Not sure if this is the appropriate place, or something like DIY. I have purchased 6 of these light bars from Amazon https://www.amazon.com/gp/product/B074NX7H1K/

The power supply is 6A and each bar takes .3A (4W / 12V). So the power supply should be sufficient.

I know that wiring in parallel each light will get 12V and reduce the current.

The light bar itself seems to be a set of 24 LED diodes with a resistor (hard to read the ohms through the frosted plastic) every 2-3 lights.

My plan is to wire nut them all together directly to the spliced end of the powered source, with a separate run for each light. Alternatively, I might create 3 'feeds' and then wire them in parallel in a set of 2. As far as I understand that is the same thing.

Are there any problems going this route? Will this suffer from thermal runaway or anything? If it does, how can I calculate what size resistor I would need before each light bar? If I don't put in a resistor, realistically how much would this reduce the life of the lights?

Please note that I am a layman and can't really understand electrical diagrams, but I will try my best.

migrated from electronics.stackexchange.com Dec 5 '17 at 18:00


  • By the bits they give you it looks like they should be hooked up in series, but what does the manual say? – Trevor_G Dec 5 '17 at 17:59
  • 1: That listing shows 3 bars. Did you buy 6 sets of 3 (for 18 in total) or 2 sets of 3? 2: The controller is rated for 6A, The Power Supply is only rated for 1.5A (look further down the page to the Specifications paragraph), so either way you're probably out of luck with using just one supply unless you buy a new one. – brhans Dec 5 '17 at 18:07
  • @brhans Sorry, I bought 2 orders, so 6 bars in total. Sorry I forgot to mention that I did replace the power supply. – esac Dec 5 '17 at 18:31
  • Then you're probably all set to go - just follow Dave's answer below. – brhans Dec 5 '17 at 18:34

Three LEDs per resistor is a common arrangement for fixtures designed to be connected directly to 12V.

No external resistor is required.

Your plan to connect them all in parallel is correct. Just make sure that the total current (0.3A per fixture × 6 fixtures = 1.8A) doesn't exceed the capacity of the power supply.

The lamps can be "daisy chained" with one cable running from the power supply to the first lamp, then a cable from there to the next lamp, and so on. However, electrically, this is still a parallel connection across the power supply, not a series connection. Each lamp is still getting the full 12V.


I have little to add to Dave Tweed's excellent answer.

You wire each strip electrically parallel.

If the features of the light allow, you can wire them as a daisy chain, connecting one strip into another strip into another strip. That is not strictly "series", but it is often called that incorrectly. I call it daisy-chain, like you might chain extension cords.

This probably relies on the internal "wires" (circuit traces) inside the LED strip proper, and if they are using commodity strips, those are good for 2-3 amps tops.

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