Thinking Outside The Box

On 3/13/2012 2:41 PM, AMuzi wrote:

That's just silly.
Of course we sell German B+M lights, just like everyone else.

How many bicycle shops in the U.S. do you think sell them? Your shop,
and Harris Cyclery come to mind. You'd be hard pressed to ever find
dynamo lights of any brand in most U.S. shops, other than dynamo lights
as part of a very limited number of bicycles.

In fact you're much more likely to find el-cheapo dynamo lights for sale
in a variety store or drug store. I picked up a 12V dynamo light set at
Rite-Aid because I wanted the dynamo, not for the actual horrid lights
that were included.

On 3/13/2012 12:48 PM, Peter Cole wrote:

Many of the reviewers of the particular light I bought said they found
the beam too narrow.

That's a testament to the optics because the big problem with LED lights
is that it's difficult to do anything but a flood beam especially as
power levels go up. I was talking to a marketing manager at a high power
LED manufacturer (Bridgelux in Livermore) about their customer base.
Widely used as replacements for flood lighting, but not for spot beams.

I can believe that, but the spreader made a
substantial difference. The spot is pretty artifact free, while the
spill has slight vertical bars from the cylindrical lenses. I don't
think it will suffer from the "tunnel vision" effect, nor do I think it
will be irritating, provided I keep the spot out of other's eyes, which
is pretty easy with a head mount, the acid test being when you encounter
another person on a 4' bike path.

Even with a handlebar mount, the tilt angle should be set so it's more
of a low beam. There's no purpose in illuminating the sky.

On 3/13/2012 12:25 PM, Peter Cole wrote:

snip

I hear you, but my days of hacking LED lights may be over. I mounted one
(3W MR-16) on a gooseneck to use as a reading light. It came out very
slick indeed, but I spent one whole frickin' day on it. Not efficient,
not when I can get the whole shebang (bike light) for under $40. I'd
wire my dynamo to a Lion charger and be done with it, even if I had to
breadboard the electronics. Anything beats metal work.

Fortunately you can buy something like
http://www.dealextreme.com/p/3w-3-led-270-lumen-waterproof-flood-light-projection-warm-white-lamp-12v-47572
and not have to deal with any metal work. Works fine directly off of a
dynamo. Very easy to mount and wire.

On Mar 13, 1:47 pm, James wrote:
On 14/03/12 06:18, Peter Cole wrote:



On 3/12/2012 9:12 PM, James wrote:
On 13/03/12 10:44, Peter Cole wrote:

The beam shape is conical, the intensity is what it is, but the
efficiency usually isn't state of the art, they're not all that cheap
(compared to other power LED devices), they're much larger than they
need to be, mounting is problematic and they're not weather tight
generally.

Another reason I don't like the idea of electronics on a bike. The
record to date is that lights are generally poorly sealed. My headlight,
which is 4 CREE LEDs with lenses arranged as a full bridge rectifier,
uses no weather protection at all. It may corrode in a heavy salt
environment, granted, but I can spray water on it all day and it
continues to work just fine. Interconnecting wires are 1mm enamel coated.

I dropped one of my battery powered LED lights off the boat one night in
about 10 feet of salt water. It was cheerfully shining on the bottom as
I sadly rowed away.

I turned my rear blinkie on, removed the cover and dropped it into rain
water. It blinked a little faster, but resumed normal operation once I
shook the drips off.

This is not the case for all blinkies though. I've seen others that
just give up the ghost when they get wet. It is likely the switch that
gets fouled.

The deal for water proofing lights is mostly to keep the reflectors &
lenses from fogging. I had another LED light that didn't react well to
being soaked with brake fluid -- the lens got distorted. LED lights
aren't nearly as delicate as cell phones.

Cell phones don't often suffer quite the same conditions of vibration,
heating, cooling, dirt and moisture.


