Dynamo/LED power conditioning

On 2018-05-07 12:25, Ian Field wrote:


"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.


Nah. $0.03 a pop for the 100V version in reel quatities:

http://www.smc-diodes.com/propdf/DSS...73%20REV.A.pdf

However, in a dynamo circuit I'd try to use active rectification.


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.


That's what bi-directional TVS'es are for, cheap insurance :-)

--
Regards, Joerg

http://www.analogconsultants.com/

On 2018-05-08 11:50, sms wrote:
On 5/6/2018 10:01 AM, Joerg wrote:

snip

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?

I have dynamo wheels on several bicycles and it's nice to just go. Not
worry about charging lights off the bike.


I don't worry either. When I return home the bike gets plugged in just
like electric cars do. Except it's only a lighting battery which charges
fast. Turns off automatically but I usually unplug it before going to
bed. That way both bikes are always charged. Not 100% topped off but 90%
because that greatly prolongs Li-Ion life and suffices even for really
long rides.


OTOH the dynamo lights are not suitable for all situations. The
multi-use paths around here are generally alongside creeks and are
unlit, with a lot of twists and turns as they go over and under roads,
waterways, and railroad tracks. You need a higher-power light,
especially if you want to proceed at an expeditious pace.


That is a key reson why dynamo-only will never work for me. I ride on
dirt a lot of times, singletrack. There are tricky sections with loose
rocks strewn around, diagonal ruts and other fun stuff. Miss one of
those because the light was too dim and a nasty spill could happen. So
there has to be at least a buffer battery. A sizeable one because some
routes can take 2h at rather modest speeds.


It would be possible to have a hub dynamo capable of powering higher
power lights but there seems to be little demand for it now that there
are so many Li-Ion powered high-power lights available for relatively
low prices.


Yeah, it's not a priority for me. On cross-country trips that would be
another matter although I have seen longhaul mountain bikers who had
strapped a solar panel to the front baggage roll. Recharging while
rolling would be nice but the advantages are so slim that it isn't worth
much expense or effort for me.

--
Regards, Joerg

http://www.analogconsultants.com/

Jeff Liebermann wrote:

:Assuming you own an automobile, what do you check before you go for a
:ride or drive? Got enough gasoline? Fluid levels within limits? Tire

I check nothing. I get in the car and drive. If the tires on the
drivers side were flat, I would notice. behond that, I dont' check
things before I trip. if the gas gauge says low, I put gasoline in
it. I check the oil at the same time. I check the tire pressure from
time to time. I observe the tail lights nd brake lihgts when I drive
at night. I look at the pads when I put the snow tires on and take
them off (and the shop does similar checks when they change the oil.).

I expect my car to Just Work.

I expect my bike to do the same. I check the tire pressure rather
more often, but the pre ride checklist consists of dropping the bike
frm fpour inches or so, and listening to it. Unexpected noises are
investigated. They're normally "itre needs air". secon most common
problem is "loose fender quick disconnect". The bike needs uch more
work per mile than a car does, but they're still generally ready to
ride.

--
sig 112

On Tuesday, May 8, 2018 at 3:43:00 PM UTC-4, Joerg wrote:
On 2018-05-08 12:01, Frank Krygowski wrote:
On Tuesday, May 8, 2018 at 2:10:43 PM UTC-4, Joerg wrote:
Once I waited at a
red light and a Harley rider pulled up next to me. His big headlight was
about the same brightness as mine except more spectrally pleasant, not
as "hospital-grade" white as mine.

I remain absolutely astonished that people think the headlight on a bicycle has
to have the same brightness as the headlight on a motorcycle capable of 100+ mph.


You as an engineer should know this:

https://policedriver.com/over-driving-your-headlights/

So your 100mph statement is quite ridiculous.

So is your logic. Is it a 100+ mph motorcycle? Yes, whether you like it or not,
and whether you would ride it at that speed or not.

Are its headlights adequate only at 60 mph? That has not been proven, because
the motorcycle may have super headlights. It doesn't matter. What should be
clear is that a bicycle does not need a headlight as bright as a motorcycle's.
No matter how fast you pretend to be on your bike (if that's your shtick today -
it flip-flops regularly) you don't need even a 45 mph light.

Also, as I've said many times before I like to be seen. Since I have
these bright lights I have noticed a substantial drop in cases where car
drivers pull out in front of me. Objective accomplished, and at a very
modest cost.

You need to look up confirmation bias. And until you do, you need to buy a
dozen pairs of the lucky socks I'm willing to sell you. I _know_ those are
what has kept me from having any car-bike wrecks in my 40+ years of riding.
I just know it!

Seriously, I just never have cars pull out in front of me. Your magic is way,
way weaker than mine. But is it magic? Or is it technique?

- Frank Krygowski

On Tuesday, May 8, 2018 at 5:28:05 PM UTC-4, Joerg wrote:

1. Hardly any bike or wheel set in America has a hub dynamo. So you have
to buy new spokes and spoke it in.

Horrors!!

