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How big of a power supply will I need for RGB lights?
Last Updated: 02/11/2013
This article provides information that will assist you in selecting the correct power supply for your project using our RGB lights and/or DMX controllers. If you are not comfortable with this process, we recommend purchasing one of our pre-configured kits that includes the necessary coro element, power supplies, DMX controllers and lights - all designed to work perfectly together.
 
First you need to determine the design of your project and the number of RGB LED lights/modules/strips that it will require.  You will need to then determine the maximum current draw when ALL the colors (Red, Green, Blue) are on to form white for the RGB lights you have selected.  You can find these specs listed in our product descriptions or check with your RGB LED light vendor for additional details. 
 
An example would be 50ma (0.05 amps) with all LEDs on (white).  If you were planning to use 100 of these, you would be consuming 5 amps (0.05 x 100 = 5).  This is where things get a little more complicated as you need to also factor in the wire being used to carry the power.  In general, you should not hook more than 20 LED modules in series (end to end) due to the gauge of the wire.  Additionally, if you are using CAT5 cable, should not exceed it's MAXIMUM current carrying abilities which are generally .577 amps per conductor (1.1 amps per wire pair). 
 
So, if you had LED's at the end of a CAT5 cable that each required 50ma at maximum draw, the maximum number would be about 70 assuming you used 3 pairs of wires (one pair is generally used for the DMX data signal) - .577 * 6 = 3.5 amps.  3.5 / 0.05 = 70 LED modules.  Of course that is a maximum and it's generally recommended to only run at 80% of the rated capacity of the cable which would bring down the total number of LED modules to 56 modules on a cable powered by CAT5. 
 
Some other important things to be aware of when calculating power requirements:
  • As the length of the cable increases, so does the resistance.  Think of what happens when you hook together several garden hoses - the output of water starts to decrease with each new hose that is added to the previous one.  To accurately calculate these, you will need to know the specifics of your cable in resistance in ohms per foot of cable.  Due to the large number of variables in cables, connectors, LEDs, etc - we can not provide you a specific number or tell you how many per "X" feet can be used.
  • Add in the power consumption of any other devices on the line including the power draw of the controller itself.  Controllers are not 100% efficient and thus you can add 10 to 20% of power draw as the power passes through the controller, usually in loss by heat.  So, the power draw of 3, 50ma LED modules when run through a controller may be .18amps as opposed to just .15amps without the controller.  Of course the controller itself also requires a small amount of power to run it's processor.
  • We recommend verifying your calculations with actual measurements of the current consumption of the devices you are using.  For more information on how to do this, see our DC Controllers article.
Again, if you are unsure of how to properly configure and calculate power, purchase our pre-designed kits that include all the necessary RGB components that have been tested and confirmed to be 100% functional.

FAQs:
  • Q:  Can I measure the power consumption of my RGB lights using a Kill-O-Watt?
    • A:  Well, you can but we don't believe you will find it accurate for the following reasons:
      • It doesn't take into account the power loss from the AC to DC conversion, which is only about 80-85% efficient.
      • The Kill-O-Watt isn't an extremely accurate device - it is intended for "general" readings, not accurate ones and especially at lower wattages and can be off as much as 50% at these low levels.
  • Q:  Can I use one power supply to provide power to several/many controllers?
    • A:  Yes, the output of one power supply can be used to supply several controllers IF the current draw of all the lights and controllers is below the current output of the power supply.
 
Here is a video that shows how to measure power consumption for RGB lights using a multimeter:
 


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