In Christmas lights, both AC and DC currents are used depending on what kind of lights are being used. Some lights use AC currents, and some lights use DC currents. In DC currents, electrons flow through one end of the bulb, and out the other end. When turned on, a DC electric current has a steady flow of electricity.
As a starting point, most Christmas light sets are wired for standard household AC, or alternating current. This means that they cannot be powered with DC, or direct current, without some modification. However, there are some sets of LED Christmas lights that are battery operated and are already wired for DC.
LED strips, unfortunately, are not as simple as traditional incandescent light bulbs when it comes to installation and set up. Because they run on low voltage DC, they require a power supply device that converts 120V/240V AC (depending on your location) into the voltage signal that LED strips can use.
Holiday lights are a great way to learn about the flow of electric current. In a simple circuit, including one in an incandescent light bulb, electricity travels through a closed circuit, passing over a filament, causing it to glow brightly.
Some older parallel sets had 15 bulbs, as do some of the newer globe sets manufactured today. Both of these bulbs are designed to run on 120 volts AC and the light sets that use them are wired in parallel.
Interestingly, older landscape lighting systems may have been 12 volts of AC power. Most of us think of AC power as the type that comes out of the wall. DC power is usually thought of as battery power. Now, with LEDs being the common lightbulbs, most landscape lighting installs utilize 12 volt DC power.
Most string lights require 2.5-volt or 3.5-volt bulbs.
Each light has its own wire to the source. The source of electricity for Christmas lights is a basic AC outlet. Just plug it into a socket and you get your power from 110–140VAC or 210–240VAC source (depending on the country's AC specifications).
Christmas lights are wired as a “series” of lights along a single electrical path. That means that the first bulb must past electricity to the next, sequentially, from first to last in the series for ANY of them to light up.
The blue line connects all the lights together in series and supplies power to the light bulbs. The yellow and red wires are both connected to the blue line on either side of the light bulbs. The diagram above shows the CORRECT way to connect the spliced wires.
The DC voltage (VDC) of the power accessory is as important as its AC voltage (VAC). When reading an adapter label, the VDC will be under the DC symbol. The AC symbol is a wave, while the DC symbol is a solid dash with three short dashes underneath it.
For light bulbs and heating elements, both AC and DC will work as long but the fact is that though all electric devices require direct current, alternating current is what is used to deliver electricity with the help of transformers which convert AC to DC for the use of electric devices.
Despite some of the most popular power supply voltage options being 12V or 24V DC, it's important to remember that (most) individual LEDs are actually 3V DC devices.
If you don't want to buy a battery-powered set, there are two ways to run your normal (120V AC) Xmas lights off batteries. The first is to use a 12V battery and an inverter.
The AC LED device is actually made up of two strings of series-connected die, connected in different directions; one string is illuminated during the positive half of the AC cycle, the other during the negative half.
You can bring your string of multicolored twinkling lights in either your carry-on or checked bags. Just make sure you don't get tangled up in them on the way through the security checkpoint.
The anode is the long protrusion on the bottom of the bulb through which current can enter, and it's positively charged. The current then passes through the bulb and goes into the negatively charged cathode (shorter leg) and out through another wire that leads back to the battery's negative end.
If one of your LED light strands isn't working, it's probably just because it has a bad bulb. If one bulb dies, it can cause the rest of the strand to stop working. The only way to fix the problem is to find the bad bulb. Sometimes only a section of the lights will go out, making your job pretty easy.
You'll note that it's actually two wires side by side. One wire has a slightly raised "rib" along one side. This is the "neutral" wire.
Transformer Problem – strings of Christmas lights require a transformer. This drops the amount of power back to a trickle, which is all the lights need to work. Sometimes, transformers die and need replacing. It is important to replace like with like.
There is a sliding door and it looks like this. Rhett Allain Fuses in a strand of Christmas lights. If you connect too many strands of lights together then the current will be too large. The fuse will go out to prevent these things from getting too hot.
A common choice when choosing an LED strip is either 12V or 24V. Both fall within low voltage lighting, with 12V being the more common specification.
Incandescent Mini Light Sets use 3 amp fuses. Heavy Duty light sets 5V use 3 amp fuses. C7, C9 light sets use 5 amp fuses.
Since each string is 40.8 watts, we know that each string needs 0.34 amps (40.8÷120).