Power Supplies

Intro

When you're working with Pixels, Dumb RGB or any type of LEDs, they need to 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. There are four main properties to a power supply:

• Waterproofing
  • Waterproof Supplies
  • Non waterproof Supplies
• Input Voltage
  • 120 VAC (nominal)
  • 240VAC (nominal)
    • Multivoltage
• Output Voltage (common voltages used by pixels include)
  • 5VDC
  • 12VDC
• Output Current
  • Can be any number, based on your usage.

Since power supplies can put out a lot of power it is important to use a fuse on the output of the power supply. It is also critical to use the proper sized wire along with the power supply. The wrong size wire could be a safety hazard or could cause your pixels to not function properly due to excessive voltage drop in the wire.

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

You must buy a power supply with the correct voltage to match your pixels and controller. Using the wrong voltage can destroy your pixels and controller by hooking them up even once to the wrong voltage!!

Once you decide on which of the Different Styles of Pixels you want to use, you also need to Choose a Pixel Voltage: 5V vs 12V. The choice comes down to the actual setup you are planning and their are advantages and disadvantages to each.

With 5v the voltage drop due to the wiring will be noticeable if you're 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 a lot 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 now available in 5VDC and 12VDC. 12VDC power supplies are typically more expensive per amp of current. Also many 12vdc strings waste a lot of power as heat and not light, so they are not as efficient as 5VDC strings.

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.

Power Supply Current

You need to choose your power supply based on the voltage required by your pixels and the current that is consumed by the pixels. You can always chose a power supply with a higher current rating then your planned usage.

The current rating of a power supply is a measure of how much current is available at the output voltage of the power supply. For example:

• A 300W Power supply that is designed for 5VDC output can supply up to 60A of current at 5VDC. The input voltage for many of these supplies is commonly 115VAC and would draw about 2.6A of current from the wall outlet. You do not have to use all 60A of DC power, you can use less.

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 60A, you do not want to put more than a (60*0.8)= 48A worth of load on that power supply.

Since typical LEDs draw 20ma (0.02A) each, and a Pixel or Dumb RGB 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 total current you will need, you must 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

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 Supplies from a PC

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. Since these power supplies were designed to work inside of a PC, you need to come up with an enclosure to mount them in. There are many types of Enclosures that you can mount your power supply inside of including the [CG-1500] which can provide a large enough enclosure that you can mount both a power supply and a controller inside of. There are numerous plans available on the internet showing you how to convert ATX PC Power Supplies. For more information see:

• Murray State
• Mad Science Notebook
• Instructables
• Wikihow
• Sparkfun Breakout Board

ATX Power Connector Pinout:

Wall Warts

Wall warts have limitations and are difficult to try to run pixels off of. First off most are too small to supply enough amperage. Also they do not supply very clean or stable power to the pixels. Your best bet is to stay way from them.

DC - DC Converters

If you already have a DC Power supply at a different voltage from what you need, you can use a DC - DC Voltage Converter to either raise (Boost Converter) or lower (Buck Converter) the voltage to a different voltage. Generally these devices are limited to a few Amps (<3-5A) of current. You can purchase these devices on Ebay.com, DX.com, Allliexpress.com or other electronic parts vendors.

Buck Converter

Buck Converters are used to drop a higher voltage to a lower voltage. A common use would be to drop the output of a 12VDC power supply down to 5VDC. A Buck Converter is highly efficient (>95%) and generally does not need a heat sink which a Linear Regulator like a LM7805 would require. Examples devices are here, here or here.

Boost Converter

Boost Converters are used to raise a lower voltage to a higher voltage. A common use would be to raise the output from a 5VDC power supply to 12VDC. Boost Converters are also highly efficient (>95%). Because they convert power from one voltage to another, the current consumed at the lower voltage is higher then the current supplied at the higher voltage. Ohm's Law defines the relationship between Power = Voltage * I (current) Example devices are here or here.

