CREE MCE question mA and vf

I've been doing some research for LEDs for my next bike light and was looking at the Cree MCE 370 lumen one. Its listed on the Cree site with a vf of 3.9V but 12.8V on LED Supply. Anyone know whats the real vf? I suspect 12.8V

As well if this is running at 350mA as indicated in the specs producing 370 lumens does that mean a battery pack with say 3000 mAh would last upwards of 8.5hrs or is my math out to lunch?

What I'm trying to do is come up with a light that puts out at least 200 lumens and consumes as little power as possible - need it for ultra distance road events.

The MC-E has four individual die, the connections of which are all available to the user. This means you can connect all four die in parallel (~3.5V), all four in series (~14V) or 2 series 2 parallel (2s2p) for ~7V. You can choose the configuration best for you.

BillyNoMates,

Thanks. I've been working on single die lights so far.

If I connect them in parallel do I still get the same light output just 4xthe mA usage at ~3.5v?

Versus in series I suspect I get a higher voltage draw and the same low 350 mAh.

Am I correct on this?

I guess another benefit is I can put a separate switch on one or more dies so I can control the light output that way.

POH,

you are correct in your assumptions, the parallel wiring ups the amps, while the series connection requires more voltage to trip the Vf's added together.
The question is: what kind of battery do you have and what type of driver are you plannig to use with the LED?
The constant current drivers operate best when the die are connected serially, because then the preset amps flow through all of them. If you connected a constant current driver to a parallel wired MC-E and then cut the connection to some of the die, the remaining ones would be fried unless you chose a low enough current setting... and that would be a very expensive mistake

Nemozoli thanks for setting me straight.

I planned on running this on a 4xAA 6V rig and would carry 2 or 3 of these as I need to be able to get batteries anywhere in the event I run low on power while on an event.

So what I hear is that I should put them in series then if I use this power source I need a booster to power them. Either that or change the power source to a higher voltage one such as a 8xAA 12V rig.

In series though the 350 mA would be the draw of all 4 dies correct?

yes. So look at Taskled's drivers (or the driver rundown, which is here somewhere) and check out that at 7.2V - 6 x NiMH - you could easily run all four in series at 500mA+ and still not break anything.

What's the application?

Bret

bretti_kivi its for a road bike light. I've make DiNotte style lights before and this will likely be the same. Need something that run for long periods on a small battery pack - Lithium 1.5v or Ni-MH 1.2v depending on what is available.

If I can crank out 200 or so lumens at 350 mAh then I would be more than happy. I can always use a MaxFex driver and if needed crank it up to 500 mAh or higher if the need were there. This is my main interest in the MC-E as it appears to have high lumen output and relatively low mAh usage.

... which is exactly what I had in mind, too.

a Maxflex should see you OK with 12V or 9V of NiMH, so a pack of 8 or so; if you were to use 4/3A, you should see an awful lot of runtime with mass of around 500g. Considering current of 500mA, 4000 mAh and minimal losses, you should be fine for several hours.
I worked this out recently for 6 x 4/3A and got to 1.4A current draw, 10.2W input and therefore something like 2.5 hours at full power. Reducing power will increase battery life. 6 x 67g --> just under 400g for the batteries.
If you get a bin M, you should be able to hit 750 lumens@700mA, and around 430@350mA.

Bret

Bretti Kivi, what optic where you going to use? The only tri emmiter I have found is a 25degree model from luxeonstar.com and a narrow hexagonal one from luxeonstar.com

I'm thinking the 25 degree one is too wide for a road bike. The hexagonal one is a little on the big side for a DiNotte style light though I could make some other shaped housing such as a square.

yes, they are. I was thinking also for a colleague and he wants 10 degrees. I think that's reasonable. He cycles every day to work, and in the winter that means six months of dark riding. I'll be building a triple R2 cree for him over the summer, probably with a fatman and a 9.6V pack.

There's an optic from Fraen with 34.5mm OD and 13.5 degrees; that should be a very good start. I'll be using my MC-Es with stippled and OP reflectors in Maglites, and I want more flood, less throw.

Work out the maths: If you're doing 25km/h, you're hitting 7m/s. Therefore a throw of 15m gives 2seconds worth of warning. I'd have to check the formulas for light distribution, but 20 degrees for localised flood - left and right of the handlebars - and 5 to 10 for throw seems very reasonable.
the 13 degrees should give around a 2m wide circle of light at 10m. According to carclo, this may well already have the four-chip projection - it's easier to find a 60mm 3degree optic for a Lux K2 for throw - here: http://carclo-optics.co.uk/catalog/documents/Lumileds-01-09.pdf - and then use the MCE for flood.

How fast / how far do you want / need to see?

You may well need to build one of these and test it before you can really tell how usable it will be....

Bret

Bretti Kivi,

I think that a throw of 15m is adequate as if things are nasty or fast decents I can turn on my 3 degree Luxeon K2 light to punch up the light out further.

