1000 Lumen Light at Costco. High/Low/Flash. Spot to Flood Zoom. $20.

On Mon, 20 Oct 2014 19:30:50 -0700, Joe Riel wrote:

Jeff Liebermann writes:
I just love the specs:
36000 candelas is nice, but no clue at what distance it was measured.

You might want to review the definition of a candela. It doesn't depend
on distance. Given a source of 1000 lumens, and assuming a beam of
uniform intensity, the cone angle, theta, from

1000/36000 = 2*Pi*(1-cos(theta))

is approximately 5.4 degrees, less than optimal for most cycling applications.
Presumably it can be spread a bit. Your other concerns seems spot on.

Oops. I looked up the definition before posting, and still managed to
screw it up. Thanks for the correction.

beamwidth = arccos(1 - lum/(cd * 2Pi))
beamwidth = arccos(1 - 1000/(36000 * 6.28))
beamwidth = arccos(1 - 0.004423) = arccos (0.9956)
beamwidth = 5.39 degress

Yep.

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

On Tue, 21 Oct 2014 07:06:17 -0700, sms
wrote:

High: 1.7A
Low: 0.3A
Flash: 0.45A

Hmmm... that's very different from my estimate of 1A in high power.
With 6v of battery, that's 6 watts.

4*1.5V*`1.7A=10.2W.

Oops. Using your measurements, that's correct. Using my guess(tm),
it's not.

So 100 lumens/watt would be close enough for a 1000
lumen claim assuming 95% efficiency for the DC to DC converter which is
not difficult to do.

However, that doesn't explain the 2 hr operating time. To do that,
the battery capacity would need to be:
1.7A * 2hr = 3400 ma-hr
The Duracell alkaline C cell is only rated at 1500 ma-hr. That's why
I guessed 1.0A drain, working backwards from the battery life.

Duracell doesn't exaggerate like some of the
resellers from the Middle Kingdom.

They certainly did exaggerate the battery life. I have a few new
Duracell C cells in the fridge. I'll run a discharge test at 1.7A and
see how long they last. Next posting...

With these LEDs it's all about the
thermal solution; how much heat you can dissipate so the LED doesn't get
so hot that it burns up or unsolders itself from the board.

Or drops in light output. Yep, that's the basic problem. I'm rather
surprised that nobody makes an integrated polished aluminum reflector
that doubles as a heat sink. It would not be an adjustable beam, but
it would ceratinly be cheap.

Sorry, I don't do low power lighting. I want mega-lumens.

You need to re-think your philosophy. "Mega-lumens" are sometimes good
to have in reserve, but in many cases they are not necessary. Your
grandfather did not have mega-lumens.

My grandfathers (in Poland) all rode horses and used kerosene lamps.
Mega-lumens was only achievable with a large fire.

Do you keep your high beams on all the time?

Actually yes. My favored bicycle lamp is a Planet Bike 1 watt light,
which produces 76 lumens:
http://ecom1.planetbike.com/3044.html
I can't see anything in low power and 7 hrs on high is long enough
that I don't worry much about dead (rechargeable) batteries. I will
confess that I don't do much night riding and rarely ride in the rain
or fog, so my experience level is limited. I would be a very poor
prospective customer for my own mega-lumen headlight design.

Why is a larger reflect a good thing? What aspect of bicycle lighting
will benefit from a large reflector?

Look at most commercial bicycle lights and you'll understand.

That is NOT a suitable answer. What part of the light beam would
benefit from a larger reflector? The brightness, beamwidth, spot
size, light distribution across the spot, footprint pattern, side
scatter, efficiency, etc??? About the only thing that a bigger
reflector will do is produce a smaller spot size, which is not exactly
what you want on a bicycle. It won't produce any more lumens as
that's done by the LED, not the reflector.

There is one advantage to a bigger reflector for my design, but it's
not part of this discussion. The larger light gathering power of the
larger reflector will increase the sensitivity of my LED oncoming
headlight detector.

I compared this light against the light my wife had been using, the Life
Gear LG21-70004-BLA.

http://www.ebay.com/itm/111457655946 $71

The new light has four advantages: 1) it's a little
shorter because it doesn't have the rear flasher, even though it's a 4C
rather than a 3C. 2) It is brighter. 3) The beam has no hot spot because
of the lens, 4) spot to flood zoom.

Which one of those features does the larger diameter reflector
benefit?
1) Length of the light depends on the batteries used, not the
reflector.
2) Brightness (lumens) is independent of the reflector.
3) The lack of a hot spot is more about the reflector shape, than the
size. I think you'll find that wider reflectors have a WORSE hot spot
due to their ability to focus the light to a smaller spot size.
4) Zoom is normally accomplished by moving the light source in and out
of the reflector focus. How the beam responds depends on the
reflector shape, not size. For the somewhat hemispherical reflectors
I've played with on adjustable focus lights, I get an annual ring
(donut) shaped pattern, with a dim black hole in the middle.

