Multiple LED's. In series or parralel?

[smoguzbenjamin]

Hey all

I got some block-LEDs from a friend the other day, they're like 8 LEDs stuck in one hunk of plastic.  But do I wire 'em in parralel or series? I would guess series because of the voltage drop, but I ain't sure. What should I do before I fry 'em? :?

[Paul Perry (Frostwave)]

Whichever way you wire them, don't forget the resistor!
In series, you only need one resistor.
In parallel, you need a separate resistor for each one, and you have the "resistor plus led" units in parallel across the voltage supply.

[Hal]

realize - in series, the total voltage drop = the sum of the voltage drops...so say each as a Vf of 2 volts, the total is 16 volts...in paralell the total voltage drop = the voltage drop of each...

so chose a resistor accordingly

[petemoore]

So I read between these lines and see that you could use LED's and Resistors to drop voltage...like for FF sag or bringing a power supply down to a usable range?

[Peter Snowberg]

So I read between these lines and see that you could use LED's and Resistors to drop voltage...like for FF sag or bringing a power supply down to a usable range?

Correct. Resistors will drop a voltage proportional to the amount of current the effect draws while a diode will drop a consistent voltage (between .5 & .6 volts for most silicon diodes).

Take care,
-Peter

[Mike Burgundy]

you can hook them up both in series and in parallel:
series: s stated current requirements stay the same and voltage goes up x times for x LEDs.
parallel: now *voltage* stays the same, but current goes up x times for x LEDs.

If you think of what each individual LED wants to see, and how that works out if you combine them, it's actually easy to understand. Just remember anything in parallel between A and B will share the same voltage drop between A and B (otherwise point A would have *two different potentials* which is impossible. Likewise in series, every component carries the same current between A and B.

If you can muster enough voltage, it's best to put them in series with a smaller resisitor for minimum loss (the supply *voltage* will be at a fixed value, so it's a good idea to keep current down for low consumption. In parallel you use a resistor to drop to 1-diode level (lotta loss) AND up the current: that draws a lot of power. )

[smoguzbenjamin]

Well I was thinking of putting it in an amp So power doesn't matter.
So if i used a 100 ohm resistor and after that wired 8 LEDs in parralel I could do it, if I read that all correctly.

Am I right?