Depends on the terrain and if there is any ambient light.

Thanks for the link to carclo I had not seen the 20mm rebel tri optic. I think this might do the job for me.

I agree I will likely need to build one and see how the output is like to see if I like it.

Its ok I figured it out - just needed to think it through as to how the circuit was connected.

Just out of interest, I'm looking at building a 5x rebel using the penta optic from Ledil: http://www.ledil.fi/datasheets/DataSheet_RER-5-M.pdf

The 12 degree width is not great for throw, but it is good for general riding, plenty of light available on full power from the 5 rebels tends to make up for the relatively wide beam.

I keep promising to post details on this, but I am still working on the housing -its nearly finished, but I want to make a reasonable job on this so I'm not rushing.....

BillyNoMates, 5xRebel would certainly soak the ground with light.

I hadn't seen this optic before for the Luxeon Rebel - 12 degrees is not too bad for throw. Is this for off-road use?

I checked out their other optics and I like the square CNC version as its 21.6mmx21.6mm - something I can easily get square tube for.

One of the reasons I was looking at the MC-E (was well as a rebel tri-emmitter) is that they draw low mAh and I am considering doing up a dynamo-based rig for my roadie. Reading Martin's/Ktronik/znomit/etc posts have gotten me interested in going this route

All this madness started with me doing some research for a bike light for an upcoming 400km Brevet and now I have started a twisted side hobby of making lights (on my second 200lm Dinotte-style).

The Luxeon Rebels are an interesting LED and I can get them local (luxeonstar.com) - shipping and duty charges suck here in Canada.


BillyNoMates - when you finish things up I'd like to see the light!

Hi POH

I've also used the square optic as part of a 3x3 array. See this thread (but don't laugh too much at the rubbish build quality...this is the main reason why I'm taking more time over this next one..)
https://www.candlepowerforums.com/threads/221016

Despite its looks, this light has seen me through the winter, but this is not one I'd like to run from a dynamo - it takes 20W on full power, although I do most of my road riding on third power ~7W.

The 5x rebel will be about 12 to 15W on full, and 3 or 4W on third power. What power is available from your dynamo rig? I haven't read the posts about the dynamo power (I'll go and do that now......), but I would have thought that a multi-emitter several hundred lumen light would create a reasonable amout of drag...

1st: there is no real difference between a Cree XR-E (or a Seoul P4, in theory) and a MC-E ... when they run on the same power (what You are planning, btw.).
But the MC-E gives a wider beam - good for slow speed trail riding in brush, bad for road racing.

As a plus, Your "200 Lumen" is the output of most all single die Led-lights at full power.


imho there is not a single reason using a MC-E is a need here.
You are used to work with single die emitters, You only need the output of one of them, You need more of a focused beam, ...,

How about a good 18650 light and changing cells?
With a 500 mAh draw there is also nice light and about 5 hours of light with a single cell.
(Thats what I lent around a few times last year for 24 hour races. The guy liked it very much)


PS: I use my 200 Lumen light for trail riding and it is usually brighter than most other lights ppl bring along. For road riding I would even power the thing down, when "ultralong" is a must

PPS: Your batt pack ...
take an MC-E in series @ 350 mA.
with a 6 V pack ... current draw of ~800 mA at pack
12 V pack ... draw of 400-450 at pack
(just very rough but speedy guesses!)

BillyNoMates, nothing wrong with your first light. I consider the first light I made my proto-type to prove things out. Yours has a lot of LED's - must be really bright on full power.

I don't have a dynamo rig yet - just trying to prove out the idea to see if I want to venture there and it looks promising. I just blew a K2 LED while working on a circuit so I'll have to replace that before I do anymore tinkering.



Yellow, Good points on the MC-E. I started to look at that at the Luxeon Rebel Tri-LEDs as they have a high output at 350mAh. My reasoning was if I had a lower mAh then the battery (if I'm using a battery pack) would last longer. Or if I use a dynamo, lets say a 6V 500mA one will power it provided I use either a boost LED Driver or a voltager doubler like Martin's.

I agree I need a focused beam. I am using a 3 degree and 6 degree beam now and they have a good throw that gives me around 15m. I suspect using single LEDs may be more ideal. I like the K2's I have used. If I put 2 K2 LEDs in series and run it off a 6V 500mA dynamo + boost driver or voltage doubler then I would problably be fine as that would give me 200 lm. Put the same light on a battery pack and I can crank it to 400lm.

I haven't had any experience with 18650 cells - can't find a retailer locally so I have started looking at other options. My fallback will be to use multiple battery packs and just switch them when they are nearing empty.

The 2 200lm lights I run currently run on 4xAA cells (NiMh or Lithium primaries). I guess if I find a lith-ion reseller locally I can always use 2x18650 and put a voltage regulator in the connection to drop the voltage if I needed to.

Thanks for the pointers on the mAh draw at 6V and 12V - makes sense what you put down.