Re: For those who believe in electricity

On Fri, 11 Apr 2025 11:04:00 +0200, Rolf Mantel
<news@hartig-mantel.de> wrote:

Am 11.04.2025 um 03:56 schrieb Jeff Liebermann:

On Wed, 9 Apr 2025 12:35:15 +0200, Rolf Mantel <news@hartig-mantel.de>
wrote:
 

Am 08.04.2025 um 22:12 schrieb sms:

On 4/7/2025 5:15 PM, Jeff Liebermann wrote:

>

Not going below 0V is the most common way PWM is used.  However, it's
not mandatory or the only way:
<https://en.wikipedia.org/wiki/Pulse-width_modulation>
Note that the waveform shown goes below 0V.

Yeah, that is true, it's possible for PWM to go below zero, but that's
not the way it's normally used for LED light dimming or PWM fan speed
control.
>
With LED bicycle lights, it's surprising that no bicycle light company
has a dynamo input into their battery powered lights. Even at only 3W
from the dynamo, you could power a high-end bicycle light at lower
power, and you could be charging the battery during daytime rides when
all you have on is the daytime running light.

>
"No" is a not quite correct, "extremely rare" would describe the market
better.
<https://nabendynamo.de/produkte/scheinwerfer/ladelux/>
>
Slightly more common: a "dynamo driven power supply" produces power to a
USE output, and theoretially you can route that USB power into your bikt
light but with no fine-tuned optimization the output is too low to make
it worthwhile in any sense.

 
This article shows 26 such bicycle USB chargers.  That seems to be a
popular use for bicycle dynamos.
<https://www.cyclingabout.com/list-of-hub-dynamo-power-supplies-for-usb-devices/>

>
Sure, it's common to use a bike dynamo to charge low-power devices.

I keep seeing advertisements showing a smartphone on the handlebars,
with the backlighting at full brightness, and running some kind of
bicycle related performance, mapping or GPS application.  With a 3
watt dynamo, that's not going to work well. 

Does anyone want me to grind the numbers and calculate the runtime for
various configurations?  It's easy to do, but I'm short on time for a
few more days (or weeks).

Charging mobile phones barely works because many phones stop charging on
a variable power supply.
>
I have no direct knowledge of anybody using a dynamo to top up their
battery lights.

I also have no knowledge of anyone using such a device.  If dynamo
powered USB chargers were so rare, then the device manufacturers need
to improve their market research before releasing products that nobody
will buy.

The CyclingAbout article also mentions installing a buffer battery to
extend the operating time of dynamo powered lights:
<https://www.cyclingabout.com/buffer-batteries-pass-through-charging-dynamo-hub-systems/>
I usually ask myself what problem the manufacturer is trying to solve.
By adding a buffer battery, it's probably (my guess) that the rider is
not moving fast enough to provide enough power for a dynamo powered
light, or that a super-capacitor doesn't store enough energy
(watt-hrs) to be useful on short rides. 

I tend to have each of my devices (smartphone, eWatch, front bicycle
light, rear bicycle light, bicycle computer(?), etc with their own
individual batteries.  The problem is that they all take different
batteries and the only thing they have in common is that they can be
charged with USB.  I haven't done this for many years, but if I were
to ride with the gadgets I have today, I would need a junk bag full of
AAA, AA, 18650, A123, and CR2032 or CR2016 coin cells.  Except for the
coin cells, all of these a LiIon rechargeable cells.



--
Jeff Liebermann                 jeffl@cruzio.com
PO Box 272      http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
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