Terminology/Definitions

This page is a constant work in progress as the hobby is constantly changing.

Contents: A * B * C * D * E * F * G * H * I * J * K * L * M * N * O * P * Q * R * S * T * U * V * W * X * Y * Z

A

AC — alternating current. An electrical current that reverses directions at regular intervals. Wall power, or mains, is AC and in North America, it cycles 60 times per second, while in England and Australia, it cycles 50 times per second.

Arduino. An Open Source system for developing microprocessor-controlled projects, including a reference design for a project board, as well as an integrated development environment (IDE) and linking to the Atmel firmware development chain. Further, a series of printed-circuit boards that can plug into the Arduino board — called “shields” — have been development for the project boards, extending the capabilities of the project environment.

ATmega. A brand of microcontroller developed and sold by Atmel Corp. The Arduino line of project boards uses ATmega microprocessors (the 168, 328p, 1280 and 2560, depending upon the Arduino model). ATMega chips have an entire different firmware development chain than chips from Microchip Technology and therefore can’t share code.

Amps (amperes). A unit of electrical current, an amp is the amount of electricity being drawn through the power system. A product that draws 10 amps uses twice as much electricity as a product that draws five amps. See also Electricity basics.

B

BNC — Bayonet Nut Connection. A type of common radio frequency connector used on coaxial cables. See RG-58.

C

C7, C9 light bulbs. Known as the “traditional” Christmas light, these types of strings had their hey-day in the 1950s and 1960s. Many lighting hobbyists switched to “mini” bulbs in the 1970s. The C7 bulb is about 2-inches tall, while the C9 is about 3-inches tall. The C7 uses the candelabra base, while the C9 uses the intermediate base (both of which are Edison screw-in types). Both sizes come in both clear and opaque colors and both come in 7-watt versions, while the C7 comes in a 2.5-watt version and the C9 in a 3.5-watt version. The maximum number of 2.5-watt lamps per 15-amp circuit is about 575 (or 765 lamps per 20-amp circuit) or 300 lamps per outlet, while the maximum number of 7-watt lamps per 15-amp circuit is about 200 (274 per 20-amp circuit) or about 125 lamps per outlet.

Capacitor. An electrical component that stores an electric charge and releases it when its needed. Typically used in Christmas lighting as a filter in power supply circuits.

Circuit. The path (usually wire) through which current flows between an electrical energy source and an electrical device, appliance or fixture.

D

dB — decibel. A unit of relative sound or radio transmission intensity.

DC — direct current. An electrical current that flows continuously in one direction. Batteries and fuel cells produce direct current and alternating current can be rectified and changed into direct current with diodes.

Decoupling capacitor. A capacitor that is included in circuits with microcontrollers to insure that voltages don’t dip and spike elsewhere around the circuit because of the needs of the microcontroller. Like a water tower in a community, the circuit slowly fills up the decoupling cap with electricity. When the microcontroller needs a burst of energy (or, in the analogy, if somebody needs to flush three toilets at once), the decoupling cap provides the needed energy without the water pressure throughout the community dropping.

Diode. An electrical device that will allow current to pass in only one direction.

DIP — Dual In-line Package. A method of mounting integrated circuits, microcontrollers and other electronics components on printed circuit boards. Sometimes called “through-hole package,” because holes are drilled in the PC boards and the package is soldered to the board on the side opposite the package. Compare this with “surface mount,” where components are mounted to the PC board on its top side by soldering leads directly to pads.

Dipole. A basic radio antenna that consists of two elements, each of equal length. The length of the elements is an algorithmic function of the frequency over which the broadcast is being made. It’s used in Christmas lights by FM transmitters that are used to broadcast music with the light shows.

Dirknerkle. The patron saint of this site. Dirk runs not only the forums and wiki, but also is the proprietor of Dirknerkle’s Inventorium and Generally Worthless Device Factory, an online store that provides items of greater or lesser interest to holiday lighting enthusiasts.

DMX (also known as DMX-512). Digital MultipleX. A theater and stage-lighting system based on the RS485 differential signaling electrical communications system that supports controlling light intensity across 255 steps. The system supports 512 different channels (called a “universe”) of lighting control and larger numbers of devices can be controlled by adding more transmitting controllers. Receiving controllers are daisy-chained together with each controller receiving and processing all 512 channels, but only acting upon those channels to which it has been assigned. Traditional DMX-512 uses five-pin XLR connectors, while in holiday-lighting Cat5 cable and RJ45 networking products have been adopted.

E

Electricity basics. The flow of electrons typically over wire, electricity is energy converted from fuels or natural resources and distributed to homes and businesses via a grid of utility companies. Electricity has three basic units: voltage, current (measured in amps) and resistance (measured in ohms). The basic equation of electrical engineering is that amps = volts divided by ohms. The fourth basic element of electricity is watts, which is volts times amps. The most common analogy used to describe electricity is that of plumbing and water: the pressure of water in a pipe is like voltage, while the flow of the water in a pipe is like amps.

Electrolytic. A type of fixed capacitor. See capacitor.

F

Farad. A unit of measurement for electrical capacitance. See capacitor.

FCC — The Federal Communications Commission. The FCC was established by the Communications Act of 1934 and is charged with regulating interstate and international communications by radio, television, wire (telegraph, telephone), satellite and cable.

FCC Part 15. A section of the Federal Communications Commission’s rules and regulations that deals mainly with unlicensed transmissions. In the Christmas light world, FCC Part 15 is discussed because it regulates the way low-power FM transmitters, which are used in the Christmas lights community to broadcast the music that accompanies the light shows, should work. The general consensus in our community is that one way of measuring whether an FM transmitter might meet Part 15 rules is that it should not transmit further than 250 feet away from its antenna.

Fuse. A device designed to make electronic and electrical circuits safer by breaking (“blowing”) in the event of an electrical short circuit or overload. A fuse will blow before wires become so hot they catch on fire.