LED strip segments Parallel vs Serial

automotiveledled striprgb

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

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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?)

Best Answer

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