I've tried to get her to use a smaller light but she says that for part
of her ride, on a multi-use path, she likes a flashlight that can be
used as a baton.

Now, there's the real reason. It can make a better weapon. The C
battery would be the correct diameter for a woman. The crenulated
light shield rim around the reflector should do some real damage. The
ridge ahead of the on/off button looks almost like the hand guard on a
sword. It even has a decorative pommel. A true light saber.

I haven't looked at them as bicycle lights, but there is a large
selection of "tactical" flashlights available.

She was in the army and she can cripple an attacker
with a baton. She also has been tempted to use it on cars. So today I
gave her the new light. The old light also has a lens that's a little
scratched so I ordered a replacement but it will take a while to arrive.

I can guess who wins domestic arguments.

So walk over to Costco today and upgrade from that Maglite.

Ride over to Costco. It's a bit far to walk when I'm carrying
something. The bicycle works nicely. However, the Costco light is a
downgrade from my 3D Maglite. Real men use D cell size flashlights as
weapons, and not puny C cell lights.

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

For your reference, records indicate that
sms wrote:

On 10/20/2014 7:32 PM, Jeff Liebermann wrote:

Sorry, I don't do low power lighting. I want mega-lumens.

You need to re-think your philosophy. "Mega-lumens" are sometimes good
to have in reserve, but in many cases they are not necessary. Your
grandfather did not have mega-lumens. Do you keep your high beams on all
the time?

Back 10 years ago, before LEDs were very powerful, I was thinking about
how something as power-thrifty as a 5mW laser could be used to light a
path. You could, and still can, project a grid out much farther than
conventional lighting. It doesn’t allow you to exactly “see� things, but
it does give you a sense of what objects are in the environment, especially
at distances that otherwise require “mega-lumens�. A more sophisticated
system could be built that actually paints the edges of objects around
you, sort of like a live laser light show (but continuous illumination by
laser is pretty much a non-starter these days).

--
"Also . . . I can kill you with my brain."
River Tam, Trash, Firefly

On 21/10/2014 17:58, Jeff Liebermann wrote:
That is NOT a suitable answer. What part of the light beam would
benefit from a larger reflector? The brightness, beamwidth, spot
size, light distribution across the spot, footprint pattern, side
scatter, efficiency, etc??? About the only thing that a bigger
reflector will do is produce a smaller spot size, which is not exactly
what you want on a bicycle. It won't produce any more lumens as
that's done by the LED, not the reflector.

A bigger reflector, if designed appropriately, increases the size of the
light visible to those looking at it, and hence reduces dazzle. I much
prefer having cars with larger headlamps coming towards me rather than
smaller. But it would almost certainly be a fairly tricky design.

I suspect the reflector on the IQ lamps is that size for packaging
reasons (nobody wants a great clumpy light).

On 10/21/2014 9:58 AM, Jeff Liebermann wrote:

However, that doesn't explain the 2 hr operating time. To do that,
the battery capacity would need to be:
1.7A * 2hr = 3400 ma-hr
The Duracell alkaline C cell is only rated at 1500 ma-hr. That's why
I guessed 1.0A drain, working backwards from the battery life.

Where did you see 1500mAH? I see from 7000-7750mAH.

http://www.alliedelec.com/search/productdetail.aspx?SKU=70149223

The thing is that Alkaline batteries really don't like such a high
discharge rate.

On 10/20/2014 7:32 PM, Jeff Liebermann wrote:
On Mon, 20 Oct 2014 18:27:59 -0700, sms
wrote:

You were not the person I was thinking of.

Sniff. I'm crushed, but will eventually recover.

Buy milk at Walgreen's. Best
price for Berkeley Farms milk. Buy other dairy at TJ's. I SPIT on Safeway!

Safeway is convenient. That which doesn't kill or bankrupt me, keeps
me going.

You can use NiMH C cells.

One of these perhaps?
http://www.candlepowerforums.com/vb/showthread.php?287461-Eneloop-C-amp-D-Cells-Exposed

No, I would get the low-discharge actual C cells which are 4000mAH. They
are more expensive than AA cells in a C adapter but they are much higher
capacity than the AA cells.

http://www.all-battery.com/centura-cardnimhC4000mahrechargeablehighcapacitybatteries1 0207.aspx

You can also buy non-low-self-discharge C cells which are higher
capacity, i.e.
http://www.all-battery.com/TenergyPremiumCSize5000mAhNiMHRechargeableBatterie s4pcs-90418.aspx

A regular Alkaline C cell is around 7000mAH so they last longer than the
NiMH batteries but I think with people being so used to charging all
their devices that this is no big deal.

I just wish that it could be charged internally.

On Tue, 21 Oct 2014 09:58:16 -0700, Jeff Liebermann
wrote:

So 100 lumens/watt would be close enough for a 1000
lumen claim assuming 95% efficiency for the DC to DC converter which is
not difficult to do.

