Yeah the DC to DC may be a dead end. I knew that DC to AC converter were ineffecient but didnt know DC to DC converters were as well. Can anyone else varify this? If so the only other two options I have is to run it off 2 DVX100 batteries or find a new Lith-Ion battery thats 14V. What a shame. I was really hoping to use just one DVX battery.

I sure hope that a bright (Sic transit ..) manufacturer reads this. There should be basis for some killer producs - an ambrella with build in LEDs for a collapsible softlight. The possibles are very interesting.

rgds

lots of laptop batterie are 14.4v. You could try to find an broken one that just have the battery and the charger still working.

LEDTronics is very specific that the input voltage must not be above 14 VDC. It there is no tolerance above that (I'd believe they have something of a safety factor) then the 14.4 LiONs aren't great.

I have three Sony V-Mount LiIONs for my DSR-300 but they are way out of line with regard to cost. So I'll go with the 12 V LiON pack for $90 (with charger and cables) as the power supply. IT has 4,000 milliamps of capacity which is around 40 hours of light or so. I should have it in hand sometime this week and will report.

What I'd really like to find is some rechargable LiON pancake batteries of about 2" diameter so I could stack them.

Laptop batteries are quite expensive (new) and rarely have a stand-alone charger. Plus they require an enclosure or they are a bit fragile. Plus the issue of making a power connector.

<<<-- Originally posted by Jos Svendsen : I sure hope that a bright (Sic transit ..) manufacturer reads this. There should be basis for some killer producs - an ambrella with build in LEDs for a collapsible softlight. The possibles are very interesting.

rgds -->>>

But you don't need the umbrella, just a set of ribs to hold the LEDs out in a nice pattern. And that's if you don't mind carrying a flat sheet of plastic in which the LEDs are mounted.

BTW, when I pulled the plug on the lamp, it had run for 48 hours on my battery belt. According to the voltage left in the belt, it probably would have run for more than another 24 hours. The LED indicator on the belt had just tripped down to the second green segment.

<<<-- Originally posted by Mike Rehmus : So I'll go with the 12 V LiON pack for $90 (with charger and cables) as the power supply. IT has 4,000 milliamps of capacity -->>>

i use the rayovac nimh 15 minute rechargeable aa batteries to power the in-car camera rig... i believe that they are at least 2,000 mah each, ~1.26 volts, ~$3.50 per battery at walmart.

that's a lot more power, for a lot less money, than you'll ever get with lithium ion... and lithium ion is rated as "Moderate discharge current - not suitable for heavy loads" : http://www.batteryuniversity.com/partone-5.htm

lithium ion may have a slightly better charge density, but it comes at a steep price.

another ~$5(?) in radio shack battery holders, and you can mount those aa's anywhere you want.

using an ampmeter and a voltmeter, i tested several of those nimh in series at a .632 amp drain... they lasted somewhere around an hour before the voltage started dropping significantly, and upwards of two hours before the voltage dropped enuf to threaten shutting down the recorder.

what do you think of these, 100 loose leds?

http://cgi.ebay.com/ws/eBayISAPI.dll...835189145&rd=1

or the semi-truck backup lights. I know these are BRIGHT!

http://cgi.ebay.com/ws/eBayISAPI.dll...488334437&rd=1

im thinking the backup lights are the way to go, you get 2 light modules for a total of 80 lights for 80 bucks! already in a waterproof housing!!!


or a smaller 27x2 led lights
http://cgi.ebay.com/ebaymotors/ws/eB...spagename=WDVW


http://or use these as hair lights<b...category=33713

<<<-- i use the rayovac nimh 15 minute rechargeable aa batteries to power the in-car camera rig... i believe that they are at least 2,000 mah each, ~1.26 volts, ~$3.50 per battery at walmart.

that's a lot more power, for a lot less money, than you'll ever get with lithium ion... and lithium ion is rated as "Moderate discharge current - not suitable for heavy loads" : -->>>

Since the 42 LED lamp draws a measured 79 ma, I don't think I'll have a power discharge issue with the LiON. 4,000 mah (this particular battery) will always beat 2,000 mah, I think.

