Safe method to test my crees?

[Lynx_Arc]

HERE Is a thread about the Cree Q4. I am guessing the Vf of the q5 will be slightly lower and the output perhaps 5-10% more so
I am guessing at 350ma you will get about 120 lumens out of a q5 by the charts that is perhaps the output of a ~10-20 watt incan bulb?

ok I am guessing 3.4v is needed so 3nimh is charged about 4.2v so you need to drop 0.8v at 350ma.
using ohms law E=IR or R=E/I we get 0.8/0.35 or 2.3 ohms. using P=IE (watts law) P (power in watts) is 0.8x0.35 or .28 watts... a half watt resistor I think should suffice at that level. I am rather tired so if my math is off don't get too upset
try a 5 ohm then work down to a 2 ohm with the 10A ammeter inline while going. if the current exceeds the 350ma by much your Vf may be lower or batteries could have more charge voltage.

 

[boxy]

Thank you lynx, go get some sleep.

I can wait. what i really need is a constant current driver delivering a tiny number of mah per led over 3 rooms. just how many requires a little testing.

Boxy

 

[Lighthouse one]

Why don't you get 2 of the led lights that plug into a usb? Or you could get a zebralight headlamp..I use one to read.

 

[boxy]

Why don't you get 2 of the led lights that plug into a usb? Or you could get a zebralight headlamp..I use one to read

I already have a drawer full of crappy old style led lights. (using 5mm leds)

I am trying to build a high efficiency-low power system cause my female partner in (not) crime is fed up with my hatred of and frequent failures of mains lights. Thus my purchase of ten cree xre q5's. Previous to my posting here, (and hi everyone, thanks for the great information library btw) I had hoped i could continue my old technique of using 12v with many strings of 5mm leds along with many tiny resistors. Now after buying crees and reflectors i find that probably wasnt the most intelligent goal, and i am confused how constant current drivers work. Ive read many threads...

Q. Do cc drivers deliver for example 1000ma of current over the whole of a 3 cree string. OR does a 1000ma cc driver deliver 1000ma to each led in the string?

Q. If i want to drive 10 cree's at 100ma each, how can i make this practical as the whole string would require 37 volts Vf?

should i give up this simple approach and buy lots of smaller drivers, allowing the driver voltage to be 11.1-14.4V? (yes i use automotive conventions)

the whole area of drivers is so full of questions, and ive read literally a hundred or so threads over the last few months.

if i want to drive from 12v it seems likely that my best bet is 10 buck drivers at the lowest ma i can find? or should i be considering 5v as thats closer to the nonbucked vf?

sigh. previous to this i thought i was a technically adept person.

Boxy