Twinkle bulb facts for kids

A twinkle bulb is a special light bulb that blinks on and off. They are often used for decoration. You usually see them on Christmas lights and other string lights. They can also light up things like electric jack-o-lanterns for Halloween.

How Incandescent Twinkle Bulbs Work

The first twinkle bulbs were a type of incandescent bulb. They had a special part inside called a bimetallic strip. This strip is made of two different metals joined together.

When the bulb gets warm, the strip bends slightly. This bending pulls it away from a contact point. When the contact breaks, the electricity stops flowing through the bulb, and it turns off. As the bulb cools down, the strip bends back. It touches the contact again, and the bulb lights up.

This process repeats over and over. The blinking might seem to speed up or slow down. Each bulb can blink a little differently. This is because of small differences from when they were made. If you use a dimmer to make the lights less bright, they might blink less or stop completely. This is because the blinking depends on heat.

When many of these bulbs are used on a Christmas tree, they create a sparkling effect. You might have seen these lights in big stores like Macy's. Even though they are harder to find in local shops, you can still buy them online.

Flasher Bulbs: A Special Type

Later, smaller twinkle bulbs were made. These were called flasher bulbs. They could turn off a whole string of lights, usually 10 to 50 bulbs. These bulbs are easy to spot because they have a red tip. The rest of the bulb is clear.

Flasher bulbs come in different voltages. This means they work with different sizes of light sets. Some older light sets had two separate circuits. This meant that some lights would stay on while others blinked off. For example, all the odd-numbered bulbs might be on one circuit, and the even-numbered ones on another.

When flasher bulbs are used in battery-powered lights, each bulb flashes by itself. This also helps the batteries last longer. This is because the bulbs are off for part of the time. Some AC light sets, like NOMA "Stay Lit" lights, also let individual bulbs flash. This happens because of a special part called a shunt in the socket.

Sparkling Bulbs: Faster Flickering

In the late 1900s, flasher bulbs were changed. The bimetallic strip was designed to be "normally open." This means it doesn't touch the contact when it's cold. When you first turn them on, electricity flows through the bulb's filament. After a few seconds, it warms up.

Then, the strip quickly makes and breaks contact. This creates a quick, low-resistance path around the filament. This makes the bulb flicker very fast. It's much faster than most other twinkle or flasher bulbs. The steady bulbs nearby might also flicker a little in response.

These 6-volt bulbs were often used in 35-light sets. They were placed in every other socket, alternating with steady 6-volt bulbs. Brands like General Electric and Macy's sold them.

Newer sparkling bulbs made in the 2010s are different. They have fewer twinkling bulbs, usually only one out of five. The other four bulbs are steady. These steady bulbs have the expected voltage for the light set. However, the twinkle bulbs are still 6-volt. Unlike older sets, modern sets usually don't have different sockets for the two bulb types. This is because there are so few twinkling bulbs.

How LED Twinkle Bulbs Work

LEDs also have twinkling versions. But they work differently from incandescent bulbs. LED twinkle bulbs have a tiny electronic part called an oscillator. This oscillator turns the LED on and off at very regular times.

Dimmers or low batteries usually don't change how often LED twinkle bulbs blink. Just like with incandescent bulbs, being off part of the time helps batteries last longer.

LEDs start blinking right away when you turn them on. Because of small manufacturing differences, their blinking speed can be slightly off. When you see many LED twinkle bulbs together, they might look like they are blinking randomly. Sometimes, small groups might seem to blink together for a moment, like turn signals on cars waiting at a light.

Some LED twinkle bulbs can even change colors. They might switch between two colors, like red and green, or blue and white. These bulbs actually have two LEDs inside one clear casing. Other advanced LEDs can change brightness like a candle flame. They can also fade between two or three colors. But these are not usually called twinkle bulbs. They are often used alone, not in strings.

When LED lights flash or change colors together, it's usually because of a control box. This box sends signals to the bulbs. Some LED bulbs have two colors wired in inverse parallel. This lets them respond to changes in electrical polarity from the control box.

Blinking LEDs need direct current (DC) to work. This is the type of electricity from an electrical battery. If they use regular alternating current (AC) from a wall outlet, the oscillator would constantly reset. To fix this, mains-powered LED lights usually have a small rectifier or capacitor in their plugs. These parts smooth out the electricity. This also stops the light set from flickering with the electricity's frequency. Some twinkling LED bulbs can do this conversion inside the bulb itself.