You will need 10 of the nimh to get to the minimum 12 volts this lamp requires . . . that's $35 and to equal the power density of the LiON, you will need two sets to get as long a run time.

So that's $70 plus you have to purchase the battery holders, make up a cable, and buy a charger which is another $15.00 or so. Except I've not found a charger that will handle 10 batteries at once so you require 2 chargers to keep the batteries up in sets. (assuming you want an equivalent run-time from the lamp)

This LiON comes in an enclosure that is visually nice, not a group of battery holders that themselves need a housing. Charger was included as is a very nice detachable coiled cable to carry the power from the battery to the lamp. I can easily velcro the battery to the handle of my PD150 camera or to the back of the battery, alongside the wireless receiver, on my DSR-300.

Since this rig will be seen by my customers, it is, I think, the best way to go right now.

What I'd like to have is something that is light and contains the lamp and the batteries without adding lots of pounds to the top of the camera. Hence the desire for pancake batteries because they stack so easily.

I'm not against nimh and use them in quite a few applications. They just offered no advantage in this application and they have to be packaged, a significant time consideration.

When you say your in-car rig, what are you powering?

<<<-- Originally posted by John Gaspain : what do you think of these, 100 loose leds?

http://cgi.ebay.com/ws/eBayISAPI.dll...835189145&rd=1

or the semi-truck backup lights. I know these are BRIGHT!

http://cgi.ebay.com/ws/eBayISAPI.dll...488334437&rd=1

im thinking the backup lights are the way to go, you get 2 light modules for a total of 80 lights for 80 bucks! already in a waterproof housing!!! -->>>

The way they get very bright white LEDs is by making the phosphor coating very thin. That does two things:

It drives the color temperature way up because more of the blue LED light 'sneaks' through the phosphor.

The phosphor 'wears out' more quickly since there isn't as much of it.

If a LED is rated at 100,000 hours, the light output at EOL is less than 1/2 the starting output. Unfortunately, the drop off starts fairly early in the life of the LED. The good news is that none of us will probably even get to the start of the drop off curve.

There is a distinct lack of important information about the two items you cite.

- No spectral info other than 'white'
- No disbursion information, e.g., how wide a beam do they create (although the picture of the individual LEDs shows a strong lens which suggests they may have a very narrow beam).

Especially without spectral information, you don't know what you are getting. Can you afford $80 for an experiment? If so, please let us know how they work out.

ya...if I do get em, how can I measure color temperature?

an easy way to drop down voltage is to insert a diode into the line. Usually you loose about 0.7V per diode.
You can find diodes supporting several amps very easily and it cost almost nothing. The only issue is the voltage drop is permanent so when the battery goes low you still loose power when it is unneeded.
The top of the regulation is to use a low-drop regulator.
this is a one chip module that can regulate anything with a 0.5v loss. you just need a resistor to set the voltage you want.
They are usually pretty expensive (about 10-15$ ) and must be mounted on an aluminum cooler, but it is still a cheap solution.
I use some of them to get 12V from my li-ion 14.4 cells.

And they are fairly efficient (although I haven't measured one and don't remember the real numbers.

Color temperature is difficult as a spectraphotometer isn't something we normally have hanging around. They are made but the are expensive.

My DSR-300 gives me the color temperature when I white balance it so that's what I use.

<<<-- Originally posted by Mike Rehmus : 4,000 mah (this particular battery) will always beat 2,000 mah, I think.

