Power Supplies

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Intro

When your working with pixels or any type of led, they will be run on DC voltage. To do that you will need to run some sort of power supply. There are many types you can use. A power supply converts high voltage AC power from your wall outlet (commonly 115VAC in North America) to a lower voltage DC current to drive your pixels. Common voltages used by pixels are:

  • 5VDC
  • 12VDC

You need to choose your power supply based on the voltage required by your pixels and the current that is consumed by the pixels. A common practice is to only use a power supply at 80% of its rated capacity. For example: if a power supply is rated for up to 30A, you do not want to put more than a (30*0.8)= 24A worth of load on that power supply.

Since typical LEDs draw 20ma (0.02A) each, and a pixel has three LEDs inside (R,G,B), then a general rule of thumb is that each pixel will draw 60ma (0.06A) of current. To calculate the current you need you need to count the number of pixels you plan to power from that power supply. For example:

  • If you are using 50 pixels, you will need (50*0.06A)= 3A of current.
  • If you are using 800 pixels, you will need (800*0.06A)= 48A of current!! (and some big wire too)

Some 12VDC pixels draw less current, check with you vendor to confirm their current draw. Voltage, Current and Power are electrical properties of electronic circuits that are related to each other by Ohm's Law. Power = Voltage * Current

Disclaimers

The standard disclaimers pertaining to the information contained on this wiki page are listed here.
THIS WIKI PAGE IS NOT COMPLETE YET AND HAS NOT BEEN CHECKED FOR ERRORS.

Power Supply Voltages

With 5v the voltage drop will be noticeable if your trying to push the voltage for a long run. Most likely you will need to inject the power again or feed from the center of the pixel string. For every 50 pixels, you should re-inject the power. So a good example, if you have a 100ct pixels string you can connect the signal wires end to end, but you will either have to put the power at the center of the string to feed each side. Or you will have to put a power source on either end. A 50ct pixel string will pull around 3amp (50x.06=3amp). So really finding smaller power supplies is a good thing to have if you have your pixels spread around the yard. If you have like a pixel megatree then you can do a large power supply to feed the whole tree. So bigger is not always better esp if your not power alot of pixels close by.

12 volt is a bit different. You can push 12v further than 5v. So that does have its advantages and disadvantages. Most pixels strings are only 5v. There are some that are starting to 12v but it may be a bit before more start to come out. So 12v is alot nicer but not as many options.

You can add a low cost voltmeter in your enclosure to monitor the voltage output from your power supply. They are available here and here or here.

Waterproof Power Supplies

Waterproof power supplies are really nice in the sense that you do not have to really worry about moisture as much as a non waterproofed power supply. Before placing a "waterproof" power supply in a weather exposed area, check it's IP rating to determine what level of protection is required. You should still put it in some sort of shelter just to be safe. These are a little more pricey than a standard switch mode power supply but alot less headache. They come in a variety of sizes so you will have to choose what will work best for you.

It is common to use waterproof power supplies with waterproof connections.

Examples of Non Waterproof Power Supplies available from different vendors

PLEASE CONFIRM ALL DETAILS WITH VENDOR BEFORE ORDERING!! ALL OF THIS DATA IS SUBJECT TO CONSTANT CHANGE AND MAY BE WRONG!!!
Pricing is in US $. Pricing is as of 6-24-13.
PRICING DOES NOT INCLUDE SHIPPING, TAXES OR IMPORT DUTIES!
Shipping from overseas can be expensive, check with your vendor.

Vendor Type Input Voltage Output Voltage Output Current Link Image Price Price per Amp Size (HxWxL) Note
5VDC
DIYLEDEXPRESS 60W Waterproof Switching Mode 90-130VAC 5VDC 12A link $20.75 $1.73 45mm x 67mm x 175mm Cable;VDE BVVB,200MM Long
Ray Wu 60W Waterproof Switching Mode 90-250 VAC 5VDC 12A link $12.63 $1.05 45mm x 67mm x 175mm IP68
12VDC
Holiday Coro 45W Waterproof Switching Mode 100-130 VAC 12VDC 3.75A link $12.39 $3.30 1"x1.2"x9.7" IP67
Ray Wu 60W Waterproof Switching Mode 85 - 264 VAC 12VDC 5A link $12.63 $2.53 45mm x 67mm x 175mm IP68
24VDC
DIYLEDEXPRESS 100W Waterproof Switching Mode 110 VAC 24VDC 4A link $28.75 $7.19 45mm x 67mm x 210mm IP68

Non Waterproof Power Supplies

Since they are not rated as waterproof, you must use these supply in some form of enclosure if you want to use these outside to power your DC LEDs. There are many types of Enclosures that you can mount your power supply inside of including the [CG-1500] provide a large enclosure that you can mount both a power supply and a controller inside of. Most of the supplies have a small adjustment potentiometer that you can use to adjust the voltage output slightly.


