Another Newbie

Been reading this forum for a little while now, ever since I got my first LED light (a free photon light from a tradeshow) I'm completely hooked. Anyway, I was hoping someone could answer some questions or point me to a site with more informations (Although I've already checked out all the links and homepages from this site) I apologize if these have been answered before, or if it's just common knowledge that I don't know.

1)I kinda know the basics of the circuit diagrams I've seen, the step up, step down stuff, but can someone explain in plain english (not to technical) exactly what these are meant to do?

1a) A step down lowers the voltage to within the required range for a LED, but how does that compare to just using a resistor? does it give longer burn times buy conserving the energy or something?

1b) And does this effect the light intensity curve during the life of the battery? Does it make the light output more consistant by providing a constant current regardless of battery power?

1c) And what does the step up do? I'm assuming it allows you to use more LED's with a given battery,right? but again, does this affect the output during the life of the battery?

2) In terms of rating the flashlights for brightness, how do these compare with a regular maglite AA or 3C cell? the maglites are rated in candle power, how does this compare with mcd? I've read the difference is due to the different ways of measuring (ie sherical output vs directional output of the led) but can someone give me a very general idea of what kind of mcd output would be comparable to these two lights? For example, if I wanted to make an equivilent flashlight for these two, how many Nichia's or Luxeon star's would I need to have a similar flashlight for these two?

3) Does pulsating the flashlight really have any effect on the brightness and battery life?

Alright, that's all for now, I'll save all my other questions for later. Eventually my goal is to make a small to meduim sized flashlight (4AA or AAA size) but use eight of those small 6V or 12V batteries to power it, and have at least six or seven Luxeon Stars (or as many as I can fit) in it. I probably won't get a very long run time, but I'd want it to have a constant light output for the life of the batteries, and be as efficient as possible. Right now, I've got the ability and resources to do it, but not the knowledge.

1)a) Yes, step-down decreases the output voltage without consuming much of the power, as compared to a resistor.

1)b) Yes, it makes the light output consistent until the battery voltage drops down to the output voltage.

1)c) Step-up increases voltage to the required level. For example, an LED needs 3.5V to run, but a single cell can only give you 1.4V. So the step-up draws more current from the battery to bring-up the voltage at the output to 3.5 V.

2)1000 mCd = 1Cd. However, candelas are often misleading, so the best way would be to see a comparison photo of the beams. I hope someone else will give you the numbers, because I'm afraid my estimate could be too inacurate.

3) Pulsating sometimes increases the perceived light output per amount of power used, but it requires square wave to be effective. I don't think anyone uses pulsed current to drive LEDs though.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by InTheDark:
1)I kinda know the basics of the circuit diagrams I've seen, the step up, step down stuff, but can someone explain in plain english (not to technical) exactly what these are meant to do?
<HR></BLOCKQUOTE>

Look at all these step up and step down regulators like at a gear box.

Voltage=RPM and current=torque.

The product of both is power. You have a give volatge from your source (battery) and you need another voltage for your load (LED or incandescent bulb). The power stays the same, minus the losses.
It is pretty easy to incorparate some kind of regulation, so that over a given input voltage the output stays more or less constant. For example the Arc AAA uses a uses a tiny step up circuit which gives a reasonable regulation. While the cells voltage changes over an big range, the LED's current changes only about 1:2 (and the brightness even less). If unregulated it would probably change 1:100 or so.
If you have only few voltage to get rid off, a resistor may have a better efficiency, but offers no regulation at all.
Usual efficiencies for these regulators are from below 50% (especially when boosting from a single cell) to over 90% (with very big effort).

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>
Does pulsating the flashlight really have any effect on the brightness and battery life?
<HR></BLOCKQUOTE>

There is a popular myth that pulsing lights may fool the eye and therefore look brighter than they are. Look at Don Klipstein's web page for an clarification.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by mad_scientist:
2)1000 mCd = 1Cd. However, candelas are often misleading, so the best way would be to see a comparison photo of the beams. I hope someone else will give you the numbers, because I'm afraid my estimate could be too inacurate.
<HR></BLOCKQUOTE>

Photos could be even more misleading, it's better to have both .-)

Maglite 3D = 14,000 CP
Maglite 4C = 14,000 CP

Scorpion = 6,500 CP

****edit: http://www.maglite.com/ website shows Maglite 3D is rated 13,000 PBC (Peak Beam Candlepower).

MAG3D 14,000 CP and Scorpion 6,500 CP were taken from http://www.brightguy.com/.
******

Here are photos of different lightbeams;

http://albums.photopoint.com/j/ViewPhoto?u=443720&a=13143240&p=53795328&f=0

http://albums.photopoint.com/j/ViewPhoto?u=443720&a=13143240&p=50425315&f=0

3 samples of Maglite 3D & 4C lightbeams were photographed from the tightest, medium, widest beam focus of hotspot to the given distance.

All lightbeams were photographed with one camera setup and setting - after selecting from series of sampler photos the closest camera setup and setting to how my eyes see the lightbeams. Photos are not perfect but I think more reliable than the CP numbers given by manufacturers when comparing lightbeams.