You will need 10 of the nimh to get to the minimum 12 volts this lamp requires . . . that's $35 and to equal the power density of the LiON, you will need two sets to get as long a run time.
-->>>

one of us has the math wrong... 10 nimh aa batteries @2,000 mah each = 20,000 mah total; but then again, it's been years since i looked at my dc power formulas!

the power density actually refers to how many mah are in equal-sized physical containers... nimh aa vs. lithium ion aa, for instance... i think that's a win for lithium ion, assuming you can get that technology in aa's.

you are right about the current drain, tho... it's not going to be a problem for lithium ion!

i can get 4 nimh aa's + charger for $28 at walmart... so for $90, i can re-charge my entire 20,000 mah power supply in 15 minutes... you'll never be able to do that with lithium ion! there are also covered aa battery boxes available that will clean up the way things look, but yeah, it all has to be custom-assembled.

i've been looking at doing led lighting for the in-car camera rig... i need to match the interior illumination to the outside... i'm running a sony xc-999 lipstick camera mounted to an i/o port rollbar mount, recording to a full-on 6 mb/s solid state mpeg2 recorder, no videotape at all... i built a stereo pre-amp as well, mounted all that stuff to a custom aluminum rig that zip-ties to the rollbar... i think that it'll stand up to just about any vibration.

actually, if you speak about AA cell, it is only 1.2V, so you need to chain 10 of them to get 12V.
when chaining cells, voltage adds up but current (mA) stay the same. to add current, you need to mount all celes in parallel.
you better need to try 3.6v li-ion elements who offers the best capacity versus weigth/size ration.
unfortunately they requires special chargers.
They are easy to find as you can get them for free from defective Laptop battery packs. Most of these packs have one dead element thar renders them useless for the pc, but once dismantled have still enough value to justify the spending into a li-ion charger.

Alright im gonna take the plunge on some "Backup lights" $80 bucks no biggie. If it doesnt work I'll have some big flashlights. Im gonna go to a truck stop and try to get just one. Im gonna follow smoe truckers around and see what they look like. LOL

on second thought, I may just go buy a Britek...

you guys are right about the batteries in series... i'd have to have 20 of 'em to equal that lithion ion pack... ouch!

i have read that lithium ion has an optimal weight/size ratio, so that 3.6v thing makes sense.

is there a dimmable function to any of this? would the color temp change? maybe you could just turn on or off additional rows of lights instead.

Between their rated 14 and 12 VDV operating voltage, the light does change. But there isn't an output control mechanism that really works other than switching LEDs in and out of the circuit.

The problem with that is that unless the LEDs are set up for diffuse light in the first place, you might notice a 'hole' in the light cast by the fixture. the output from a LED is, depending on the lens (which mainly controls dispersion) molded into the top of the LED, very columnated.

Would not the brightest thing to do (pun not intended) be set up the LEDs in arrays that need a low voltage (i.e., no serializing or only in pairs) and use a voltage regulator circuit?

Ultimately, perhaps. But you cannot get too low as the forward voltage requirements of an LED is 3.5-4 volts. So you could chose to put two of them in series and match the 7.2 volts of a camera LiON battery. Maybe. Not very much voltage margin

But the quickest way to get underway with very limited time is to purchase an array of LEDs already in a lamp housing. Without asking for a special product, the lowest voltage range they offer is 12-14 VDC. Makes sense since so much of the world has 12 volts available.

Furthermore, I have not yet found a reliable source of warm white LEDs and don't want cool white for this application.

Beyond that, you have to decide what style of lens you want on the LEDs otherwise they all seem to come with a very narrow beam disbursion which doesn't work too well for videography.

Finally, this lamp came with all the correct LEDs, matched, tested mounted in a standard fixture and, BTW, bi-polar.

A lot of features for a relatively low cost.

Update - The LiON battery has been powering the LED lamp for over 8 hours now and looks like it would run another 8 to 16 hours before the battery reaches depletion.

Good enough for a town this size.

BTW, the battery weighs just over 12 OZ, is about 6" long by about 1.5 by 1.75 inches in cross section with a 4 LED charge indicator. Its output is switchable in several steps between 3 and 12 volts.

Also came with a very nice leather pouch with a belt clip and D-rings for hanging it from a strap. The pouch also has a pocket for the output power cord. Power cord is a coil-cord and will stretch to about 4 feet or so. Charger appears to be intelligent and is a wall-wart. A cigarette lighter charger was included so one can charge it while in the car.

Now all I have to do is complete the enclosure.

