dat2zip converters with 3vin

i'm looking for a converter, and i would like to be able to run either a 1w or a 5w with the same converter.

i have seen people using the bb750's or bb700's for 1watt luxeons...what kind of current is delivered at 3vin? also, what is the current delivered to a 5w at 3vin?

also, what is the difference between the 700 and the 750? obviously the 50ma, but that shouldn't make that big of a brightness jump...is there something else to it?

an urgent answer would be greatly appreciated, because i would like to get this stuff ordered tonight /ubbthreads/images/graemlins/smile.gif

Roth,

The bad boys are boost circuits so your Voltage of your battery needs to be below the Vf of the LED. The closer the Vin is to Vf, the less the circuit will have to boost the output and the happier it will be. The BB's can drive both 1 and 5W's at the set current specified but they need to be powered by batteries up to the task. A single 123 cell is capable of something over 2 watts of power but will not provide the 5 watts of power you are seeking with a 5W. The 700bb and 750bb are just that and the 50 mA of output current IS the only difference. 50 mA of current won't make that big of difference in brightness but if you are after all the photons you can get and don't mind powering a bit beyond spec or the resulting chip in run time..........

- Don

Asuming the 3volts vin can take high current draws (say 2 sets of 2AA in parallel, would the BB750 be able to power a 5 watt load at 750ma? How about a 10 watt? Can it handle the super high current intake?

dat2zip responded to a question I had earlier about the same thing. It sounds like you want to get as close to 6v in as possible. It was suggested that 2x123 could manage a 5w w/ his 700 and 750ma board, but not 2xAA (I would assume 2x2xAA wouldn't cut it either). The BB500 board draws over 800ma from fresh batteries, I'd expect the BB700 to draw well over 1 amp and probably a lot more if it's only got 3v coming in...

If you do try it please let us know how it goes.

A rough estimation is to keep the input current under 1.5A, otherwise the Badboy falls out of regulation.

For a 5W Luxeon, that would be approx 6.8V and say 700mA which is 4.76W. Assuming 100% efficiency 3V input would require 4.76W / 3V = 1.58A. As you can see this would not meet the regulators requirements.

For the 5W, the Badboy falls out of regulation around 4V. Anthing below this and the Badboy won't keep regulation. It will still put out and seriously light the LED, just not at full power.

You can run the same calculations for a 1W and different output current settings to get a similar feel if the Badboy will regulate or not.


Wayne

Would the 1.5A input current be because of the circuit design or the circuit's heat dissipation or something else?

thanks guys...i guess i will have to stick with 1w's for now. /ubbthreads/images/graemlins/frown.gif

i suppose there is nothing in the works for a 123 driven 5w?

If you found a solution it would either under drive the 5W or give VERY limited run times. The circuit would have to suck 1.6amps from the 123 to give 5w (assuming 100% efficiency) and those little suckers are only good for about 1.2 amp hours. I'm not expert, I'm probably wrong, but that's my take on it.

ArcMania was considering a step up circuit that was 1.5 vIn (single N-cell actually) but it would really under drive the 5w LS at less than 2.5 watts I believe.

Jon

The magic 1.5A is a circuit design constraint. That's an approximate number and the actual number is a more complex formula.

Wayne

Hey, new here but already hooked. (I've bought parts from 3 members in as many weeks!) Anyway, I've got an idea. Please shoot holes in it if anyone thinks it will not work.

I want to take a D-cell mag light, use 3 123's in ElektroLumens 123 to D holder (which i just got in the mail a couple of days ago. Nice part). Use a BB 750, limit the Vin with a ?resistor? to that magic 6.8v or so depending on the Vf of the LED. And heat sink the crap out of it. Topped with a nice 5W, EKL's 30mm optic and Flashlightlens.com's UCL lens.

Anybody think this might work?

Wayne, the heart of this puppy is your board, so your opinion carries a lot of weight!

Thanks.

[ QUOTE ]
Snewt1 said:
Hey, new here but already hooked. (I've bought parts from 3 members in as many weeks!) Anyway, I've got an idea. Please shoot holes in it if anyone thinks it will not work.

I want to take a D-cell mag light, use 3 123's in ElektroLumens 123 to D holder (which i just got in the mail a couple of days ago. Nice part). Use a BB 750, limit the Vi with a ?resistor? to that magic 6.8v or so depending on the Vf of the LED. And heat sink the crap out of it. Topped with a nice 5W, EKL's 30mm optic and Flashlightlens.com's UCL lens.

Anybody think this might work?

Wayne, the heart of this puppy is your board, so your opinion carries a lot of weight!

Thanks.

[/ QUOTE ]
vIn isn't supposed to exceep VF? lol are my terms correct? with 9v your better off using a resistor to drop the voltage.

My feeling is the D to 123 converter is just a stopgap til the D to 3AA converters are ready. The point of 123's is to get a small light, and putting them in a D barrel defeats that purpose. Better to use AA NiMH and save on battery costs and throw away less old batteries. If you want to use 123's, I think it makes more sense to start with a suitable Surefire or Streamlight barrel rather than using a D barrel.

When the D to 3AA's come out, I'm sure I'll get some. But for now this works. As far as size of barrel, surface area for heat sink.
Thanks for the input though, other's opinions are why I finally got around to registering and posting. (been reading anonymously for a while).

boy...i sure wouldn't mine a 4 to d... /ubbthreads/images/graemlins/grin.gif