Parallel or series set up for multi LEDs?

If u were to drive a large number or LEDs say 6 or more for 2 seperate set ups, one set up running on batteries and another running on mains.

Which of the following would be better for each situiation and why?

1. Wired in parallel with current regulator.

or

2. Wired in parallel with voltage regulator

or

3. Wired in series with current regulator.

never in parallel!
why?
a very minor change in Voltage means a high change in current through the led. Then there are also some variations in forward voltage with each led. Now if there were one with a very low fv, this one would get much more current, maybe too much.
all in series --> each gets the same current.

PS: voltage/current regulator ends in the same: ideal situation for the leds = not too much current.

PPS: always plan and check placing, the more leds the stranger problems with shortings and such occur.

yellow said:

never in parallel!

Click to expand...

you should reword it as never Parallel stand-alone

you can use parallel banks of series, it just depends on whats the input power is

yellow said:

never in parallel!
why?
a very minor change in Voltage means a high change in current through the led. Then there are also some variations in forward voltage with each led. Now if there were one with a very low fv, this one would get much more current, maybe too much.
all in series --> each gets the same current.

PS: voltage/current regulator ends in the same: ideal situation for the leds = not too much current.

PPS: always plan and check placing, the more leds the stranger problems with shortings and such occur.

Click to expand...

please excuse the dumb question, but, how do i measure the forward voltage of an led with a digital multimeter? ive definately had that problem before. if the vf of all the leds is the same, then is parallel ok? im powering a 2 cree bike light with an 18650 direct drive, and i dont think theres any way for me to avoid using parallel leds right now. one is a little brighter than the other.

#3 series with a current regulator.
cause that would cover for Vf changes, and in Series you have higher voltage and less amperage, with less amperage the Parts to regulate will be having less heat problems.
often (but not always) its easier to regulate a higher voltage to a series string than trying to push so many amps through any single component.

also all conversion from one voltage to another of any sort costs efficinecy, so if your on wall power, you have a lot of original voltage, easier to work at/with higher voltages. if your working with 12V battery, best to have the leds be close to the 12v in some way, be it bucked or boosted. if your working with 1.2v single cells, then its better to have a 1.2v led less conversions of any type are better efficiencies.

this is one of them "do as i say" opinions, because i have used all 6 methods, series&parellel both, high amps, high volts, voltage regulated, current controlled, pulse width modulation, resistered, adjustable resistered, hard wired, series only and parellel only, and they all have basically worked. even AC worked , but that had to be the WORST.

Personally, I think series is best. Parallel is workable, with either an individual series resistor for each LED in a non-regulated light, or an individual current regulator for each LED in a regulated light. But, I would suggest never, ever, using one single current regulator upstream of parallel LED's. In a parallel circuit, the sum of all the branch currents must equal the total, and since the regulator locks the total to a fixed quantity, any LED that decides to draw more current than its neighbors will steal current from them. Worse still, if any LED's decide to draw less current than their neighbors, the regulator will ram the difference down the throats of the others to keep the current constant.

please excuse the dumb question, but, how do i measure the forward voltage of an led with a digital multimeter? ive definately had that problem before. if the vf of all the leds is the same, then is parallel ok? im powering a 2 cree bike light with an 18650 direct drive, and i dont think theres any way for me to avoid using parallel leds right now. one is a little brighter than the other.

Click to expand...

I dont think the vf of any leds can be this even.
Your example of the 2 with one seeming a bit brighter states that. I would guess (but have no clue at all) with 2 "equal" emitters running at the same time and showing different outputs, the difference is at least a 10 % as our eye is not too god at that (gets even worse when the 2 dont run at the same time). Current diff will be higher.

By now I do not know of a very good method of using a single li-ion, just flupic or direct drive (I do have a flupic light and some to these boards for others here. There simply is no other board as far as I know).
A "2 in series" with a step-up regulator (something from the shoppe, Shark or Badboy f.e.?) will ensure same current to both and thus (almost) equal brightness.

But if You hook them in direct drive with a resistor for each emitter, You might get the current/output equal with different resistors. Just place one setup in series with a DC-meter, connect both to batt and check readings. Do this for both and eventually change resistors.

I've built three tri lux lights in 3D Mag hosts... Parallel wired on 3 alkaline cells. I sold the two Lux III lights and kept the one I did with R-bin Lux Is. I've probably put 200 hours on it and nothing too odd has happened. I did a lot of playing with different samples of stars trying to get a good balance of 'white' and good outdoor color rendition. I've ended up with two RW0Hs and one RV1H. The seem equally bright, but who knows.

I guess my take is this. If you are going to put decent money into the project (ie, Crees or SSCs or certainly Lux Vs) and a dedicated host, then yeah, I'd probably current regulate it. I got my Lux I LEDs out of several Elements from Sam's Club, I bought several and sold the ones without the bins I wanted, and I already had the Mag host and the only things I really had to 'pay for' were the PTS heatsink, three IMS reflectors and a UCL Lens. Discounting my time and maybe a little gas money, I have probably $30 or $35 in real money in the light.

If you have $35 in a light and you get 200 hours use out of it, who cares if one of the LED degrades a few percent faster than the others? On the other hand, if you are having Milky put multiple Crees in a Surefire host, then sure... current regulate that bad boy.