Hey Mike I've tried alot of LED's and even have the same LED panel array you have. Are you sure you want to run off only 12V because the output is much higher at 14V with that light. Try it out before you get to far with the housing.

-Brett Erskine

THe housing won't contain the battery, just the lamp, mount and power connector.

The lamp gives me enough light for use in events. I'll probably gen up a 14 volt supply when I get the time. Just the addition of a AA battery in series with the 12 volt battery just about doubles the light output.

After looking at the prices and sizes of the lap top Lith-Ion batteries I decided to go back to the original design and just do two 7.2V Lith-Ion camera batteries. This way I dont have to buy any new batteries or charger and if I dont use them for the light on some shot i can still use the batteries for the camera. I really wish I could find a "voltage doubler" or DC to DC converter that will make it possible to use only one battery. In the mean time Im looking into ELECTRONIC dimmers so that I can effiecently dim the LED's and do it without changing the color temp. Found a kit but looking for a small ready made unit. Otherwise the case is done and looks real pro. Small, thin and light weight as possible. I'll post pics when I rework it with the new/old battery setup. Anyone else busy on this project? What have you been doing?

Great LED Website and Luxeon Stars
 

I just notice this thread and am also a big fan of LED lighting. I didn't notice anyone post up a link to the led museum: http://www.ledmuseum.org/ The guy who runs this site reviews and tests discreet LEDs and *anything* made with LEDs. It is unbelievably comprehensive, most descreets have detailed info including JPEGs of the led's light thrown on a test pattern so you can see the dispersion and any hot spots.
while you are there check out Luxeon Star emmiters. these are very high output LEDs 1 watt and 5 watt models (yes that's right 1 watt), they are a bit expensive (~$20) but have many advantages over using single Nichias or other regular superbright LEDs
Also, I saw somewhere back in this post someone stating that DC-DC converters were not effecient, this is not absolutely true, there are many new ICs designed specifically for driving LEDs that take lower voltages boost to the optimum voltage and provide current limiting, dimming capabilities (through pulsing), and allow batteries to completely used up, because when the voltage drops too low the LEDs will not light and this happens rather abruptly. I think most of these circuits are designed for small LED pocket lights where battery life is a significant concern. Oh also check out the candlepower forums www.candlepowerforums.com (they have been having some problems as of late with their server) Plasmid

Mark, welcome.

Do you have a reference for the LED DC to DC converter chips?

Hey Mike,
Well about 2 years ago I bought ic's(i think they were the LT1932 from linear technologies, discontinued I think, see the lower link, zetex sc310 seem to be popular now) that I thought were 8pin dip packages but for surface mounting to pc boards they were "thin-sot" super tiny things, about 2mmx3mm but they were only a few bucks a piece, could have gotten some board and fabed out some thing, still might, but I got busy doing other things. I just did a quick peek at the candlepower forums and found the link below, $10 for a luxeon driver using similar chips, mounted on a board and ready to go and 1 watt luxeons for $12. I found it in the "Flashlight electronics -batteries included" subforum. Given you interest in DIY I think you'll really appreciate the LED freaks/DIYers there. Search around and you should be able to find plenty of people selling (or directing you to a retailer) everything you could possibly want to put together some kick-*ss LED lighting, and for sure you should pick up a Luxeon Star, you will not believe how small and bright they are, 164,200 mcd@364 mA, versus 11,700@23 mA for a Nichia NSPW500BS, you standard white led.

Anyway the LED driver ics that I bought are somewhere in my house, I got 5 of them so if I find them I'll send you a couple and then all you have to do is get a thin-sot prototyping board from digikey and a couple parts and you can check them out, if you want. I think it's much easier to just find someone who is selling the assembled boards such as the one below... Also be sure to check out the ledmuseum.org, there is a section for links "where to buy leds" as well as tons of links for everything reviewed on the site! Mark


http://www.quality-items-flashlights.com/product_info.php?products_id=91&XTCsid=c43130f4f8fca8ddc8e2da11e4e42d9e

http://www.linear.com/pub/document.html?pub_type=desn&document=295

Nice links, thanks!

