Noob needs help with GD board and Cree.

:huh: I have posted this on the Shoppe forum also but can't seem to find any help.

I am looking at the GD500 board and I am trying to learn the techno/lingo.
Vin is from the power source to the led
Vout ? is this out of the board and to the led?
Vf what is this? is it the voltage the led wants to run?

If a Cree XR-e is looking for 350 to 700 mA and 3.6 volts and you feed it with a GD500, what happend when the Vin drops below Vf? Is this were regulation stops? What happens from that point on down until the Vin reaches the cutoff voltage?

With the voltage question being asked. What are some good battery combos for this board? 3XAA/AAA, 2XAA, 1X18650, 2Xcr123?

Can someone point me in the direction of a good post to help explain this. Thanks for the help.

I just posted in your other thread.

So say that the Vf is 3.6 and I start with a 4.5 volt alkaline source. The board will buck. Now as the voltage drops to below 3.6 the board will boost the voltage or the current? Is current always the same and the voltage adjusted? Will the battery reach a point where it just can't be boosted any more? Is this called "out of regulation"?

It shoudl regulate the current to whatever it is and should bosst or buck the input power to achieve a 3.7 volt output. As the voltage drops on the battery there will be more current draw on the batteries so they basically they are going to drain faster progresivly.