This is my major beef with the PB headlights I use (have not had a
problem with water getting inside my PB taillights). *Both* of my PB
headlights (Blaze 1 and 2-watt) have gotten water inside. The 1-watt
is merely perpetually fogged. The 2-watt actually malfuntioned
(badly) and wouldn't stay in the selected mode of operation one dark
morning - switching itself between modes - including "off".*

They sort of *attempt* to seal it, such that once water gets in it
doesn't drain or even evaporate out, and I had to semi-destructively
disassemble it to get it dried out and working again. After that I
stretched Saran wrap over the leaky part, finishing off with electical
tape, and it has handled rain without incident since (so far). But
that is just ridiculous for a $60 bike light to fail (or even to
suffer perpetual fogging) merely as a result of being used in the
rain.

The 1-watt was impressive - the 2-watt much more so - in terms of
light to see by in such a small, self-contained package with adequate
run time.

(* Note to Frank: This headlight failure irritated me greatly [the
$60 price tag didn't help], and I probably cursed PB up one side and
down the other, but it was no kind of "Oh ****, whatever will I do
now" hand wringing moment, and I rode on just fine. You may recall
that I commuted in darkness *without* a headlight for a time.)

On 3/13/2012 2:40 PM, James wrote:

I don't give a **** where they are made! You now change your tack to one
of market protection.

You may not care, but B&M cares very much. The antiquated German laws
regarding battery powered lights serve B&M very well.

On 3/13/2012 5:00 PM, James wrote:
On 14/03/12 03:25, Peter Cole wrote:
On 3/12/2012 11:42 PM, Ralph Barone wrote:
Peter wrote:

No, it's typically a switching regulator, which modulates duty cycle,
AKA PWM.

The use of a switching regulator does not necessarily result in the LED
being switched ON and OFF at a high rate.

I think it does, by definition.


I haven't analyzed any, so I
can't comment on how many bike light current regulators PWM the LED,
versus
more sophisticated control methods.

As an EE, I can't think of any more "sophisticated" method, unless
you're modulating it to send data or something. FWIW, I've designed a
few PWM circuits for lamp (arc) control, a few switching power supply
regulators and a motor controller or 2.


Then consider a constant current source implemented as a buck converter
where the inductor current doesn't fall to zero.

The average current is kept constant by PWM, and the current is never
zero. It's operating in continuous conduction mode.


I'm not sure what point you're attempting to make.

On 3/13/2012 5:21 PM, James wrote:
On 14/03/12 04:49, Peter Cole wrote:
On 3/13/2012 12:59 AM, James wrote:
On 13/03/12 14:42, Ralph Barone wrote:
Peter wrote:
On 3/12/2012 5:50 AM, Phil W Lee wrote:
Jeff considered Sun, 11 Mar 2012
16:09:07 -0700 the perfect time to write:

If you're referring to my mention of PWM in bicycle lighting, that
was
verified by me with several LED flashlights and one Bike Planet
bicycle headlight. At such power levels, one would need to be a
masochist to use a linear regulator (except in retrofit flashlight
bulbs). Would you like me to post an oscilloscope photo?

So based on your analysis of ONE bicycle light, you assert that all
use PWM?
Why on earth would they?
All you need is a current limiting device, which is typically a
resistor,

No, it's typically a switching regulator, which modulates duty cycle,
AKA PWM.

The use of a switching regulator does not necessarily result in the LED
being switched ON and OFF at a high rate. I haven't analyzed any, so I
can't comment on how many bike light current regulators PWM the LED,
versus
more sophisticated control methods.

You're on the money. It depends on the DC-DC converter topology, but the
current may be continuous and not cause the LED to turn off at all.

See here, page 6 shows the current through the inductor is continuous.

http://www.ti.com/lit/ds/symlink/lm3405.pdf

The same circuit _can_ be used to flash or dim the LED, by toggling the
enable/dim input pin.


From the linked data sheet:

"The LM3405 is a PWM, current-mode control switching buck
regulator designed to provide a simple, high efficiency solution
for driving LEDs with a preset switching frequency of
1.6MHz."


snip

All of this doesn't change the fact that even though the current through
the LED & inductor is a sawtooth, the voltage is modulated on & off, AKA
PWM.

