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Dynamo/LED power conditioning



 
 
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  #31  
Old May 7th 18, 04:00 AM posted to rec.bicycles.tech
John B.[_3_]
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Posts: 5,697
Default Dynamo/LED power conditioning

On Mon, 7 May 2018 08:15:45 +1000, James
wrote:

On 07/05/18 03:01, Joerg wrote:


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.


Bull**** alert!

We all know how reliable rechargeable batteries are, especially in harsh
environments, right?

OTOH, here is an electrolytic cap from Vishay, that has a "useful life"
of 1,000,000 hours at 40C, and 8000 hours at 125C.

https://www.vishay.com/docs/28334/118aht.pdf

(The useful life approximately halves for every 10C increase.)

If the temperature inside the electronics enclosure was much more than
80C for most of the time the light is in operation (E.g. while you're
riding and the light has forced air cooling), the engineer ought to be
shot, and that still gives a useful life of over 62500 hours.


Or perhaps 1,000,000 Km.

Or nearly 25 laps around the Earth :-)

--
Cheers,

John B.

Ads
  #32  
Old May 7th 18, 04:28 AM posted to rec.bicycles.tech
James[_8_]
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Posts: 6,153
Default Dynamo/LED power conditioning

On 07/05/18 13:00, John B. wrote:
On Mon, 7 May 2018 08:15:45 +1000, James
wrote:

On 07/05/18 03:01, Joerg wrote:


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.


Bull**** alert!

We all know how reliable rechargeable batteries are, especially in harsh
environments, right?

OTOH, here is an electrolytic cap from Vishay, that has a "useful life"
of 1,000,000 hours at 40C, and 8000 hours at 125C.

https://www.vishay.com/docs/28334/118aht.pdf

(The useful life approximately halves for every 10C increase.)

If the temperature inside the electronics enclosure was much more than
80C for most of the time the light is in operation (E.g. while you're
riding and the light has forced air cooling), the engineer ought to be
shot, and that still gives a useful life of over 62500 hours.


Or perhaps 1,000,000 Km.

Or nearly 25 laps around the Earth :-)



Oh, c'mon. Surely you're just not factoring in the baking, glistening
Arizona desert sun for hours every day... ;-)

I learned recently that the sun is 3.4% closer to the earth during the
southern hemisphere summer than during the northern hemisphere summer.

We also typically have lower pollution levels, and hence considerably
more solar radiation to contend with.

https://theconversation.com/why-does...one-hole-91850

--
JS
  #33  
Old May 7th 18, 04:46 AM posted to rec.bicycles.tech
bob prohaska
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Posts: 102
Default Dynamo/LED power conditioning

Joerg wrote:
Why should bicycle lighting be inferior to car lighting?


Does anybody make a bicycle dynamo that produces more than 3 watts
at 10 mph?

bob prohaska


  #34  
Old May 7th 18, 05:11 AM posted to rec.bicycles.tech
Frank Krygowski[_4_]
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Posts: 10,538
Default Dynamo/LED power conditioning

On 5/6/2018 11:46 PM, bob prohaska wrote:
Joerg wrote:
Why should bicycle lighting be inferior to car lighting?


Does anybody make a bicycle dynamo that produces more than 3 watts
at 10 mph?


The power produced by many (most?) dynamos depends on the load, in a
counterintuitive way. Most dynamos are approximately constant current
(about 0.5 Amp) sources, in the same way that batteries are
approximately constant voltage sources. So if you present more
resistance to the dynamo, its output voltage will rise so as to pump
that same 0.5 Amp through the higher resistance. The result is more
power. Putting two lamps in series does this.

I did this for quite a while as an experiment back in the halogen lamp
days. With my Soubitez roller dyno of the day, I needed something like
14 mph to get both lights brightly lit, so I suppose that was putting
out about six Watts. (A bottle dyno would slip doing that.)

I wouldn't bother with it today, though. What you need for night riding
is not a certain number of Watts, nor a certain number of lumens. You
need sufficient illumination of the road. The better B&M lamps certainly
give that, in spades. Those are so good there's no need to play around
with two lamps or other homebrew tricks, IMO.


--
- Frank Krygowski
  #35  
Old May 7th 18, 01:22 PM posted to rec.bicycles.tech
Theodore Heise[_2_]
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Posts: 132
Default Dynamo/LED power conditioning

On Sun, 6 May 2018 21:54:13 -0400,
Frank Krygowski wrote:
On 5/6/2018 3:19 PM, AMuzi wrote:


I think Joerg meant that the automobile current from a
12~14VAC alternator source gets run through a diode bride and
then (as switched by the regulator) through a lead-acid pile.

It's a lot of hardware for a bicycle I agree, but Joerg's
seems to work for Joerg's values of performance and
efficiency. Frank & I prefer a simple 6VAC tire drive
dynamo...


