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I was working on the 3 dot system and then see that its an parallel circuit so all the leds (the osram's one) will have the same voltage (for me it was 3 v) and then it cross my mind that meaby with another AAA batery and in a serie circuit i will not need resistor, so here is my question:

Why dont build up a serie circuit better than a parallel one???

Dont know if i'm saying some kind of impossible just because i dont know to much electronic but what i use  was the next formula:

R= [Vps- (Nº leds * Vleds)]/Iled=[4.5-(3*1.5)]/.1=0
So in this way i will not need any resistor, did i?

PD---> Maybe i forget a lot of english's grammar and spelling, but it's even worse with my french

That could work w/o resistor but its better to put 1 small value
to protect leds)

Hello rurikvan

As already told in some places in this forum    ,

it's dangerous to operate leds without resistors   .

Leds are basically diodes, not light bulbs (which are basically resistors).

A led doesn't have a linear voltage/current ratio, so you can't just "guess" the current in your led from the voltage you put on its leads.

You need to use a voltage/current graph, and :
- it's specific to each diode model
- it has a rather steep curve

So a small voltage variation can lead to a big current variation, if current isn't limited by something.

This something is your resistor  

Since the resistor will drop your voltage value, seen from the led side, you need to have a power supply voltage a bit higher than the total led voltage drop of your setting.


BTW : don't worry and use the led wizard, its easy and works well. You'll find it on the website front page.


Cya

Even if your power source seems to supply the perfect voltage: add a small resistor for limiting current, the voltage drop on your LEDs will be small.

and about serial vs. parallel: serial should be better if possible, even if it is just because you don't have to convert as much power into heat in your resistors as in a parallel setup.