The goal there is daytime conspicuity,
and that is satisfied in spades.

If I get a B&M headlight, it'll probably go on my UpTown 8 grocery chaser.
It's hard to find bulbs for the halogen front light, and that bike is at
least occasionally ridden in earnest at night.

Thanks for writing,

bob prohaska

  #18  
Old May 4th 18, 05:05 PM posted to rec.bicycles.tech
Frank Krygowski[_4_]
external usenet poster
 
Posts: 6,042
Default Dynamo/LED power conditioning

On 5/4/2018 12:06 AM, bob prohaska wrote:

I'm unaware of any well-made, modern sidewall generators for bicycles.
For many years I used an old Soubitez roller dynamo, replacing it only
after plastic mounting parts started cracking. In performance terms I
think it's better than a hub dynamo (less weight, better output, acceptable
drag) but they are no longer in production and scarce on Ebay. The one
bottle dynamo I tried got hot to the touch at 10 mph.


I'm curious, what make of dynamo got hot at 10 mph?

I have ancient Union bottles on two bikes. I don't recall them ever
getting beyond very slightly warm - I'd guess maybe 90 degrees Fahrenheit.

This place has bottle dynamos:
https://www.sjscycles.co.uk/dynamos-bottle/
I've bought other stuff from them. Price and shipping speed seem very
competitive with American sources, and selection tends to be much better.

If I get a B&M headlight, it'll probably go on my UpTown 8 grocery chaser.
It's hard to find bulbs for the halogen front light, and that bike is at
least occasionally ridden in earnest at night.


This place has been a good source for bulbs of all kinds:
http://www.reflectalite.com/
They also have LEDs that are drop-in replacements for halogen dyno
bulbs. I bought one for a friend and have another in a headlamp that
I've only bench tested in my basement. It seems very good, but I haven't
tried it on the road. It's not yet needed on any of my bikes.

--
- Frank Krygowski
  #19  
Old May 4th 18, 06:09 PM posted to rec.bicycles.tech
bob prohaska
external usenet poster
 
Posts: 44
Default Dynamo/LED power conditioning

Jeff Liebermann wrote:

If that's true, then there may be something wrong with the Shimano
dynamo. Got any electronics test equipment, such as an oscilloscope?
Take a look at the dynamo output with no load and with the light
attached. Measure the frequency at various speeds. There may also be
something wrong with the light, such as having one phase (branch) of
the LED string shorted. Either way, I would expect to see an
asymmetry in the AC waveform which would accentuate any flicker. If
one phase in the light were shorted, then it might be triggering some
kind of protection circuit inside the Shimano hub.

Alas, no test equipment beyond a cheap DVM with 400mA AC current range.

I get 28 "notches" per turn on the hub, in a 27" wheel. Current reaches
400 mA at a modest speed, probably 10 mph. Voltage (which I can't measure
simultaneously) reaches 10.3 V at a similar speed and won't exceed 10.5 V
with any effort I can realistically exert.

There is of course no guarantee the meter is true RMS and the wafeforms
are not sinusoidal, but the numbers suggest nothing radically wrong with
either the hub or the LEDs (all six look about the same).


What bothers me is that you say:
"flicker quite noticeably at all speeds".
That's difficult to do when the Shimano hub probably produces a
frequency of 30Hz or greater at operating speeds, which should not be
visible as a flicker. Other than an overcurrent protection circuit
failure in the Shimano hub, I can't imagine how that would be
possible.

Incidentally, if you don't have an oscilloscope, try using a PC and a
sound card:
https://windowsreport.com/oscilloscope-software-pc-laptop/


There's an audio signal processing app for iPads that can do something
crudely similar. It's not an oscilloscope, per se, but does give a
waveform display. If the puzzle gets deeper it might be worth trying.
At the moment I see no reason to suspect malfunction, either in the
dynamo or the LEDs.

Part of the issue can be seen in a darkened garage: Spinning the front
wheel casts double shadows from the two sets of LEDs. Without the shadow
effect the scene looks much less strange. With a shadow, or looking
directly at the LEDs, it's quite conspicuous. I suspect the lateral
"movement" is what catches the eye.

The roller dynamo has 8 poles and runs at roughly 20 times wheel speed.
Even with 28 poles the frequency of the hub dynamo is roughly 6x lower
than the roller setup, which seems enough to account for the flicker,
especially when combined with the alternating groups of LEDs.

It looks like the only defect is my failure to consider the lower
operating frequency of the hub dynamo. Now the question is what, if
anything, to do about it.

Thanks to everybody who replied, this has been a most informative
discussion!

bob prohaska

  #20  
Old May 4th 18, 06:19 PM posted to rec.bicycles.tech
bob prohaska
external usenet poster
 
Posts: 44
Default Dynamo/LED power conditioning

Andre Jute wrote:

My experience is that Shimano dynamos, of which the -72 was once the most desirable model, come up to maximum output faster than SON dynamos, that is, provide a steady, useful light at lower speed. So if you see flickering at low speed with a Shimano hub dynamo, you're overloading it.


I believe you've hit the nail on the thumb 8-)

A DPST switch wired to shunt one LED in each branch is probably the
simplest fix. That'll give better light at low speed. The flicker
is useful during the day and tolerable over about 10 mph at night.

Thank you for writing!

bob prohaska

 




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 04:50 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 07:23 AM.


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.