For the record, I also have a couple hub dynamos. And two of my
formerly "tire drive" dynos are now rim drive.

But yes, I certainly prefer those to fussing with recharging or
replacing or remembering batteries.


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
the other hand, if I rode in the dark often, I could easily see
the conclusion tipping the other way.

--
Ted Heise West Lafayette, IN, USA
  #36  
Old May 7th 18, 02:21 PM posted to rec.bicycles.tech
David Scheidt
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Posts: 1,346
Default Dynamo/LED power conditioning

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.

--
sig 77
  #37  
Old May 7th 18, 02:43 PM posted to rec.bicycles.tech
Theodore Heise[_2_]
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Posts: 132
Default Dynamo/LED power conditioning

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.


Sure, I get that--and don't disagree. But for me, the effort to
find the light, have a charged battery, and mount it is small. I
keep things in established places, and plan ahead. The risk of
failure is acceptable (to me).

On the other hand, I rarely need the light, and like having the
handlebar real estate available for other things. Also, my
commuter (and beater) bike has a fixed gear, and I like to keep
the overall simple aesthetic for the 99% of rides for which I
don't need a light. In other words, I don't commute a lot--mostly
taking the fixie out during daylight hours for enjoyment.

So the trade off (again, for me) is well worth it.

--
Ted Heise West Lafayette, IN, USA
  #38  
Old May 7th 18, 03:07 PM posted to rec.bicycles.tech
Frank Krygowski[_4_]
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Posts: 10,538
Default Dynamo/LED power conditioning

On 5/7/2018 9:43 AM, Theodore Heise 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.


Sure, I get that--and don't disagree. But for me, the effort to
find the light, have a charged battery, and mount it is small. I
keep things in established places, and plan ahead. The risk of
failure is acceptable (to me).

On the other hand, I rarely need the light, and like having the
handlebar real estate available for other things. Also, my
commuter (and beater) bike has a fixed gear, and I like to keep
the overall simple aesthetic for the 99% of rides for which I
don't need a light. In other words, I don't commute a lot--mostly
taking the fixie out during daylight hours for enjoyment.

So the trade off (again, for me) is well worth it.

Sure, YMMV.

About keeping things in established places: I've always been big on
that. Another (ahem) person in this house is much more creative and
spontaneous with her storage, which is why I frequently help her find
things. ;-)

But one good cycling friend of mine lived (before retiring) 1/4 my
distance from where we both worked. He had very low-traffic streets to
get him to work. Yet he always drove, despite frequently bitching about
the lack of parking places. When I asked why not ride the bike, he said
"I have to find the bungee cords to hold my briefcase on the rack, find
my helmet, find the pants clips or change my pants - it takes too much
time."

I thought that was kind of lame. Whatever I need is on my bike, ready to
go. Why not?

But for me, that includes the headlight and taillight.

--
- Frank Krygowski
  #39  
Old May 7th 18, 04:31 PM posted to rec.bicycles.tech
Jeff Liebermann
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Posts: 4,018
Default Dynamo/LED power conditioning

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?



--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
  #40  
Old May 7th 18, 05:05 PM posted to rec.bicycles.tech
Jeff Liebermann
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Posts: 4,018
Default Dynamo/LED power conditioning

On Mon, 7 May 2018 03:46:21 -0000 (UTC), bob prohaska
wrote:

Joerg wrote:
Why should bicycle lighting be inferior to car lighting?


Does anybody make a bicycle dynamo that produces more than 3 watts
at 10 mph?


I couldn't find any, but they might exist. What I found were plenty
that claimed as high as 15 watts, but didn't bother mentioning what
rpm, mph, or kph was required.

How much more power do you need or want?

10 mph = 16 kph
From the graphs:
http://www.myra-simon.com/bike/dynotest.html
at 16 kph, the range of output power is 2.5 to 3.4 watts.

Notice how the power curves all flatten out as the power increases.
This is intentional as it prevents blowing up the incandescent lamp
filament with too much voltage at high speeds. It's one by designing
the dynamo windings so that the core saturates at some load point.
Spin the dynamo faster, and the voltage remains roughly constant. If
you want more power, you'll need both a bigger or stronger magnet, and
either a different grade of steel for the armature or just more steel:
https://en.wikipedia.org/wiki/Electrical_steel

With a hub dynamo, you're kinda stuck with the available products,
most of which max out at 3 watts at 10 mph. You could make something
in a larger hub or just find a SMALL eBike hub motor that can be wired
as a generator or dynamo. Maybe something like this:
https://www.alibaba.com/product-detail/Hot-Sale-24v-36v-48v-The_60740001136.html
but without the internal brake and 3 speed gearing.

With roller or bottle generators that are driven by the tire, all you
need are two generators running in parallel (with isolation diodes if
they are not identical). Double the power, double the output, and
double the drag.


--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
 




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