Or more seriously: Too bad you a) can't find a wheel for sale using this
internet thing; and b) aren't competent at wheel building.

2. When you get to an intersection, traffic light or whetever where you
need to stop many of these lights eitehr go out or they enter a "stand
light" mode which is rather dim.

Seriously, you're terrified of someone hitting you from the _front_ when you're
at a traffic light? Geez...

3. They still can't hold a candle to MagicShine and clones of it. 8W
into a Cree XM-L is a different caliber than 3W.

And a MagicShine can't hold a candle to an aircraft landing light. But bicycling
equipment isn't about excess, it's about efficiency. It's why real cyclists
don't use motorcycle gage spokes, inch wide chains, tubes with 1/8" walls, etc.

4. The StVZO lights for dynamos that I have seen have a much too sharp
cut-off line which is uncomfortable on an uneven road or on the MTB.

Gosh, how do you ever drive a car at night with that same sort of cut-off?

5. The prices of many of those lights are outrageous. Often fat
three-digits.

Yet this lowly retired professor has afforded about five of them. Sad that your
economic situation is so dire.

I don't want a $200 headlight on my bike only to have it
ripped off by a hobo a few months later.

In over 40 years of avid adult cycling, I've had two cyclometers nicked,
obviously by kids who had no use for them, because Avocet mounts and senders
are damned uncommon. Nothing else has ever been stolen. If you're that paranoid
about the hobos in Cameron Park, use thread lock compound on security fasteners.
Or move.

- Frank Krygowski

Jeff Liebermann wrote:
On Mon, 7 May 2018 13:21:02 +0000 (UTC), David Scheidt
wrote:

Theodore Heise wrote:

:Someone noted elsethread the great variation in user requirements,
:and the choice between dynamos and rechargeables is certainly
:affected by them. I need a light only infrequently, so for me a
:dynamo would largely be wasted weight and clutter on the bike. On

Ah, but it would just work. Get on the bike, and ride. a rechargable
light would have to be found, put on the bike, and discover the
batteries are dead.

Assuming you own an automobile, what do you check before you go for a
ride or drive? Got enough gasoline? Fluid levels within limits? Tire
pressure look normal? Engine warning light on? For fanatics, does
the add-on OBD II display panel show anything unusual? Having driven
rolling wrecks during college, walking around the vehicle to see what
has fallen off or was stolen in the night was a regular ritual.

Same with my bicycles. Do you check the air pressure in your tires
before riding? I don't, but I give the tires a good squeeze as a
crude pressure check and pump as needed. My favorite mistakes are a
loose quick release, a loose nut from an unfinished repair, and my
folding pedals in the folded position. I take a quick look at the
frame and gears for any sign of damage. I check for my seat bag of
tricks, which contains tools, parts, munchies, and a few dollars.

Batteries do not provide a visual or mechanical indication of SoC
(state of charge), but you can add something like this:
https://www.ebay.com/itm/Lithium-ion-Charging-Battery-Voltage-Capacity-Percent-Level-LED-Indicator-18650/181692946263
Some headlights have a similar indicator built in. I use a DVM
(digital voltmeter) instead.

More problematic is the tail light, which usually runs on alkaline AA
or AAA cells. I haven't seen one with a SoC indicator and would not
expect to see one as the added circuitry and display would probably
cost more than the tail light. So, I run the alkalines until they
die, and carry a few spare NiMH cells which I rotate as needed. With
LSD (low self discharge) NiMH cells, they remain mostly charged for
months.

While just jumping onto the bicycle and going for a ride is a nice
thought, the reality is that we all do some manner of pre-flight check
before riding. So, why is it so painful to add a headlight battery
test to the checklist?


For the fun bikes I probably would check the pressures and so on, for
lights less, so more likely just fit the lights which are generally have
charge at least enough for a few rides.

The commute bike though has two rears which I use until one looses charge,
and then charge. Similar with the front light, but in generally lasts
longer since it has run time of a day on low, so though I do use it as a
day light, and commute hrs per week is 12hrs.

I do agree though since most people change into cycling gear, that worrying
about putting a light on isn’t much of a hassle really.

Roger Merriman

Frank Krygowski wrote:
On Tuesday, May 8, 2018 at 2:10:43 PM UTC-4, Joerg wrote:
Once I waited at a
red light and a Harley rider pulled up next to me. His big headlight was
about the same brightness as mine except more spectrally pleasant, not
as "hospital-grade" white as mine.

I remain absolutely astonished that people think the headlight on a bicycle has
to have the same brightness as the headlight on a motorcycle capable of 100+ mph.

- Frank Krygowski


How bright a light looks, at a glance isn’t generally very accurate, my
torch looks as bright as the light I use for MTBing in that both look
bright, in terms of ooh that’s a bright light.

Motorbike lights generally don’t tend to be terribly powerful, for a
combination of reasons. One of the main reasons, is mostly motorbikes
aren’t used after dark.