Examples of Non Waterproof Power Supplies available from different vendors

PLEASE CONFIRM ALL DETAILS WITH VENDOR BEFORE ORDERING!! ALL OF THIS DATA IS SUBJECT TO CONSTANT CHANGE AND MAY BE WRONG!!!
Pricing is in US $. Pricing is as of 6-24-13.
PRICING DOES NOT INCLUDE SHIPPING, TAXES OR IMPORT DUTIES!
Shipping from overseas can be expensive, check with your vendor.

Vendor Type Input Voltage Output Voltage Output Current Link Image Price Price per Amp Size (HxWxL) Note
5VDC
DIYLEDEXPRESS 300W Switching Mode 100V~120 VAC 5VDC 60A link $27.75 $0.46 49mm x 114mm x 226mm Fan Cooled
Holiday Coro 350W Switching Mode 100-130 VAC 5VDC 60A link $32.95 $0.55 2"x4.5"x8.5" Fan Cooled
Ray Wu 350W Switching Mode 85 - 264 VAC 5VDC 60A link $20.00 $0.33 50mmx115mmx215mm Fan Cooled
12VDC
DIYLEDEXPRESS 360W Switching Mode 100V~120 VAC 12VDC 30A link $27.75 $0.93 50mm x 112mm x 214mm Fan Cooled
Holiday Coro 350W Switching Mode 100-130 VAC 12VDC 29A link $29.95 $1.03 2"x4.5"x8.5" Fan Cooled
Ray Wu 350W Switching Mode 85 - 264 VAC 12VDC 29A link $20.00 $0.69 50mm x 115mm x 215mm Fan Cooled
24VDC
DIYLEDEXPRESS 200W Switching Mode 100V~120 VAC 24VDC 8A link $28.00 $3.50 50mm x 112mm x 214mm Fan Cooled

Converting ATX Power Supply

One common low cost way to generate +5VDC and +12VDC is to convert an old used PC power supply that you have salvaged from an unused PC. There are numerous plans available on the internet showing you how to convert them.For more information see:

Wall Warts

Wall warts are not the greatest to try to run pixels off of. First off most are too small to supply enough amperage. Also they do not supply very clean power to the pixels. Your best bet is to stay way from these.

Power Supply Connections

Power supplies generally have screw terminals or wires from the power supply that you can connect to your controllers.

Typical Power Supply Connections
Label
Connection
L - Line Connects to the Hot side of 115VAC power cord(Black wire)
N - Neutral Connects to the Neutral side of 115VAC power cord (White wire)
Gnd - Ground - Connects to the Ground wire of 115VAC power cord (Green wire)
V+ Positive voltage output to Controllers
V- Negative voltage output to Controllers

Fuses

Due to the very high current that many power supplies are capable of putting out (>60A) it is a good idea to use a heavy gauge wire inline fuse holder between the power supply and the controller hookup. The large gauge wire will minimize any voltage drop that may occur in the wire due to high current. It is common to use 12-14ga wire to connect power supplies with pixel controllers. Mouser.com carries several inline fuseholder that take automotive style fuses such as part number 441-R347A-GR that has 12 ga wire and can use up to 30A ATC style fuse, or part number 441-R347B-GR that has 14ga wire and can use up to a 20A ATC style fuse.

Wire Sizing in Pixel Systems

It is desirable to use the largest wire diameter (smaller wire gauge AWG) that you can when connecting your pixels to your controller. The higher wire gauge results in a higher voltage drop and can cause your pixels to have poor colors or to not function at all. The voltage drop is caused by the resistance in the wire and is calculated by Ohm's Law. This is a good thread that discusses voltage drop. This is a Voltage Drop Calculator useful for calculating the effects of different wire sizes and lengths on pixel strings.


