Choosing a Pixel Voltage: 5V vs 12V

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General

There are many Different Styles of Pixels that are available with different design features like shape, integrated circuit and voltage available. Choosing the right pixel depends on your specific use plans and one of the most common questions is which voltage pixel should you buy. Choosing between the two most common voltages, 5vdc and 12vdc depends on how you plan to control and how you layout your pixel setup. There are a few general rules:

  • Long strings (>50 pixels) are less likely to need power injection if they are driven by 12vdc.
  • Long distances from the controller to the first pixel is easier with 12vdc.
  • 12vdc power supplies are more expensive per Amp then 5vdc power supplies.
  • Some low cost and homemade controllers only work with 5vdc.
  • Some 12vdc pixels use less current then traditional 5vdc pixels.
  • Voltage drop and power injection are important issues for both voltages.

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How RGB LEDs work


Common Anode RGB LED

Current Limiting Resistors

Ohm's Law

  1. What resistor would you use with a 5VDC power supply and a Blue 8mm LED with a VF of 3.0V?
    First you need to calculate the voltage that the resistor needs to drop. That is equal to
    VDrop=VPowerSupply - VF=5-3=2V
    The table below recommends a current I of 20 ma for a 8mm LED. The formula for resistance gives us:
    R=V/I=2/0.02=100Ω Generally you choose a resistor for that value or the next higher standard resistor value.
    To calculate the wattage resistor needed you use the formula for Power:
    P=VI=(2)(0.02)= 0.04W. You would use the next standard size up resistor, 1/8 W.
Number of Channels (*)
Typical 8mm RGB LED Properties
Color Forward Voltage VF @ 20ma
Minimum Typical Maximum
Red 1.8V 2.0V 2.2V
Green 3.0V 3.2V 3.4V
Blue 3.0V 3.1V 3.4V

Different Voltage Configurations

5V Power and 1 RGB LED

12V Power and 3 RGB LEDs

12V Power and 1 RGB LED


Related Links

Different Styles of Pixels
Controllers
Dumb RGB or Intelligent Pixels??
Things You Will Need To Get Started With Pixels
Pixel Wiring Colors
Power Supplies

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