UV led flashlight Vf question

Hi everybody,

i am going to build a couple of UV flashlights using the Nichia NSCU033A UV-led. The host is going to be an MTE ssc-P7 flashlight. I would like to run on a single 18650 battery, and if possible a direct drive.

Wich bin is most suitable for this setup, and how wil it perform. I do not want to burn out a led because of there pricetag!
The P7H Vf of 4.0V to 4.4V should give me no problems but wont put out max, is it safe to use the P7M? (3.6V-4.0V)

Here is the datasheet: http://www.nichia.com/specification/led_09/NCSU033AT-E.pdf

Thanx for the advice...

Here is my interpretation of the data.

The datasheet says that the relative power output at 500mA drive current is 1.0, and at 1000mA is 2.0. So that brackets your expected output.

The LED is rated for an absolute max power dissipation of 3.3W, so that dictates (along with Vf) how much the drive current can be.

The graph of "Forward Voltage vs Forward Current" looks like it is close to a Rank M LED. At If~500mA, Vf~3.6V. At If~800mA, Vf~4.0V.

So at Vf~4.0V, the LED dissipates about 3.2W -- basically right at the max. Thus, you probably don't want to go above Vbatt~4.0V.

At Ibatt of less than 1A, the Li-ion shootout data seems to suggest that an 18650 can hold above 3.8V-3.9V for an appreciable amount of time. Even the voltage sag from Vbatt,init of 4.2V down to ~4.0V can take on the order of minutes.

Thus, I would say that Rank H is your safest bet in terms of not frying. Rank M might be somewhat overdriven for a few minutes if you use a fully-charged 18650 hot off the charger, but is probably safe enough also. If you charge your 18650 only to something like 4.1V, Rank M would seem to be safe from being overdriven.

The Rank H would probably be driven at a relative power output of around 1.0 initially, down to 0.75 near the end. the Rank M would start out near 2.0 and drop to 1.0 near the end.

Okay,. so if i don't use the battery fresh of the charger i would be okay using a rank M. I will only use the light for periods under a minute at the same time anyways.

Just out of curiosity, where are you buying these Nichia's? I'd be interested in a couple. (price?) Thanks,

John F

Here in the Netherlands, the price is approx. 110 dollars. If i am going ahead with ordering i would have no problem ordering a couple extra....

i am having star boards printed as we speak, when they are finished i will test the flashlight for my application and wen suitable (will be for sure) i am going to order the leds