You can also use the data from the table below to estimate your voltage drop based on the current and wire gauge you will be using. For example:

  1. What is the voltage drop for a string of 5VDC pixels that draw 3A that have a 10ft length of Cat 5 Wire (24 gauge) between the beginning of the string and the controller?
    The total resistance of the wire would be (10 foot)*(25.67x10-3) = 0.2567 ohms, but since the current goes down one wire and returns on the second wire, you need to double the resistance, so the total loop resistance is 0.5134 ohms.
    By Ohm's Law we know that V=IR, so the voltage drop is V = (3A) * (0.5134 ohms) = 1.5402 V So instead of your pixels getting 5V they are only getting 5 - 1.5402 = 3.4598V a drop of 31%! Your pixels would not work ...
  2. What is the voltage drop for the same string of pixels that have a 10ft length of 22 gauge wire between the beginning of the string and the controller?
    The total resistance of the wire would be (10 foot)*(16.14x10-3) = 0.1614 ohms, but since the current goes down one wire and returns on the second wire, you need to double the resistance, so the total loop resistance is 0.3228 ohms.
    By Ohm's Law we know that V=IR, so the voltage drop is V = (3A) * (0.3228 ohms) = 0.9684 V So instead of your pixels getting 5V they are only getting 5 - 0.9684 = 4.0316V a drop of 20%! Getting better, but still not good.
  3. What is the voltage drop for the same string of 5VDC pixels that have a 10ft length of 18 gauge wire between the beginning of the string and the controller?
    The total resistance of the wire would be (10 foot)*(6.39x10-3) = 0.0639 ohms, but since the current goes down one wire and returns on the second wire, you need to double the resistance, so the total loop resistance is 0.1278 ohms.
    By Ohm's Law we know that V=IR, so the voltage drop is V = (3A) * (0.1278 ohms) = 0.3834 V So instead of your pixels getting 5V they are only getting 5 - 0.3834 = 4.6166V a drop of only 8%!

When you factor in the voltage drop due to the wire in the pixel strings themselves ( a harder calculation, use the calculator mentioned above) the final pixels at the end of the string may not have enough voltage to light or function properly. This is why folks often use Power Injection at the end of the pixel strings to boost the voltage to the pixels at the very end of the string. You should always use the largest diameter wire you have available (smaller gauge) to connect your pixels with the controller and to use for power injection.



The following data is from http://www.powerstream.com/Wire_Size.htm Load Carrying Capacities (see table below)

"The following chart is a guideline of ampacity or copper wire current carrying capacity following the Handbook of Electronic Tables and Formulas for American Wire Gauge. As you might guess, the rated ampacities are just a rule of thumb. In careful engineering the voltage drop, insulation temperature limit, thickness, thermal conductivity, and air convection and temperature should all be taken into account. The Maximum Amps for Power Transmission uses the 700 circular mils per amp rule, which is very very conservative. The Maximum Amps for Chassis Wiring is also a conservative rating, but is meant for wiring in air, and not in a bundle. For short lengths of wire, such as is used in battery packs you should trade off the resistance and load with size, weight, and flexibility. NOTE: For installations that need to conform to the National Electrical Code, you must use their guidelines. Contact your local electrician to find out what is legal! "

Number of Channels (*)
Properties of Copper Conductors
AWG Gauge Conductor
Diameter Inches 		Conductor
Diameter mm 		Ohms
per foot 		Ohms
per meter 		Maximum Amps
for Chassis Wiring 		Maximum Amps
for Transmission
8 0.1285 3.2639 0.63x10-3 2.06x10-3 73 24
10 0.1019 2.58826 1.00x10-3 3.28x10-3 55 15
12 0.0808 2.05232 1.59x10-3 5.21x10-3 41 9.3
14 0.0641 1.62814 2.53x10-3 8.28x10-3 32 5.9
16 0.0508 1.29032 4.02x10-3 13.17x10-3 22 3.7
18 0.0403 1.02362 6.39x10-3 20.94x10-3 16 2.3
20 0.032 0.8128 10.15x10-3 33.29x10-3 11 1.5
22 0.0254 0.64516 16.14x10-3 52.94x10-3 7 0.92
24 0.0201 0.51054 25.67x10-3 84.20x10-3 3.5 0.577
26 0.0159 0.40386 40.81x10-3 133.86x10-3 2.2 0.361
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