Nichia & 123 cell?

Can I direct drive a Nichia with a single 123 cell? If so, what would be the approximate runtime? What about multiple LEDs?

You can but it will be dim (underdriven). The Vf is typically around 3.6 volts as I recall so you won't be seeing much current going through the LED. A run time test might put you to sleep. /ubbthreads/images/graemlins/grin.gif

- Don

...Gotta proliferate more of those LiIons... 3.6V... Those guys would pretty much run an LS or Nichia in DD...

Im trying to make a krill/glowtoob type light using a couple nichias,123's, and some acrylic rod. i guess i should use 2 123 cells then and resistor it? What about a very underdriven LS would that be better than a nichia at spec? I want a long runtime (20+ hrs)

Bent Beak /ubbthreads/images/graemlins/smile.gif ,

Yeah, the Li-Ion seem designed around these LED's!

MTFD17,

I just fired a Nichia up that was sitting on the bench and at 3 volts, a whopping 3 mA of current was going through it! You want runtime!

A Luxeon DD on a 123 puts out a nice amount of light but the Vf of the particular LED will really be significant. I compared a L bin to a J bin on a 123 cell and the current going through the L bin was 50 mA and the current going through the J bin was 90 mA.

- Don

A Nichia LED, with a 100 ohm resistor and two 123 lithium in series, will stay lit for 40 hours before start dimming. The dim state will last for another 100 hours (of useless light).

Anthony

Anthony, How much current is going through the two Nichias on a new battery?

As far as Luxeons go - I believe the Red, Orange and Amber luxeons Vf is pretty close to 3.0. I'd bet you could get some nice light and decent runtime out of an Amber.

Jon

To factory specs, a white Nichia must be driven at 30 mA (or 0.03 A), and the Vf (that stands for "Voltage forward biased") across the diode is about 3 Volts. Considering a Voltage of 6 volts, produced from 2 x 123 cell in series, here is where the 100 Ohms comes from:
6 - 3
R = ------------ = 100 Ohm.
0.03
If you want use two nichias, you need two 100 ohm resistors, one in series at each LED.
Hope I have been clear enough... otherwise tell me, I'll post a schetch..

For Luxeon is a totally different story. 1 Watt Luxeons have the same (almost) Vf of Nichias, but they draw from 300 mA to 1500 mA. Especially at high currents, they MUST be mounted on heatsink.

Anthony