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) that supports an easy-to-use programming language 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 developed 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.

Audacity. Open Source audio editing application available for a variety of personal computer operating systems. See http://www.audacityteam.org/.

AusChristmas. A web forum that focuses on Christmas lights in Australia.

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

BBB/BBG - Beaglebone Black/Beaglebone Green A system on a chip board, these are used for running falcon player (FPP) software to run your show. These microcomputers are very powerful and have numerous capes that attach to them allowing them to do a myriad of things for your show

BNC — bayonet nut connection. A type of common radio frequency connector used on coaxial cables. See RG-58.

Board. A shortened term for 'circuit board,' which is a thin layer of fiberglass or other material that has electrical circuitry fused to it. Electronic components are soldered to the 'board' circuitry to create electronic devices such as controllers.

BOM — bill of materials. A list of parts — including quantities, manufacturers and serial numbers — needed to build a specific project.

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 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. These terms have also been appropriated by LED Christmas-light makers and therefore C7 and C9 LEDs are also available.

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.

Cat3, Cat5, Cat5e, Cat6. Traditionally used as the cable in Ethernet networking, “Cat” is short for “category” and the numbers refer to different signaling standards. Cat5 cable has four pairs of 22- to 24-gauge wires, usually designated by the colors orange, green, blue and brown; each colored wire in the pair has a solid color and the same color with a white stripe. The orange/orange-white pair in Cat5 is twisted, while all the pairs in Cat5e and Cat6 are twisted.

Channel. In Christmas lighting, the method of identifying a lighting element in sequencing software. An element can be an individual lamp (such as in a smart pixel) or a string of lights.

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

Co-op. See group buy.

Color organ. An electronic device that takes in audio signals and automatically outputs digital signals that can be assigned to lights. While a color organ can be designed to respond to music, the result isn’t as appealing as a song sequenced by a person.

Controller. A device that accepts signals from a computer running a lighting sequencer and controls lights based on those signals (turning them on or off, dimming up or dimming down).

Current. The amount of electricity flowing through a circuit, measured in Amperes (A), milliamperes (ma) or microamperes (ua).

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.

DIGWDF Store The on-line store that once produced weird yet curiously helpful circuits, adapters and gizmos that helped DIY'ers create customized solutions to blinky-flashy problems. DIGWDF had three main engineers, Grelllbbb, Hngnnorrgg and Fffllleeennnkkk, and the three of them collaborated and do most of the creative work. Periodically they posted information in the forum in a language that has been termed "Lutefisk-ese." It's a somewhat phonetic language that takes getting used to, which seems somewhat consistent with the various weird adventures the engineers got into from time to time... And those are all meant to be taken tongue-in-cheek... What IS true however is that ALL profits from the DIGWDF Store, however small, were directed toward the expenses of running the diychristmas.org site and forum. Sadly, the DIGWDF Store closed operations on Dec 31, 2018.

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 light shows by FM transmitters to broadcast music.

DirkCheap. A concept and philosopy that Dirknerkle used to help lower the cost of participating in this hobby. It applies to several products the DIGWDF engineers created, such as the DirkCheapSSR, a no-frills 4-channel unit that is "dirt cheap" to make... In most cases, "DirkCheap" products used minimal parts due to their extra-sparse designs, such as no protective fusing or terminal blocks for convenience. It was the end-user's responsibility to address these issues on his/her own. The first product to carry this moniker was indeed the DirkCheapSSR, which lowered the DIYer's cost per A/C control channel by almost 70%, down to less than $1/channel.

Dirknerkle. The patron saint of this site. Dirk runs not only the forums and wiki, but also was the proprietor of The DIGWDF Store Dirknerkle’s Inventorium and Generally Worthless Device Factory, an online store that provided items of greater or lesser interest to holiday lighting enthusiasts. (based on sales totals, mostly lesser...)

DIYC. Can refer to either DoitYourselfChristmas.com or DIYChristmas.org.

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 telecommunications products have been adopted. Renard DMX is one implementation of the DMX protocol that's designed for Renard-type controllers.

E

E1.31. A digital standard protocol for transmitting DMX-512 data over Ethernet networks.

