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I have 5050 RGB LED Strip and an RGB controller (Something like this http://www.amazon.com/SUPERNIGHT%C2%AE-Waterproof-Flexible-300leds-Changing/dp/B00ASHQQKI/ref=pd_sim_MI_3?ie=UTF8&refRID=0KQRVAR859JNNWFDFDHG but bought from the Indian market at a much lesser price.)

I want to place this entire setup in my car and connect it to the Dome light switch. The connections are all easy as the dome light is already providing 12V. the strip has 300 LEDs all connected in parallel. And has 100 segments (3 LEDs each) where it can be cut without disturbing the strip

enter image description here

Now for convenience I have cut the strip into multiple sub strips (containing either 7 segments or 10 segments. to be placed at different places through out my car. The problem is with connecting them. The LEDs are already in parallel within each sub strip. Now I am worried that connecting each substrip in parallel to the RGB controller would require even higher current. The RGB controller is rated at 1.5A output. Should this parallel setup of substrips be fine? Or should I figure out a way to connect them serially to the RGB controller? so that it looks like an extended strip with wires connecting the sub strip.

Edit: One more thing, The controller comes with a 12V adaptor rated at 2A output. I am planning to connect the RGB controller directly with the dome light, Should I install some sort of protection there (to limit the current at 2A maybe?)

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  • \$\begingroup\$ The current consumption will be the same either way round, because as you say the LEDs are in parallel in each strip. However, the one you've linked has a 5A consumption so you'll need a bigger controller. \$\endgroup\$ – pjc50 Oct 20 '14 at 14:51
  • \$\begingroup\$ Parallel circuits in parallel == parallel?. I actually didn't do the math, should I be concerned? Or I am going good? \$\endgroup\$ – whizzzkid Oct 20 '14 at 14:54
  • \$\begingroup\$ I think you'll find they're not 3 LEDs in parallel, but 3 LEDs in series. Multiple chains of 3 series LEDs in parallel, with each "join" being where they are paralleled. \$\endgroup\$ – Majenko Oct 20 '14 at 14:59
  • \$\begingroup\$ no but, in this case the strip works fine even if one led goes bad. That means all would be in parallel. So Now what I have is 1 substrip = 10 segments (30 Leds in parallel) now I want these substrips to be further parallel to each other. \$\endgroup\$ – whizzzkid Oct 20 '14 at 15:01
  • \$\begingroup\$ Parallel is what they were before you cut them. By placing them back in parallel you're not changing anything. \$\endgroup\$ – Majenko Oct 20 '14 at 15:06
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Dumb RGB LED strips like you have are simple. Each segment consists of 3 channels. Each channel has 3 diodes and 1 resistor in series. Each segment is in parallel with each other. Cutting and extending the sections with wire does not change that. You will not experience an increase in current because of it (in fact, extending with wire will actually cause a decrease in current, due to the non-zero resistance of the wire. For your short runs, this is negligable).

That said, adding 100 segments, each with 3 ~20mA channels (so 20mA x 3 x 100 = 6 Amps!) To the dome circuit of your car will A, cause the fuse to blow, probably, and B, cause a fire as wiring for the dome light is not sized for multiple amps. A relay in line with the dome switched circuit, to a new fused circuit (or the cig circuit, that's normally fused for 10 Amps) is the safe approach.

Update: a 1.5 Amp controller will not work well with a full 300 led/5 meter length of rgb led strips... At most you can power 25 segments! Thats 500mA per channel/color

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  • \$\begingroup\$ Find the wiring schematic for your car. Its a godsend in doing these projects right. \$\endgroup\$ – Passerby Oct 20 '14 at 16:27

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