I used the Maxim MAX757 for my prototype with 'regular' 6-8000 mCd LEDs:
http://www.maxim-ic.com/quick_view2...._pk/1167/ln/en
I followed one of their application notes, and set the output voltage through the divider at 3.5V. There are newer ICs available, but they don't come in DIP packages, only surface-mount. The IC worked great, but I've yet to find true white LEDs without the blue tint...

Hey Roman,
looks pretty cool. I was quite surprised when I got the LT1932s, which I knew were surface mount but didn't realize they were the size of surface mount resistors, but with 8 pins to deal with!! the ledmuseum has a lot of color spectrum info, you might find some less blue whites digging around there. Mark

Some of the blue from the blue LED driving the phosphor usually gets through. Worse is the uneven color temperature near the edges of the beam. That cant be filtered away.
A modern halogen bulb is about the same efficiency as the best white LED's. I know it's fun to play with the LED's, but they do have some issues.
What was the main motivation to use LEDs , other than the novelty?
-Les



<<<-- Originally posted by Roman Shafro : Nice links, thanks!
The IC worked great, but I've yet to find true white LEDs without the blue tint... -->>>

<<<-- Originally posted by Les Dit :
A modern halogen bulb is about the same efficiency as the best white LED's. I know it's fun to play with the LED's, but they do have some issues.
What was the main motivation to use LEDs , other than the novelty?
-Les
-->>>
Portability. Though I've never researched halogen, I assumed it's much more power-hungry than LEDs. Are you referring to regular R20-type halos?

I also wanted to use LiIon cells from junked laptop batteries (most of the cells are intact when the battery is disposed of), and those don't like high currents.

Lastly - YEAH, it's COOL! Too cool, almost blue. :D

P.S. Mark, I think I see a good one, ETG-5CEWHT-35, thanks to your links:
http://www.etgtech.com/update/products/through_hole.htm

Do some research on lamp efficiency, white LED's are just as power hungry as modern halogens, for the same amount of light.

Don't assume!

-Les



<<<-- Originally posted by Roman Shafro :
Portability. Though I've never researched halogen, I assumed it's much more power-hungry than LEDs. Are you referring to regular R20-type halos?

I also wanted to use LiIon cells from junked laptop batteries (most of the cells are intact when the battery is disposed of), and those don't like high currents.

Lastly - YEAH, it's COOL! Too cool, almost blue. :D

P.S. Mark, I think I see a good one, ETG-5CEWHT-35, thanks to your links:
http://www.etgtech.com/update/products/through_hole.htm -->>>

Halogens have other downsides including the weight of their support systems, the heat they generate and the relatively low lifetime compared to LEDs (OK, that's a stretch).

LEDs can also be dimmed with no change in color temperature (that matters).

For a lot of my event work, I need a light to fill in the shadows and pop the color. I don't need 100 watts as I used before. 42 LEDs with an incandescent color temperature, all in a MR-16 package that will run for 3 days on a very small LiON battery pack is ideal.

LEDs even count higher in the comparison when I have to get on an airplane to attend an event and I don't have to ship heavy NiCAD battery belts and large lamp setups.

The small on-camera Halogens don't work very well in the event environment (unless one counts something expensive in the $200+ price range.

Another benefit? People like to talk about the LED setups and for me, that's an ice-breaker with some of my subjects.

Mike, As I stated, the Halogens need the same amount of power as the LEDs. So what extra heavy support systems are you needing for them? Not batteries.
Bulb life? Not a factor, unless you are doing CSPAN recording!
Variable power? Use three small halogens, and switch them as needed.
But it's way more fun to play with LED's , I know ;)
-Les

Les. Here's why I made my LED light.

1)Because of LED are laid out in groups they can be both directional light AND soft light at the same time all the while not having to be diffused. Dont have to buy a mini chimera which would have cut down the power of the light quite a bit.

2)Dimmable without color change

3)None of the batteries life is used up to generate heat. Talent looks good and is confortable under the light. No more burned gells.