However, that doesn't explain the 2 hr operating time. To do that,
the battery capacity would need to be:
1.7A * 2hr = 3400 ma-hr
The Duracell alkaline C cell is only rated at 1500 ma-hr. That's why
I guessed 1.0A drain, working backwards from the battery life.

Duracell doesn't exaggerate like some of the
resellers from the Middle Kingdom.

They certainly did exaggerate the battery life. I have a few new
Duracell C cells in the fridge. I'll run a discharge test at 1.7A and
see how long they last. Next posting...

It's worse than I thought. When I ran the test, the CBA II informed
me that the recommended discharge current for an alkaline C cell is
0.75A. I'm testing a 1.7A. The results were disgusting:
http://802.11junk.com/jeffl/alkaline/Duracell C MN1400.jpg
(Run 1 on graph) The battery voltage dropped instantly from 1.5V to
about 1.2V and slowly dribbled down to 1.1V with a measured capacity
of 115 ma-hr.

I thought the problem might be my fixture, so a continued the test
(run 2) with the same partly discharged battery. I also dropped the
dropout threshold from 1.1V to 1.0V This time, it went to 200 ma-hr.
I then checked for voltage drops across any of the connections and
found that it's not the reason for the low voltage measurements.

There didn't seem to be a knee on the graph, so I decided to lower the
dropout point to 0.5V and run it again (run 3) on the same battery.
This time, there was a knee at about 1400 ma-hr. Add that to the
previous 2 discharge tests, and the battery capacity is probably good
for:
115 + 200 + 1400 = approx 1700 ma-hr.

However, that's at 0.7V, not 1.5V. Instead of 10 watts, the 4
batteries might deliver at end of life:
4 * 0.7v * 1.7A = 4.8 watts
assuming the built in inverter will run at 0.7v. It will be at full
brightness near EOL because it is still drawing a constant current of
1.7A. (LED's prefer constant current drivers).

So, it looks like the C cell can deliver 1700 ma-hrs and will run for:
1700 ma-hr / 1.7A = 60 minutes
not 2 hrs, but only if the built in inverter will work down to 0.7VDC
input voltage.

Duracell C battery data sheet:
http://ww2.duracell.com/media/en-US/pdf/gtcl/Product_Data_Sheet/NA_DATASHEETS/MN1400_US_CT.pdf

It's not too late to take the flashlight back to Costco and buy
something that runs on 18650 batteries (if you can find a decent 18650
battery).

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

On 21/10/2014 19:58, Jeff Liebermann wrote:

So, it looks like the C cell can deliver 1700 ma-hrs and will run for:
1700 ma-hr / 1.7A = 60 minutes
not 2 hrs, but only if the built in inverter will work down to 0.7VDC
input voltage.

The old NiCd C cells were 1.2AH. Have you got some seriously duff cells
there?

On 21/10/2014 20:06, Clive George wrote:
On 21/10/2014 19:58, Jeff Liebermann wrote:

So, it looks like the C cell can deliver 1700 ma-hrs and will run for:
1700 ma-hr / 1.7A = 60 minutes
not 2 hrs, but only if the built in inverter will work down to 0.7VDC
input voltage.

The old NiCd C cells were 1.2AH. Have you got some seriously duff cells
there?

Ok, have now read your datasheet. Wow, that's pretty poor. So using
rechargables for high current applications makes even more sense than
normal.

On Tue, 21 Oct 2014 10:23:06 -0700, sms
wrote:

On 10/21/2014 9:58 AM, Jeff Liebermann wrote:

However, that doesn't explain the 2 hr operating time. To do that,
the battery capacity would need to be:
1.7A * 2hr = 3400 ma-hr
The Duracell alkaline C cell is only rated at 1500 ma-hr. That's why
I guessed 1.0A drain, working backwards from the battery life.

Where did you see 1500mAH? I see from 7000-7750mAH.

From the Duracell alkaline MN1400 data sheet:
http://ww2.duracell.com/media/en-US/pdf/gtcl/Product_Data_Sheet/NA_DATASHEETS/MN1400_US_CT.pdf
constant current graphs based on my original estimate of 1A constant
current drain and 1.0v dropout voltage. For 1.7A and 1.0v, I would
call it 1200 ma-hr. It's rather difficult to extrapolate from the
graphs, so the numbers are probably somewhat inaccurate.

http://www.alliedelec.com/search/productdetail.aspx?SKU=70149223

It points to a different data sheet at:
http://www.alliedelec.com/images/products/datasheets/bm/DURACELL/70149223.pdf
7800 ma-hr using a 10 ohm load (not a constant current load) down to
0.8v dropout voltage. At 1.2V average voltage and 10 ohms, that's
about:
1.2v / 10 = 0.12A = 120 ma
load. Yeah, it might just make it to 7800 ma-hr with such a tiny
load, but we're talking about how well it does at 1700 ma, not 120 ma.
The thing is that Alkaline batteries really don't like such a high
discharge rate.

Yep. Like I said, Duracell flashlights are designed to kill batteries
and sell replacement batteries.


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