EDM Design. A South African company that makes low-powered FM transmitters. While these are sold in the United States as “kits” — a term used to skirt FCC regulations — 99 percent of the transmitter comes completed.

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.

Endless loop. A mistake in computer programming where instructions circle back and forth, never ending. See infinite loop.

Engineer. One who designs, builds, invents, maintains or otherwise creates or supervises processes, structures, machines, devices, materials and/or systems. At DIGWDF (see Dirknerkle), staff engineers include Fffllleeennnkkk, Grelllbbbb and Hngnnorrgg. They were supervised by Mr. Nerkle and Monica Momglobs, the DIGWDF receptionist.

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.

Firmware. The set of instructions input into a microprocessor. Firmware is usually developed on a personal computer, compiled into assembly code and uploaded to the microprocessor.

FM02. An inexpensive a low-powered FM radio transmitter that meets FCC Part 15 rule. Unfortunately, it was no longer manufactured after 2014. Also see Vastelec.

FPP - Falcon player Falcon player formerly known as Falcon Pi Player hence the fpp designation, is a linux based scheduling software ran on a Beaglebone Black or green (BBB/BBG) or Raspberry Pi system on a chip (soc) microcomputer. This is capable of running your entire show on one of these inexpensive boards. The Beaglebones have 1 usb and 1 ethernet out with no onboard sound, the Raspberry Pi's on the other hand have 2 to 4 usb outs, 1 ethernet out, and onboard sound, the latest version of the Pi has built in wifi.

Full wave. A method of converting AC to DC using a rectifying circuit of a group of four diodes, called a bridge. A bridge rectifier can be a single component.

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.

G

Gerber Files. - The standard file formats that PCB production facilities use to set up their equipment to manufacture the boards. Usually provided as a set of 8 or sometimes more files; each file describes a specific layer of the PCB, such as the top copper layer (GTL), bottom copper layer GBL), top solder mask (GTS), bottom solder mask (GBS), top silkscreen (GTO), bottom silkscreen (GBO), drill hole sizes (TXT or DRL) and a mechanical (outside dimension, GML) layer. Gerber files are generally produced by PCB design software as an export function.

GFCI — ground fault circuit interrupter. An electrical safety device installed in a power panel, sub-panel or outlet box that instantly shuts off the electricity when a leakage to ground occurs. This leakage can increase the risk of electrical shock. A GFCI should be used in all outdoor high-voltage environments and the device should be tested on a regular basis.

Grelllbbbdweeno - A variant of the Arduino, this is a stripped-down version without the bells and whistles that can be used to build into projects. It was invented by Grelllbbb, one of the DIGWDF engineers.

Grounded/grounding. A conducting connection, whether intentional or accidental, by which an electric circuit or equipment is connected to the earth, or to some conducting body of relatively large extent that serves in place of the earth.

Group buy. Volunteers take the initiative to gather the components of a project and resell them to other hobbyists. Because electronics retailers and wholesalers frequently give quantity discounts, a group buy leverages the buying power of members of the community, delivering lower prices for a project.

H

HC595. A serial, shift-register microchip that can control up to eight different devices. HC595 chips can be connected in series, allowing for an almost infinite number of devices to be controlled through the serial output pin of a microcontroller. This microchip is made by a variety of manufacturers using a variety of different names, though they always have “595” in them.

Half wave. See full wave. In Christmas lighting, term used to refer to strings of LEDs that don’t have a rectifier included.

Heat sink. A piece of metal attached to an electronics component — microprocessor, microcontroller, Triac, optoisolator — that serves to dissipate or absorb unwanted heat. Many electronics components have two ratings, a lower one when a heat sink is not used and a higher one where a heat sink is in place. Also called a dissipator. (Note: This term is often misspelled as "heat sync" which doesn't make any sense at all.)

I

IC — integrated circuit. An electronic component in which many elements are fabricated and interconnected by a single process (into a single chip), as opposed to a “nonintegrated” circuit in which the transistors, diodes, resistors and other components are fabricated separately and then assembled. Elements inseparably associated and formed on or within a single substrate.

