/diy/ - Do It Yourself

>>1399123
>utoob comments are retarded
Stop the presses, all of them.

>>1399125
You need to care about the LED's current rating, because the current through the LED increases rapidly (to destructive level) after you exceed its normal operating voltage. It isn't entirely impossible to run LED from a constant voltage source, but the manufacturing tolerances, temperature variation etc. make it usually impractical.

Your resistor isn't a "2 volt" resistor, it is a resistor which drops the extra 2 volts when some suitable current goes through it. You can choose whatever current, as long as it is less than the LED's maximum rating; this controls the brightness.
Another way to see it would be that your LED is a current-driven component and that your resistor converts the 2V voltage difference to drive current.

>>1304570
that'd be interesting, such high-resistance wires
more likely they rely on the Vf vs. If curve of particular LEDs, and to a lesser extent on the internal resistance of the battery for e.g. throwies, Pic related.

>>891213

the major thing to understand about LEDs is that the have a very sharp I-V curve: as you increase the voltage beyond a certain point, the current line shoots almost straight up into self-destruct territory. so, you always wanna regulate the current rather than the voltage, coz each device has a different inflection point.

so you have an If of 9A and a Vf of 3.6V. the simplest way to connect them would be in series, using 2-4 devices. if the power supply has a current limiting function, you set it to, say, 7A, and just crank up the voltage until the current-limiting kicks in (around 14.5V if using 4 devices).

if you dont have current limiting, then the best way is to wire them is in parallel, with each LED having a series power resistor. so, say you set the voltage to 6V, you'd need a 0.33-ohm resistor rated at 25W or better.
R=(6v-3.6v)/7A=0.34ohm,
P=(6v-3.6v)*7A=17W