led's in series...

[chrisatpsu]

if led's are in series, like a light string, do they all use the same amt of current that one uses, or do you add them all up?

[trekster]

Current stays the same in a series circuit.

Ron

[tbone321]

Which means that all of the LED's that you put into that circuit need to have the same current requirement.

[chrisatpsu]

so if one led is 20mA, then say a circuit of 1, 2, or 20 leds all in a series is still only 20mA? (i know the voltage adds up)

[tbone321]

The current will be whatever you set it at with the current limiting resistor depending on the voltage after the combined voltage drops.  The problem is that if your LED's are rated at different curents, you would need to set the resistor to keep the current at or below the rating of the lowest chip which could have the oter LED's being rather dim.

[Steve Gase]

think of it in terms of the watts of power being used.  tally up the watts and make sure that the PS can support it.  look at the wiring that delivers these watts -- calculate the amps flowing to those LEDs (watts/voltage=amps) and make sure that the wire size can handle those amps.