Control technology :

Christmas lights can be animated using special "flasher" or "interrupter" bulbs or by electronic controller. Flasher bulbs use a bi-metallic strip which interrupts the series circuit when the lamp becomes hot. An electronic Christmas light controller usually has a diode bridge followed by a resistor-based voltage divider, a filter capacitor and a fixed-program microcontroller. The micro-controller has three or four outputs which are connected to transistors or thyristor which control interleaved circuits, each with lamps of a single color.

Controllers can be set up to change flashing or animation styles by pressing a button or turning a dial on the unit; others have only one pattern, but the speed of this pattern can usually be adjusted by turning a similar dial.

Most multi-function sets feature 8 to 16 moving light functions. Some very common functions are fading and chasing. More extravagant and less common functions are stepping on and 2-channel flashing. These lights usually come in sets of 140 or 150. This is because to give the chasing effect, bulbs must be arranged in 4 circuits of 35 (equals 140) or 3 circuits of 50 (equals 150). These light sets use even less power than a regular set of 150 because the lights are not always on, and therefore the bulbs do not get as hot.

Usually, computerized sets cannot be connected end-to-end. However, some newer sets contain special miniature plugs - a "female" plug is located at the end of the set, and a "male" plug is located between the control box and the beginning of the actual lights. By disconnecting the control box from one set, it can now be plugged into the end of an identical chasing set to produce a longer strand of chasing lights. These plugs generally have a twist-on locking feature similar to that found on garden hoses.

Fiber-optic Christmas lighting can also be animated electronically, particularly when the set incorporates LEDs. When an incandescent lamp is used, animation can created by means of a rotating color wheel.

Computer controlled outdoor displays have become a hobby for many homeowners. Using products such as Animated Lighting, D-Light, or Light-O-Rama, one can synchronize their lighting to music, or create highly-intricate animated displays.