Powering LED Strip with the right supply

Question

I am currently working to power a very large project. I am in the US and am planning to run some large amounts of 5M (16.4') 12V 5050 RGBWW Supernight 300 LED/strip (EBT459). I calculated the length I need to run as 72.5'. My calculations are as such...

The strip I am using uses 3.2 watts per foot, so calculating in with 72.5' gives me a total of 232 watts. Adding in the Rule of 80% it comes out to 290 watts. After calculating amperage, I am at 24.16 amps, so 1- 12v, 30A, 360W power supply.

However, I am running 8 strips, 4 per level, which will require signal amplifiers, set in between each run of 2 strips (10 meters) to combat dimness.

I decided to up the power supplies to be 2- 12V, 60A, 720W power supplies, one to run each length of 4 strips. These will be connected into a TC420 LED timer box then run to the LED strip to control color effects.

My question is, can I run the LED signal amplifier, from the SAME power supply as the strip will be connected to? Meaning, run the leads for the amplifier back to the same power supply that will be connected to the LED controller and have 1 power supply be able to power the entire 72.5' of strip, or will I have to break it down and run multiple power supplies, meaning 1 power supply to run each 2 strip section of LED?

Answer 1

The main concern when running long lengths of LED strip lighting is voltage drop. Or, put another way, the resistance of the wire (the copper traces on the strip) over distance will add up, resulting in power losses.

LED strips are usually made using FPC (flexible printed circuit) material, with varying thickness and purity of copper. Using a PCB trace width calculator, you can determine what voltage drop to expect with various characteristics.

• 34.8µm (1 oz) copper thickness
• 5 mm trace width
• 5 meter distance
• 5 A current
• 25°C ambient temperature

For the above properties, the voltage drop is about 2.5V, with 12W power loss. I am guessing on the copper thickness and trace width. It's not uncommon for such strips to use thinner copper (the price should reflect this).

This calculation is all well and good, but actually measure it to get a better idea of what to expect. Connect power to one end of a strip, run all LEDs at full white, and measure the voltage on the opposite end.

With a 12V strip, you probably won't notice much of a problem with a drop of <2V. As the voltage drop increases, a gradient in the color of the LEDs will become more noticeable. LEDs closest to the power supply will be brighter than those farther away. The most dramatic effect is with full white, where maximum power is drawn.

If your installation allows you to run physical wires to the endpoints of the LED strips, do that. Running 16 AWG wire from the power supply to the opposite end of the LED strip (5 meters) will only have a voltage drop of about 0.7V with the same 5A current. Think of these wires as distribution lines for your lighting installation. In other words, don't rely on the LED strips alone to distribute power evenly.

To answer your main question, yes you can have the power supply providing power to both the strip and the repeater, by using appropriate wire to connect them when you take into account the voltage drop. If you have a power supply sized to operate the entire installation, you could potentially home-run all wiring to it (again, sizing the wire correctly). You might find that multiple power supplies at convenient locations is cheaper/easier. Those questions depend on the physical characteristics of your installation location and budget.