Extracting led from led strip 5630

Hi there,
I have a led tape strip 5630-60D (12v) which one can cut every 3 leds.
Nw the thing is that I need only one led (actually 3 separated which I plan to drive later with a nano and a l298n module)....
The question is which tension and resistance do I need for a single led?
I've made some measurements on a 3led segment trying to understand.... Here below my primitive results:
+o------1------|>|---2---///----3----|>|----4----|>|----o-
1: 11.83v
2: 8.67v
R between 2&3: 39 Ohm
3: 6.5v
4: 3.31v
The current consumed: 55mA

My humble conclusions... The voltage drop of the led is 3.2v and the I of one led is 55mA
Now I guess if I plan to supply 12v-3.2v/55mA = 160Ohm.... Chossing a 180Ohm will give me a 49mA dissipating a lot of power on the resitor... so probably it would be smarter to drive it under 5v with 33Ohm --> 54.5mA
So the real questions are:

  1. are my calculations right?
  2. could I drive this led directly from the nano at 5v at 55mA or do I need to reduce the current (to the 40mA from nano spec) if I want to drive directly?

Thank you in advance!

That's too much current. Get yourself a small transistor, drive the transistor base thru a 200 ohm resistor, and use the transistor to sink current thru the LED to Gnd. The arduino can't sink current from a 12V source, while an external transistor can.

Thank you CrossRoads. What about my calculations? If I remove a single led should I use a 180Ohm @ 12v / 33Ohm @ 5v?

They are deisgned to be grouped in 3's....no?

(hence the 12 volt requirements on those type of strips?)

If you are trying to remove and use only 1 led... you dont need 12 volts anymore.. as they are not grouped together to take the 12v any longer.

post a link to the exact led strip you are trying to use/hack a part.

55mA is to much for an Arduino pin. Even 40mA is absolute max so recommended is max 20mA to 30mA per pin. And it also has a total max of 200mA. So get yourself a transistor to drive them :slight_smile:

And yeah, voltage drop of 3,2V is about right. So indeed around 33Ohm. Or make it easy and just grab the part with the 39Ohm already on it :wink: Will give you 46mA @ exactly 5V but you will barely notice the difference.