How do multicolor Christmas lights work?

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With the holidays over, many of us are braving the elements to take down all those holiday lights. LED lights have largely taken over the market, but in some places, you can still get classic incandescent bulbs. There are some effects that LEDs can’t quite mimic yet. One of those is the magic of “twinkling” light sets, which [Alec Watson] explains in a Technology Connections video. Everyone has seen bulbs that flash, and strings that dim. But the twinkle effect until recently has been hard to describe.

Typical flashing bulbs use a bimetallic strip. As the filament of the bulb heats up, the strip bends, opening the circuit. Then the strip cools and closes the circuit again. Twinkling lights do exactly the opposite. The bimetallic strip shorts the bulb out rather than open the circuit. Twinkling sets also use a lot of bimetallic strip bulbs – typically every fifth bulb has a strip. The result of the bulbs being shorted out is that all be the bulbs in set see a higher voltage. This makes the entire strip shimmer in time with the flashing. That’s where the twinkling magic comes from.

It occurs to us that the voltage on the strip would be a great source of random seeds. Sure, you’d have to replace bulbs now and again, but how many people can say they get their random numbers from a set of Christmas lights?

If you’re curious how incandescent Christmas lights can blow and not take out the whole strip, check out this article about anti-fuses.

It is mid-December and the cold winter air is flurrying through the night. The bright, flashing lights illuminate the dark sky. It is December 24, 2018, and the night before Christmas. All of the different kinds of lights will shine, so that Santa Claus will see the landing zone. The computers are running and making sure the lights are on.The computers also control how much electricity is given to each strand of lights. It will be a magnificent night for everyone who is coming to see the light display.

Crazy Kinds of Lights

Christmas lights are made in many shapes and forms. The classic small, cone shaped Christmas lights are called incandescent lights. These lights act like regular old light bulbs with filament, just smaller. One fairly newer Christmas light is an LED. LED stands for Light Emitting Diode. LEDs work when enough electricity runs through the light bulb. The electrons in the bulb reconnect with electron holes to create the light. Another newer kind of Christmas lights are RGBs. These Christmas lights have three LEDs inside them. As you might have guessed, RGB stands for Red, Green, Blue. The three LEDs inside are one red, one green, and one blue. The three LEDs inside the light, work together to create any color you want. The three lights inside shine at different frequencies to make different colors. Christmas lights come in many colors and sizes. Most newer Christmas lights are either in multicolor or in clear color forms. Multicolor Christmas lights come in a pattern using the colors blue, green, orange, red, yellow, and sometimes pink. The pattern works because the first light could be colored green, the second light being colored blue, the third light being orange, and so on until the pattern repeats. Clear lights are the color of their name, clear. These lights look like there is snow on houses when hung because they kind of look light the are white. Both multicolored, and clear lights are translucent, which means humans can partly see through them. The old multicolored C9 light bulbs that look the closest to a light bulb, are usually what is called frosted. Frosted means that the light has a coating of color, but the coating is covered with another clear coating that does not allow people to see through the light bulb unlike clear and multicolored. Frosted lights are opaque, which means that humans can not see through them.

Computer Controlling

High-tech Christmas light displays are usually able to make the lights flash, and it makes them look like they are dancing on the house. This is done by controlling when the lights go on, or off with a computer. The computer sends signals to the lights in Serial Communication, which is in 1’s or 0’s. Let us say that the signal 0, meaning the lights are off, and 1, meaning the lights are on. The computer could send either a 1 or 0 to every set of lights on the house in a matter of less than half of a second. The signals 1, and 0 are also called binary. This is one of the most basic languages of code a computer uses. All Christmas lights have 256 different levels of brightness. The person programming the lights can put some lights at one level of brightness, while others are at a different level of brightness. All Christmas light displays are different, which is the best part about all light displays. Some programers have the lights start on at one side of the house, and fade the brightness all the way to the other side of the house. This is done by slowly changing the levels of brightness from not on at all, to fully on, and back down to not on at all again. Light displays are usually flashing, because when the lights are all fully on, they draw a lot of electricity, which costs a lot of money. This effect cuts down on electricity costs, because the lights are only on for a split second, so the don’t draw nearly as much electricity. This fading effect, can also be done on leaping arches. Leaping arches are PVC pipe that is wrapped in lights. The pipe is bent to make an arch-shape. The arches are wrapped in lights, so the lights start on at one end, and fade the brightness of the lights, so the light goes from one end to the other. Some light displays have the lights flashing, and play music that coordinates with the flashing lights. The music is usually classic, Christmas music. The music is sometimes put on its own radio channel, so when cars come by to watch the display they can tune in on the radio to watch the lights flash, and dance to the music. When the music suddenly gets loud, sometimes all of the lights flash on at one time for a quick moment of time. When the music has longer notes, that kind of sway, the lights could fade back and forth.

Electricity is Everything

Electricity comes in two different forms, AC currents, and DC currents. 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. DC currents only flow in only one direction. Most regular light bulbs run on DC currents. This is a basic concept that is used in RGBs and some LEDs. AC current is a little bit different. Instead of having a steady current like DC currents do, AC currents do not have a steady current of electricity. This process is like the light flashing on and off. What actually happens is the electricity is flowing one direction, and then suddenly starts flowing the other direction. Since the light is flashing, people would think that if there was an AC current light in front of them, they could see the flashing. If this would happen, the person would not see the flashing. The reason for this, is because the light flashes sixty times per-second. This is way too fast for the human eye to see, so the quick flashes look like regular light. AC currents are used in incandescent lights, and some LEDs. If a light display had no electricity, there would just be plastic, some glass, and copper wire hung up onto a house.

It is 12:00 am, and the Christmas lights are off. Santa Claus will be there soon to give the little kids their presents. All of the different kinds of lights are done shinning for now, and will be on in about 20 more hours. The electricity finally gets a break of powering all of the lights outside and inside the house. The computers are sleeping and coding files are closed, but will be opened again soon. The night goes dark again, so Santa Claus will need his landing elves to guide him onto the top of the house. In the morning, people will be sprinting out of bed to see what he left them.

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