I'm looking to buy a LED RGB controller that has the following specs:

  • 6A x 3 Channel
  • Output 18A Max

Given that a 12V 5050 SMD Led strips @ 60 leds/meter are 14.4W/1.2A per meter, this controller should be able to support 15 meters, assuming the driver has sufficient wattage.

And the driver should be rated accordingly + 10% ?

closed as off-topic by ThreePhaseEel, wallyk, Tester101 Nov 29 '16 at 13:26

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  • 2
    Sorry this is off topic for two reason, it's a product recommendation question, and it's electronics not home improvement. – Tyson Nov 26 '16 at 14:35
  • The maximum length depends on how much load you are putting on it, both by tapping power to drive closer lamps and in the resistance of the wiring. Your math ignores the latter, and may be more affected by the former than you expect. Simplest answer is either try it, or over-specify the power source a bit to leave room for the unexpected. – keshlam Nov 26 '16 at 18:01
  • I'm voting to close this question as off-topic because it belongs on electronics.stackexchange.com – wallyk Nov 27 '16 at 7:05
  • @Tyson Disagree, this is most likely a consumer application of kit lighting in a home. The distance is much too far for a vehicle, unless it's a train LOL! Given the season my guess is it's Christmas lights. – Harper Nov 28 '16 at 0:56
  • @wallyk also it is not a product recommendation because it's dealing with a class of standardized product, not any particular brand thereof. – Harper Nov 28 '16 at 1:04

Yes, your numbers sound correct to me. Another way of looking at the standard 60-per-metre 5050's is that they are 3-channel LEDs, with 400ma per metre per channel. (3528's are 1-channel LEDs, and the same applies; 400ma/metre assuming 60 LEDs per metre).

I would not use drivers (power supplies) with a 10% derate unless I was using top-tier suppliers (i.e. General Electric, Philips, etc.) Most people use cheap Chinese power supplies off eBay/Amazon, and for those I recommend a 100-200% derate, i.e. buy 2-3x the power supply you intend to use.

I don't know what your topology is going to be. Given the length and the season, my guess is this has something to do with Christmas lights on the interior or exterior of your house. These tend to have a lot of linear run distance. Let me talk about the challenges of carrying 12VDC a long distance.

First, there's the internal wires which run down the length of every LED strip. You can't use those. They are quite small, and don't have the current capacity to daisy chain more than one additional strip - that's 10 metres tops - and at that, you'll still have serious voltage drop which will mean the farthest LEDs will be very noticeably dimmer than the near ones.

There are two main ways to solve that problem.

One is to run your own external "feeder" wire, and since you're RGB, you'll need to run 4 wires. Then tie from your feeder to the strips everywhere you can - if possible, feed both ends. The wire will have to be fairly thick - run it through a voltage drop calculator and you'll see.

The second way is to avoid the voltage drop entirely by having several 120VAC/DC power supplies (drivers) distributed around the installation. Each driver feeds only the LED strips closest to it, so 12V doesn't have to go very far. How do you then control R/G/B mixing? You use a device called an amplifier (aka data repeater). It takes your controller's R/G/B output as a control signal at extremely low currents (easily handled by thermostat wire). It pulses each channel same as the controller was, and sends that to the lights.

A third option is to have a very fat 2-wire 12VDC feeder, and then several amplifiers distributed around as in the second option... so the 4-wire power only has to go a short distance.

Cost would decide which way to go: copper (wire) vs. silicon (power supplies/drivers/amplifiers).

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