1-1/4" Sink tube LED tutorial

[YardDog]

If you did a direct drive using the 3.6v lithium ion cells, wouldn't it be better to have them in parallel, then no resistor or buckpuck?

What am I missing?

[Novastar]

Yarddog... first of all, you would likely only need a single Li-Ion cell, seeing as it provides 3.7v of power (4.2v on full charge under no load).

Secondly, you CAN indeed run without a resistor... but you do need to know what you're doing. For a project where the forward voltage of the LED very very closely matches (or is slightly higher) than the 3.7v Li-Ion cell... you're good--you will not likely need a resistor.

However... again... if you DO NOT KNOW what you're doing--always use a resistor. A good example would be a red Luxeon III. It's forward v is around 3v, and 3.7v (or 4.2v) will probably not make it happy... this much voltage will likely destroy it.

Finally, regarding a buckpuck... a puck is generally all about "current driving". In other words--it regulates current. Overall, this is better for an LED. A resistor does NOT regulate current. There are advantages and disadvantages to both... like so many other things in the world.

[YardDog]

Yes, I accept all that as true and good.

My question is really (even though you may not need but a single cell) would it hurt anything if you connected two or more in parallel so as to enjoy longer "bright blade" time? The forward voltage shouldn't change so you should be good to go, right?

I apologize if my original question was muddled.

Oh, and I've seen your site. Good info. Great resource.