Power Supply Connections

Power supplies generally have screw terminals or wires from the power supply that you can connect to your controllers. Your power supply may vary, but common markings include:

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- (COM)	Negative voltage output to Controllers

Fuses

DC Power Supplies are capable of putting out hundreds of watts of power and causing serious damage, always use properly sized fuse for safety! Due to the very high current that many power supplies are capable of putting out (>60A) it is a good design concept 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. The fuse is a safety factor to prevent the full power from the power supply from discharging thru a short circuit and potentially causing a fire. The correct size fuse rating should be selected based on the expected power usage of the units hooked up to the power supply. It is common to use 12-14ga wire to connect power supplies with high count pixel controllers like the E682. Mouser.com carries several inline fuseholder that take automotive style fuses such as part number 441-R347A-GR or 576-FHAC0002ZXJ that have 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.

Automotive style ATC and ATO fuses are available with ratings of 1, 2, 3, 4, 5, 7 1/2, 10, 15, 20, 25, 30, 35 and 40A. Choose the fuse based on the maximum current that you expect from your Pixels thru that section of wiring.

Many Pixel Controllers like the E682, E6804 and the Renard PX1 have separate output fuses connected to each output connector already on the controller. A common rating for those fuses are 5A. They are generally Mini automotive fuses. Mini fuses are available with ratings of 2, 3, 4, 5, 7.5, 10, 15, 20, 25, 30A.

Wire Sizing in Pixel Systems

In high current and low voltage systems like Pixels and Dumb RGB it is critical to use the SHORTEST length of THICK (low gauge) wire to minimize voltage drop. Wire like Cat5 is just to thin for most uses.

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 as well as pixel spacing and wire used in the strings themselves..

The voltage drop occurs in three major areas:

• Power wires from the Power Supply to the Pixel Controller
• Power wires from the Pixel Controller to the Pixel string/strip
• Power wires in the Pixel string/strip

A simple example is how you choose the right size wire between the Pixel Controller and the Pixel string/strip. You can 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%! That may work for short strings of pixels.
4. What is the voltage drop for the same string of 5VDC pixels that have a 5ft length of 18 gauge wire between the beginning of the string and the controller?
   The total resistance of the wire would be (5 foot)*(6.39x10^-3) = 0.0320 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 0.0640 ohms.
   By Ohm's Law we know that V=IR, so the voltage drop is V = (3A) * (0.0640 ohms) = 0.1917 V So instead of your pixels getting 5V they are only getting 5 - 0.1917 = 4.8083V a drop of only 4%! Short thick wires are the answer!

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.

A classic symptom of the voltage being too low at the end of a pixel string is the pixels may look Pink instead of White when turned on fully White. If the color of the first pixel in a string is different from the last pixel in the string, it is likely due to the voltage drop in the string and the wires supplying it. 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.

If all you have is higher gauge wire, it is possible to double or triple up the wires (use 2 or 3 parallel wires for the V+ and Ground) to help reduce the effective wire resistance.

Common wire used for Pixels include larger gauge (10-18 AWG) Speaker wire, Security Alarm Wire, Low voltage landscaping wire, Sprinkler wire, SPT wire and various wire types available from the pixel vendors. You must pay attention to the wire size (thicker is better) and length (shorter is better) to ensure that the voltage drop over the wire is not excessive. Do not use thin wire (20-26 AWG) like Cat5 or Cat6 wire. The voltage drop over thin wire is often too high to allow the pixels to operate properly. Thin wire also is a safety hazard and can heat if too high a current is used on it.

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

Related Links

Different Styles of Pixels
Controllers
Dumb RGB or Intelligent Pixels??
Things You Will Need To Get Started With Pixels
Pixel Wiring Colors
Pixel Connectors
Choosing a Pixel Voltage: 5V vs 12V
Power Injection
Waterproofing Pixels
Null Pixels