LEDs do not care about the voltage. That 3 volt number is the
SMALLEST voltage that can pass through the LED. It will work fin at 12 or even 24 volts.
The AMPERAGE is the limiting factor and this is controlled by the resistor used. An LED is not a voltage consumer like an incandescent bulb, rather think of it like a rectifyer. (It *IS* a rectifyer, dony you know!) The resistor is put there to consume the voltage, or rather to limit the amperag.
Connect each LED with a resistor to your 12v lighting bus.
DO NOT wire them in series. Yes they Will work, but not for very long.
ROAR
The Route of the Broadway Lion The Largest Subway Layout in North Dakota.
Here there be cats. LIONS with CAMERAS
If you are not going to use a specific powerpack to supply 3Volt each LED gets it's very own resistor and all LED/resistor couples are run in parallel to each other.
Daisy chaining of LED is a bad practice and you are asking for various trouble.
Reinhard
Maybe this will help.
http://led.linear1.org/led.wiz
Brent
"All of the world's problems are the result of the difference between how we think and how the world works."
Let's make that link above clickable:
http://cs.trains.com/mrr/f/88/t/197622.aspx
Tom
https://tstage9.wixsite.com/nyc-modeling
Time...It marches on...without ever turning around to see if anyone is even keeping in step.
Here's an older post on the subject:
If it were me, I'd just buckle down and wire each LED and appropriate resistor separately; i.e., all in parallel.
Obviously you can't wire them all in series as the voltage requirement is additive and I doubt you want to use a 30v power supply.
You could put some in series to reduce your work, let's say three. They would need 9 volts for the LEDs and a resistor that would drop the extra 3 volts (if 12v supply). There are calculators out there. If wiring in series, the electrons need to go the same way through each LED so the electrons go in cathode #1, out anode #1, to cathode #2, out cathode #2, etc. (I probably have that backwards, EE was a long time ago). The resistor could be in either end or the middle as it just adds the needed marginal voltage drop.
Paul
Modeling HO with a transition era UP bent
I have 10 streetlights that are LEDs and came with resistors from the manufacturer. The LEDs are 20ma and the resistors are appropriate for 12v according to the mfger. The LEDs are 3v.
They are all going in a 4'x4' city area, so fairly close together. Should I wire them so that they all run together (called in series, right?) or connect each one separately to the bus wires (parallel?)
If I wire them in series, do I daisy chain one cathode and anode from one light to the next -- so cathode to cathode/anode to anode? Do I use one resistor? Where does it go in the chain? How many lights can I wire together this way?
If I do it in parallel, each light gets a resistor -- again, does it matter if the resistor is on the anode or cathode?
In either case, I would be using probably 12v-14v bus wires to tap into.
All help appreciated. I feel like I know just enough to screw it up!