Relationship between voltage/current & LED strips?

Question

I recently bought a WS2812 LED strip (5 meters, 300 LEDs)

When the LEDs are driven at full brightness and each color lit, they draw 60mA each--or 18 amps for all 300!

This led to a problem, which led to a question.

A friend suggested that I not attempt to power the whole strip at once, because even if I could, 18 amps would probably burn it up. So, the other option is to splice in power leads every so often, which is recommended by the manufacturer.

I took a look at my power supply and realized that while it can supply between 0-24vdc, it can only supply 5 amps.

Is there no difference between 12v at 5 amps, and 5v at 5 amps other than power? I understand that Power = amps * volts, so 12v at 5 amps is 60 watts, and 5v at 5 amps is only 25 watts. My question is this: shouldn't the limiting factor be the wattage, not the current? If my power supply can supply 24v at 5 amps (it can), this is 120 watts. In order to supply 120 watts at 5 volts, I would be hitting 24 amps.

Answer 1

You are partially correct. All three: power, current, and voltage are limiting factors for your power supply. If your power supply is labeled 0-24VDC @ 5A max, then it means it can handle these max ratings:

• Max Voltage: 24V
• Max Current: 5A
• Max Power: 120W

So you say your LED's draw 18A total. This is only half of the equation. You also need to know what voltage the strip needs to be supplied. If the voltage that the strip requires is less than 1/18 of 120 (6.67V), then congrats, your power supply can handle your LED strip. If the required strip voltage is > 6.67V, then your total power draw will be > 120W which is no good. However, you can't just willy nilly plug the LED strip into the power supply because remember, your power supply can only handle 5A. The easiest way to overcome this problem is through the use of a power transformer to turn 24V into your required voltage.

^{simulate this circuit – Schematic created using CircuitLab}