Cree MCE driver help

[Djedgar]

I would like to put together a single Cree MCE bike light and not sure of which driver to use. I am a street rider and probably would spend most time at lower levels but do want to run full when needed. I am leaning towards the bflex with ma max current steps at 350, 500, 750 and 1000.

The MCE seems rated at 700ma tops. Is 750ma close enough not to cause problems? (would run the dies in series)

If I read the new bflex specs right, it can drive 25V and the MCE forward voltage appears to be 3.4V for each die at 700ma (total for the 4 dies comes to 13.6V) plus one for the driver gives 14.6V total. If driving at 750ma I would expect that figure would be maybe 15V. Does this sound reasonable?

I am no pro at electronics but know enough to get me in trouble sometimes so hope someone with more knowledge can steer me straight if I am off.

Any other drivers worth looking at? I thought of the fatman. Seems you can trim the R1 to 9.37K to limit it to 700ma. Adding a 50K logrithmic pot gives me further dimming then.

I can set up my battery supply to fit the driver so no worries there.

Thanks in advance.

 

[dnlwthrn]

I'm planning on driving mine with a Fatman, mainly because I have one already. I was going just put in a resistor to knock the power down to 300-350mA for a low beam, and then use the 700mA for high beam. This is going to be a helmet mounted light to pair with my triple Q5 bar mounted light, so I'm going to be using a pretty tight optic on the MC-E, and have a 20 deg in the bar light right now. Haven't received the emitter or optic yet, so I won't have any results for a while.

 

[trout]

I'm going to be using a pretty tight optic on the MC-E, and have a 20 deg in the bar light right now. Haven't received the emitter or optic yet, so I won't have any results for a while.

What optic have you ordered

 

[dnlwthrn]

It was the Carclo "plain tight" in 26.5mm dia from Cutter... Hoping it will work well for helmet. If not, I'll go probably try some others. I was going to get a 20mm optic, but for some reason the part numbers weren't available when I ordered. I just checked again now, and everything is there...

 

[Djedgar]

Thanks for the responses so far. Good idea on the fatman with going to a fixed resistor instead of the pot. Can thus just switch it in or out to dim rather than fumbling with rotating a pot (but then you are fixed at one dim level).

Nobody has addressed if the blex 750ma setting would be too much for the MCE which appears to have a 700ma top. Is the difference of any concern or am I asking for trouble? I realize heat sinking probably plays a big part in this too.

 

[trout]

Thanks for the responses so far. Good idea on the fatman with going to a fixed resistor instead of the pot. Can thus just switch it in or out to dim rather than fumbling with rotating a pot (but then you are fixed at one dim level).

Nobody has addressed if the blex 750ma setting would be too much for the MCE which appears to have a 700ma top. Is the difference of any concern or am I asking for trouble? I realize heat sinking probably plays a big part in this too.

In my opinion the heatsinking is more important than the extra 50ma
I plan to use a Bflex for my helmet light also .

 

[Jarl]

Nobody has addressed if the blex 750ma setting would be too much for the MCE which appears to have a 700ma top. Is the difference of any concern or am I asking for trouble? I realize heat sinking probably plays a big part in this too.

+/-50ma is nothing. P7's have been driven at 6A without turning angry blue, DEFT works with a single die emitter driven at 1.5A with (hopefully) no ill effects, etc. etc. I'd say we'll see keen lumenwhores driving these in series at 1A+ before long, possibly even at about 1.4A. As long as you have the best heatsink path possible (lowest thermal resistance and largest area possible at every junction) then you'll be fine.

 

[Djedgar]

Yeah, I was thinking +50ma was no big deal but I am fairly new at putting lights together. I am going to go ahead with the bflex in my build and look forward to the fun.

Thanks all for the advice.

 

[Momato]

A guy on MTBR is running an MC-E @1000 mA without problems so far.

 

[yellow]

You do not give the info MOST IMPORTANT, or - maybe - dont think about it,
but the 1st step is: to think of WHAT BATTERY You want to use.
From there all the other calcs are made, not the other way round.

except for the taskled-drivers, there is another one: the Sandwich Shoppe SHARK.

All of them have a LIMIT of driving current going INTO the driver, all need heatsinking.
imho, iirc, the taskled "only" can give 2A (+ sinking good), the Shark around 4 A (which I am not sure and would try to evade)

If You are running from a 7.2 V Li-Ion Camcorder batt, drive current should be under the limit of 2 Amperes (we are talking of 800-900 mAh to the series driven Led) ;-)
... all of the step-up drivers should work.

Other cell number:
Problem with any step-ups (in my soldering carrer, dunno what caused possible probs): number of cells (Li-Ion) has to be different from number of led in series.
The usual 14.4 V (4-cell) pack offers a voltage range from slightly over to slightly under the Voltage the led need --> step-up to step-down.
I have not used taskled drivers so far, but in general, this does not work good.
Maybe they can do this, maybe not. Better do not plan a 4-cell pack with the 4-cell led.

Adding a 50K logrithmic pot gives me further dimming then.

which is the way like to set the levels with the shark.
But a poti is useless (never sure what current is consumed, not even near it),
better make fixed levels with a switch that gives path to a few resistor levels - probably a rotary 4-way switch (thats how I set such lights up)