I never disputed the fact that the current is controlled via PWM. I
dispute the claim that the LED is turned on and off. It is not, because
the current through the inductor, as you noted, is a saw tooth, that
never reaches zero (or anything like it) through each cycle.


You are splitting hairs finer than I can follow.

On 3/13/2012 5:47 PM, James wrote:
On 14/03/12 06:18, Peter Cole wrote:
On 3/12/2012 9:12 PM, James wrote:
On 13/03/12 10:44, Peter Cole wrote:

The beam shape is conical, the intensity is what it is, but the
efficiency usually isn't state of the art, they're not all that cheap
(compared to other power LED devices), they're much larger than they
need to be, mounting is problematic and they're not weather tight
generally.


Another reason I don't like the idea of electronics on a bike. The
record to date is that lights are generally poorly sealed. My headlight,
which is 4 CREE LEDs with lenses arranged as a full bridge rectifier,
uses no weather protection at all. It may corrode in a heavy salt
environment, granted, but I can spray water on it all day and it
continues to work just fine. Interconnecting wires are 1mm enamel
coated.


I dropped one of my battery powered LED lights off the boat one night in
about 10 feet of salt water. It was cheerfully shining on the bottom as
I sadly rowed away.

I turned my rear blinkie on, removed the cover and dropped it into rain
water. It blinked a little faster, but resumed normal operation once I
shook the drips off.

This is not the case for all blinkies though. I've seen others that just
give up the ghost when they get wet. It is likely the switch that gets
fouled.

The deal for water proofing lights is mostly to keep the reflectors &
lenses from fogging. I had another LED light that didn't react well to
being soaked with brake fluid -- the lens got distorted. LED lights
aren't nearly as delicate as cell phones.

Cell phones don't often suffer quite the same conditions of vibration,
heating, cooling, dirt and moisture.


You obviously don't have teenagers.

On 14/03/12 14:09, Peter Cole wrote:
On 3/13/2012 5:00 PM, James wrote:
On 14/03/12 03:25, Peter Cole wrote:
On 3/12/2012 11:42 PM, Ralph Barone wrote:
Peter wrote:

No, it's typically a switching regulator, which modulates duty cycle,
AKA PWM.

The use of a switching regulator does not necessarily result in the LED
being switched ON and OFF at a high rate.

I think it does, by definition.


I haven't analyzed any, so I
can't comment on how many bike light current regulators PWM the LED,
versus
more sophisticated control methods.

As an EE, I can't think of any more "sophisticated" method, unless
you're modulating it to send data or something. FWIW, I've designed a
few PWM circuits for lamp (arc) control, a few switching power supply
regulators and a motor controller or 2.


Then consider a constant current source implemented as a buck converter
where the inductor current doesn't fall to zero.

The average current is kept constant by PWM, and the current is never
zero. It's operating in continuous conduction mode.


I'm not sure what point you're attempting to make.

It appears that in the quoted conversation above, you believe that "by
definition" the use of a switching regulator results in the LED being
switched ON and OFF at a high rate.

If that is what you meant, you are incorrect.

--
JS.

On 3/13/2012 6:25 PM, SMS wrote:
On 3/13/2012 12:25 PM, Peter Cole wrote:

snip

I hear you, but my days of hacking LED lights may be over. I mounted one
(3W MR-16) on a gooseneck to use as a reading light. It came out very
slick indeed, but I spent one whole frickin' day on it. Not efficient,
not when I can get the whole shebang (bike light) for under $40. I'd
wire my dynamo to a Lion charger and be done with it, even if I had to
breadboard the electronics. Anything beats metal work.

Fortunately you can buy something like
http://www.dealextreme.com/p/3w-3-led-270-lumen-waterproof-flood-light-projection-warm-white-lamp-12v-47572
and not have to deal with any metal work. Works fine directly off of a
dynamo. Very easy to mount and wire.

Yes, I've seen those, but I couldn't think of a use for them.