drop in question

[degarb]

http://www.dealextreme.com/details.dx/sku.14413

Anyone know how many lumen this light would push at 6 volt with resistor to 400 to 600 milliamps

 

[old4570]

http://www.dealextreme.com/details.dx/sku.14413

Anyone know how many lumen this light would push at 6 volt with resistor to 400 to 600 milliamps

Ok lets work from 12Watts ... Your talking 3.6W which is just under 1/3rd ...[ 600mA @ 6v ]

 

[Justin Case]

http://www.dealextreme.com/details.dx/sku.14413

Anyone know how many lumen this light would push at 6 volt with resistor to 400 to 600 milliamps

What do you mean by "push at 6V with resistor to 400 to 600 milliamps"? I don't think that this is a direct drive module, so why would you want to use a resistor? Are you planning to implement a low mode by using a resistor? If so, you have to drop the driver out of regulation into direct drive to do that. That means dropping below the claimed 3.6V lower input voltage figure.

If you feed 6V to the module (e.g., 2x123A), according to the specs the driver will be in regulation and thus feed 2.8A to the P7 (700mA per core).

 

[Justin Case]

Ok lets work from 12Watts ... Your talking 3.6W which is just under 1/3rd ...[ 600mA @ 6v ]

But the 600mA@6V V-I pair doesn't make sense since the module's driver should be running in regulation at 6V. Thus, it should draw more than 600mA from the batteries. If the current draw were only 600mA, then input voltage wouldn't be 6V.

From the basic relationship:

driver efficiency * Vbatt * Ibatt = Vf * If

we can get a ballpark estimate of what Ibatt would be for Vbatt=6V. Assume a driver efficiency of 80% and Vf=3.5V@700mA per core (2.8A total). Then

Ibatt = (3.5*2.8)/(0.8*6.0) ~ 2A.

To get a tail current value of 600mA, you'd have to drive the module in direct drive by using a resistor value that drops the driver out of regulation. Feeding 600mA to a P7 means nominally 150mA per core, which might give you about 200 lumens.

 

[kosPap]

well Justin you cannot be wrong, but I would like to add that in my experience most DX frivers run at below 80% efficiency....down to 60% for the "keenan" 3.9-14V versions

 

[Justin Case]

Sure, driver efficiencies can be all over the map. The driver in the DX6090 seems to be about 65%-70% efficient. But a KD driver I have is near 90% efficient. Regardless, if efficiency is less than the assumed 80%, then Ibatt is even greater than the originally estimated 2A@Vbatt=6V. And that's the point. Ibatt isn't going to be 600mA@6V.