Notice how Maglite 3D and 4C are rated at 14,000 CP while Scorpion is rated at 6,500 CP.

The question is how did Maglite measure the two models' (3D & 4C) lightbeams to arrive at 14,000 CP while on the picture and in actual comparison of the two lightbeams with my eyes Scorpion with 6,500 CP seems brighter?

I think the problem is how manufacturers measure brightness of lightbeams? I mean do they look at and measure lightbeam as a whole or just the pinprick part of the hotspot with the most intensity of light? They don't tell us that's why when compared to other flashlights lightbeams our eyes and camera see different.

Suppose I do not have a SL Scorpion to compare lightbeams and just take it that MAG-3D with 14,000 CP is brighter than Scorpion with 6,500 CP? Which is more reliable, the picture or the CP number given by manufacturer?

I agree..... it's better to have both.

- verge -

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by 2d_edge:
Here are photos of different lightbeams;
<HR></BLOCKQUOTE>

Very nice. If you could include a scale at the wall in degrees of the lightbeam?

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>
Photos are not perfect but I think more reliable than the CP numbers given by manufacturers when comparing lightbeams.

I agree..... it's better to have both.
<HR></BLOCKQUOTE>

Not wanting to start the discussion again: I think the problem is that you get different manufacturers data.

If you would take all the peak candela measurements and vice versa we only have different manufacturer's beam photos, I would prefer your measurements .-)

Beeing curious: How do you verify that your batterie's state is compareable?

For example a Petzl light which runs on 3AA cells for 3:45 hours until it's completely dead, goes down from 100% to 50% initial brightness in it's first 22 minutes. It is pretty the same with all incandescent flashlights, C and D cells are even worse.

(Verge, can you please start a new topic about these things? I think you have so much to tell.)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by PeLu:
Beeing curious: How do you verify that your batterie's state is compareable? <HR></BLOCKQUOTE>

I rely on the state of unused unpacked fresh batch of batteries. Batteries were used only once with every flashlight with every shot of camera and the reason I do series of sampler photos first - using fresh batteries for every shot - to select the best camera setting. That was how I end up with a small bag almost full of slightly used batteries.

I did measure initial volt of batteries with DMM and they registered above the 1.5v and 3.0 volts as rated. I do not know at what volt level is battery considered factory fresh? Were they 1.590 to 1.600 volts for a 1.5 volt battery and 3.100 to 3.200 volts for a 3.0 volt battery?

I agree with your suggestion from other topic thread to use a regulated power supply for a controlled and measurable power input from a percieved lightbeam brightness.

My problem is I do not know how much volt and current to input using a regulated power supply to a flashlight knowing that even fresh batteries varies in voltage readings with DMM.

Suggestions will be of great help and much appreciated.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by PeLu:
(Verge, can you please start a new topic about these things? I think you have so much to tell.) <HR></BLOCKQUOTE>

There is one already and I don't have much more to say from what I have previously said that manufacturers got to agree on how to test, measure, and rate flashlight lightbeams to avoid confusing the consumers.

Candle Power vs Lumens, whats the difference?

I am learning so much from you and I'm thankfull for that. I'm wondering if flashlight manufacturers presumably already know what you know (standard to measure lightbeam) how come we still have this;

Maglite 3D = 13,000 PBC (Peak Beam Candela) according to http://www.maglite.com/product_anatomy.asp?psc=3DCELL

Scorpion = 6,500 CP according to http://www.streamlight.com/2001/scorpion_specifications.htm

I tend to agree with another CPF member when he said;

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Since the beam qualities of flashlights vary radically, meaningful comparisons based on factory specifications cannot be made.
<HR></BLOCKQUOTE>

- verge -

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by 2d_edge:

Beeing curious: How do you verify that your batterie's state is compareable?
------
I rely on the state of unused unpacked fresh batch of batteries. Batteries were used only once with every flashlight with every shot of camera and the reason I do series of sampler photos first - using fresh batteries for every shot - to select the best camera setting. That was how I end up with a small bag almost full of slightly used batteries.
<HR></BLOCKQUOTE>

I think this is more than enough what you can do for your kind of testing. And open circuit voltage is not so important. It is voltage under load which is interesting(I think they are much closer there, but I actually have to try that on a batch of current alkalines, batteries have much improve since I made my last test runs).

And BTW, can you explain me what a 'candlepower' is? I'm only familiar with candela (European education and so on). I'm not shure if it is the same. There was a unit 'candle' which is slightly more (1.02 cd). Is candlepower luminous intensity?

(And I'm familiar with Hefnerkerzen (Hefner candles), as all my gas mantle lights are rated in it)

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by PeLu:
And BTW, can you explain me what a 'candlepower' is? I'm only familiar with candela (European education and so on). I'm not shure if it is the same. There was a unit 'candle' which is slightly more (1.02 cd). Is candlepower luminous intensity?

(And I'm familiar with Hefnerkerzen (Hefner candles), as all my gas mantle lights are rated in it)<HR></BLOCKQUOTE>

I think that question is better directed to the manufacturers because they're the ones placing the CP rating on their product.

- verge -