Running 5 Cree Q2(serial) with 14 AA

[rizky_p]

I am planning to run 5 Cree mod inside Mag D head in serial configuration with 14 Sanyo 2700. what resistor value do i need to push them at 1A and at the same time limit the current? 1 ohm 5watt resistor, it is enough?

thanks.

 

[Bimmerboy]

I'm curious as well.

With approx. 17V of battery power under load, would that even be enough to drive 1A through 5 Cree's without any resistor? The total Vf would be higher than Vbatt at that current.

Rizky - You likely need a boost driver to accomplish this.

More thoughts on this from anyone?

 

[rizky_p]

Honestly i am totaly confused. In order to drive 5 Cree @1A does the current need to be 5A? or just 1A since the load which is Cree are in series.

 

[Bimmerboy]

Just 1A is needed. In series you add the LED's voltages together, and parallel you add current.

For example, if each of 5 Cree's in series had a vF of say, 3.7V at 1A, the total Vf would be 18.5V, but the total current needed would remain at 1A.

However, 14 NiMH under load gives approx. 16.8V. The LED's may light up, but they probably won't run super bright... not pulling anywhere near 1A. Thus, a boost circuit would be needed.

I'm taking a totally wild guess, but I think your Vbatt may push them at around 300 - 350mA or so completely direct drive (again, wild guess, no math involved).

Edit: do NOT take my word on the direct drive current. My electronics knowledge is quite rudimentary, and I may be wrong. Wouldn't want you to start frying 5 Cree's... at least not all at once.

 

[rizky_p]

[deleted] reply to wrong forum

 

[bobski]

Edit: do NOT take my word on the direct drive current. My electronics knowledge is quite rudimentary, and I may be wrong. Wouldn't want you to start frying 5 Cree's... at least not all at once.

You got it right. Current is a measure of the number of electrons flowing past a point in a conductor in a given period of time. Following the law of conservation of matter, electrons cannot be generated or simply disappear. Further, electrons don't really compress or pile up unless exposed to an opposite charge like in a capacitor. That means there's pretty much a fixed number of electrons in your circuit assembly and they're confined to running around the circuit.
As such, in a simple series circuit, 1 amp (or whatever) worth of electrons flowing through any given component means there must be 1 amp flowing through all the components.