My commute bike I have one of the Exposure Strada 600 it has a shaped beam
not German standard but certainly intended not to blind, and a remote
switch, so I generally run it on low and only kick up if needed, which is
remarkably few places, on my commute.

As ever mileage varies the 1000 lumen MTB light in certain places can feel
under powered, though that’s far from norm, even off road I don’t generally
use it at full chat, though does depend on where, wide tracks etc are a
easy low setting, it’s only low speed twisty stuff that needs the full
power, which is also where the only MTB dynamo light fell down, ie it could
push out the power at higher speeds where generally you don’t need that
much power, but reduces on the slower technical stuff, where you really do!

Roger Merriman

On 2018-05-08 20:23, Frank Krygowski wrote:
On Tuesday, May 8, 2018 at 5:28:05 PM UTC-4, Joerg wrote:

1. Hardly any bike or wheel set in America has a hub dynamo. So you have
to buy new spokes and spoke it in.

Horrors!!

Or more seriously: Too bad you a) can't find a wheel for sale using this
internet thing; and b) aren't competent at wheel building.


Your usual premature conclusions. I am very particular about what
quality wheel I want. I know how to build a wheel but I don't want to do
it. Simple, really.


2. When you get to an intersection, traffic light or whetever where you
need to stop many of these lights eitehr go out or they enter a "stand
light" mode which is rather dim.

Seriously, you're terrified of someone hitting you from the _front_ when you're
at a traffic light? Geez...


I know you don't understand these things but there are drivers who come
tearing around on a left turn cutting across the "empty" left turn lane
of the road on the left. To the point where the yellow lines have worn.

There are reasons for vehicle lights. A bicycle is a vehicle.


3. They still can't hold a candle to MagicShine and clones of it. 8W
into a Cree XM-L is a different caliber than 3W.

And a MagicShine can't hold a candle to an aircraft landing light. But bicycling
equipment isn't about excess, it's about efficiency. It's why real cyclists
don't use motorcycle gage spokes, inch wide chains, tubes with 1/8" walls, etc.


A lot of cyclists simply do not understand it and you seem to be one.
Those that I convinced of the advantages of thick tubes were elated
about the sudden absence of flats.


4. The StVZO lights for dynamos that I have seen have a much too sharp
cut-off line which is uncomfortable on an uneven road or on the MTB.

Gosh, how do you ever drive a car at night with that same sort of cut-off?


Mine does not have such sharp cut-off as I sah in StVZO bike lights and
its suspension is a lot harder than on the bike. Also, look at your
steering column items and you might discover something very practical:
High beam. Something bike manufacturers don't seem to understand. Get it
now?


5. The prices of many of those lights are outrageous. Often fat
three-digits.

Yet this lowly retired professor has afforded about five of them. Sad that your
economic situation is so dire.


I tend not to waste money. Comments like yours made me understand why so
many people can't get out of debt even by the time they retire. They
can't manage money.


I don't want a $200 headlight on my bike only to have it
ripped off by a hobo a few months later.

In over 40 years of avid adult cycling, I've had two cyclometers nicked,
obviously by kids who had no use for them, because Avocet mounts and senders
are damned uncommon. Nothing else has ever been stolen. If you're that paranoid
about the hobos in Cameron Park, use thread lock compound on security fasteners.
Or move.


I've had whole bikes stolen, gone, never recovered.

--
Regards, Joerg

http://www.analogconsultants.com/

On 2018-05-08 20:13, Frank Krygowski wrote:
On Tuesday, May 8, 2018 at 3:43:00 PM UTC-4, Joerg wrote:
On 2018-05-08 12:01, Frank Krygowski wrote:
On Tuesday, May 8, 2018 at 2:10:43 PM UTC-4, Joerg wrote:
Once I waited at a
red light and a Harley rider pulled up next to me. His big headlight was
about the same brightness as mine except more spectrally pleasant, not
as "hospital-grade" white as mine.

I remain absolutely astonished that people think the headlight on a bicycle has
to have the same brightness as the headlight on a motorcycle capable of 100+ mph.


You as an engineer should know this:

https://policedriver.com/over-driving-your-headlights/

So your 100mph statement is quite ridiculous.

So is your logic. Is it a 100+ mph motorcycle?


Doesn't matter whether a car or a motorcycle. Going 100mph with regular
headlights is reckless.


... Yes, whether you like it or not,
and whether you would ride it at that speed or not.


Huh?


Are its headlights adequate only at 60 mph? That has not been proven, because
the motorcycle may have super headlights.


They generally don't. Sit on one and look.


It doesn't matter.


This statement makes any further discussion fruitless.

[...]

--
Regards, Joerg

http://www.analogconsultants.com/

Joerg wrote:

On Tuesday, May 8, 2018 at 2:10:43 PM UTC-4, Joerg wrote:
Once I waited at a
red light and a Harley rider pulled up next to me. His big headlight was
about the same brightness as

This statement makes any further discussion fruitless.

IFTFY.
EOD.