Adding Foc to PC2

[Elim Vos]

Greeting all,
I've decided to add foc to an older PCv2 with a Pex.
The Led is a Dr/Dr/warm White from luxeon. The deep reds are wired in parallel and white for foc.
My question is are my calculations correct?

7.4V battery, 3.4fv @700mA
Requires a 6.8ohm 3.3watt resistor
If my calculations are correct(double checked the luxeon chart and ledwizard) please let me know.
Or can I use a smaller ohm 3.3watt resistor?

[QUI-GON JINN]

Using a smaller ohm resistor may cause your white led to pop under blade lockup,  you can go higher,  but not lower than what you calculated.  Just an observation here,  but when I used the pc 2.0 in builds with tri-leds,  I always put the two for the blade color in series to conserve battery life.  They will draw less current that way,  especially since you're using a 7.4v pack.

[Elim Vos]

So I'll have to find that size. I know TCSS does not carry them and I didn't find one at RS, so I'll have to search mouser....

Thanks for the response Qui-Gon.


E

[rabbitdragon]

someone else can verify but my understanding is you can push white leds to 1000ma without much issue especially if you are using it for FOC which will help you find resistor easier to fit for you build.  So it is 4.7w 4.7 ohm and TCSS has the 5w 4.7 ohm.

[Elim Vos]

As I read the luxeon chart I can push it to 1000mA.
I think I saw one at RS, I can pic it up tomorrow.

[QUI-GON JINN]

someone else can verify but my understanding is you can push white leds to 1000ma without much issue especially if you are using it for FOC which will help you find resistor easier to fit for you build.  So it is 4.7w 4.7 ohm and TCSS has the 5w 4.7 ohm.

this is correct,  you can drive it at 1000ma...I missed what you were driving it at earlier,  sorry.

[clahey83]

not related to the flash on clash issue, but is there a reason you are running your main LEDs in parallel? since you have a 7.4V setup, you should be able to run them in series without losing any brightness and you will gain quite a bit of run time on your batteries.

[Elim Vos]

Is the drawback for writing it parallel shorter run time and loss of brightness?

Since they are basically getting the same 700mA, wouldn't they 've just as bright? And if I wire in series wouldn't the first get the full 700mA and the second not be as bright?

This is the first time I've worked with a set up like this, I'm used to a tri-Cree RGrB with CeX.

[clahey83]

when you run them in parallel they will split the amps and have the same voltage. so if you are setting the constant current driver to 700 then they are actually getting 350mA each. to drive them fully you would need to set the driver to  1400mA (1.4 amps)
i wouldnt drive red rebels too far over 700, they're not as forgiving as crees

if they are in series (daisy chained) they will share the amps but split the voltage. your voltage from the batteries is high enough to handle them in series, so you can run both off of the same amps.

in short, in parallel to drive them at full potential you would need 1.4A, while driving them in series at full potential you would only need 700mA

[Elim Vos]

Okay, that is a great explanation. I will be sure to rewire them that way. And the 4.7ohm 5w won't give me any problems @ 1000mA?


Thank you guys for the info and advise,

Elim

[clahey83]

that should work perfectly

[Elim Vos]

Alright, I just got the resistor connected and it works great. I'm about to adjust the settings and rewire the main In series.
The resistor is bigger then the Pex.



E

[PhoenixJedi]

Yes, and the deep reds can actually handle 1000mA each... If they're in series set your driver to 1000mA. If they're in parallel set them to 2000.