4)Modern LED's can be tungsten balanced and dont have any color problems at the edge of the beam

5)You no longer need heavy battery belts to run your light. Just your camera's batteries attach right to the back of the light.

6)More compact light. 1 inch thick

7)Lighter weight/One piece system on top of your camera allowing for steadicam work

8)The bulbs can handle shock much much better than halogens and are rated to last 100,000 hrs. If one bulb burns out your not down for the day nor is the shot ruined.

9)Lower amp draw compaired to a halogen

10)The same light could be adapted to work on light stands for a ultra compact light kit that works DC in remote locations or AC on set.


Every light has their pros and cons. Halogen for example will allow you to do spot/flood where LEDS would have to be rigged up differently. Anyways hope that helps.

-Brett Erskine

Even if we agreed that LED's and halogens are the same I guess the question that really matters is who commercially makes a on camera halogen light that:

1)Doesnt have a hotspot
2)Dimmable/No Color Shift
3)As Soft
4)As Small
5)Runs of your camera batteries
6)Not hot
7)etc etc etc.

Please tell me where I can pick one up because I would have rather not gone thru all the trouble of building something that already exists.

Brett,
How are you getting lower amp draw with the LED's ?
Perhaps you don't need as much light ?
They use the same amount of power as properly selected halogens. Same battery weight. Same AC requirements.
Again, LED's are not battery power savers , lumen for lumen.

Maybe the effort in designing and fabing and LED light is more than designing and fabing a good halogen light.
Apples for apples.

Les,
Interesting discussion. I am certainly surprised that halogens are comparable to white LEDs in terms of efficiency. I was just reading that a mini-mag light draws 0.8 watts on fresh batteries, I'll have to find my 1 watt white luxeon star, as I recall it will dimmly light an entire 12X15 ft room when placed up in one corner, I don't believe the same could be said for the mini-mag, but I am going to check. My question to you is, if in fact halogens and LED are basically equivalent why would I want to design a lighting system where I would have to be constantly replacing burned-out bulbs when I could have one that wouldn't, and have the added bonus not having a hot light fixture. I am pretty sure you knowledge of LED technology is rather dated and I'll bet your "properly selected" halogen bulbs are not cheap, however it seems to me, the most versatile and portable lighting system using currently and easily available technology, would probably use both halogen and LED sources together, each for it's strengths. Mark

PS ultimately using hot wires to generate photons is an aging technology all that heat is just wasted energy, LEDs are just begining to find their way into the mainstream as a basic lighting source. the advances in the last couple of years are simply astounding and will continue.

Mark,
I am fairly up to date on LED's. I designed the LED light source for my 35mm film scanner. I also am a bit of a flashlight-a-holic, and have a couple of 1 watt flashlights as well as a 75 watt Xenon short arc, ala Maxabeam.
It surprised me that the halogens are about as efficient as a good white LED.
For a flashlight that gets knocked around a lot, it makes total sense still, plus I like the blue-green light tint my Luxeons give me.
Sure, hot metal wastes a lot of energy in the IR band, but still, they *do* make a lot of usable photons.
It really sucks when old tech, as boring as it is, still does a great job!
One of the big problems with white LEDs is the color unevenness across the field.

Has anyone investigated small cold cathode fluorescent lamps? I know that the normal household 'compact' lamps make probably 2X the light of an LED ( lumens/Watt ) but they are bulky. Maybe the thin long cold cathode ones are better? They are used extensively in laptops. Hmmm, laptops are power critical... and they don't use LED's either!

-Les

Rather than continue with the he said she said heres real world specs of my LED light:

LED Light
Total Wattage Used: 12watts
Light Output: 350fc @ 1 ft
Light Beam Angle: 60 degrees (perfectly even color all the way across the beam)
Operating Temp: 102 degrees physical bulb temp after 1 hr

Please give us link to a halogen bulb that has better specs

Also laptops use fluorescent like bulbs because of what they are lighting up...the screen. The screen needs to be evenly lit from one side to the other. The bulb as the physical characteristics it needs to make that happen. Have you used a micro Kino before?