Infinite loop. A mistake in computer programming where instructions circle back and forth, never ending. See unproductive loop.

J

Jumper. A connector on a printed circuit board that allows two parts of a circuit to be completed. Also, a short length of wire to complete a circuit.

K

Komby. A holiday lighting system based on the Arduino platform that sends lighting commands wirelessly via 2.5MHz radio frequency using the nRF24l01 transceiver. Input can be in a variety of protocols (Renard, DMX-512, E1.31) and various outputs are also supported (Renard, DMX-512, smart pixels). Named after hobbyist Greg Scull, the primary developer, whose childhood nickname was “Komby.”

L

LED — light emitting diode. A solid-state, semiconductor device that converts electrical energy directly into light. LEDs show up in Christmas lighting in two contexts: the first is as a power or signal indicator in controllers or SSRs, while the second is their use as a substitute for incandescent lamps. LED Christmas light strings use about one-tenth the energy of an incandescent lamp and have an extraordinary life span (some makers claim as many as 20,000-50,000 hours of use).

Lutefisk. The main dish in the official Christmas holiday meal of DIYC.org; a Scandinavian delicacy. Lutefisk is cod fish that has been air-dried to preserve it. Prior to cooking, it must be reconstituted by soaking for days in a lye solution and then rinsed thoroughly before being cooked for the meal -- preferably steamed. It has the consistency of a gelatin dessert -- some call it "fish jello." It is said that half the Scandinavians who came to America came to escape lutefisk and the other half came to proselytize on its behalf. In any event, it's truly something of an experience... The three stages of eating lutefisk are as follows:

Lynx. A group of holiday lighting products developed by hobbyist Robert Jordan. Initially based on DMX-512, the Lynx product line now supports both wireless transmissions as well as driving smart pixels. The most popular of the Lynx products is the Express, a 16-channel AC controller.

M

M5. A type of LED Christmas light that is modeled after mini-lights. Typically, an M5 has a faceted cover and 110v AC strings come in 30, 50, 70, 90, 100 or 120 bulbs. These strings are made of combination series/parallel circuit construction and use resistors to compensate for the difference between the total bulb count and the input voltage. Commercial M5 strings are usually full wave, while hardware or drug store strings are usually half wave.

Mains. The alternating current electricity provided by the utility company; a Britishism/Aussy slang for the American phrase “wall power.” In North America, typically 120 volts, AC. In the United Kingdom and Australia, typically 240 volts, AC.

Microchip Technology Inc. Maker of the PIC line of microcontrollers.

Microcontroller. A computer-on-a-chip that emphasizes high integration, low power consumption, self-sufficiency and relatively low cost. Typically, a microcontroller has flash-type read-write memory allowing a programming station (usually called a PIC programmer) to enter in task-specific programs, which can be written in programming languages such as C, C++, BASIC or even in assembly code (which, of course, is the most efficient).

Mini-lights. Holiday lighting incandescent bulbs that are about 7/32nds of an inch in diameter, they come in strings as short as 35 bulbs and as long as 400 bulbs, officially known as the T1-3/4. The strings are wired in series and parallel, usually in 50-bulb groups (the 50 bulbs are in series which are then wired parallel to the others, making 100-, 150-, 200-, 250-, 300-, 350- or 400-bulb strings). Pretty universally, strings that are grouped by 50 bulbs can be cut down to single 50-bulb strings. Mini-lights that are grouped by 50s use 2.5-volt, 170 mA bulbs, while 35-bulb strings use 3.5-volt bulbs. Colored mini-light bulbs are traditionally painted with a transparent paint, which can under certain weather conditions chip or fade.

MOC3023. A 6-Pin DIP 400V Random Phase Triac Driver Output Optocoupler from Fairchild Semiconductor. It provides both Triac services and optoisolator services in one package.

MORON. What other DIY'ers will think of you if you don't RTFM (see below).

N

nRF24l01. A type of digital radio transceiver that supports transmission rates up to 2 megabits per second, using the 2.4GHz frequency, manufactured by Nordic Semiconductor. The radio is made as a 4mm x 4mm QFN surface-mount chip and requires certain additional components to operate. It only became popular when it was packaged in a small, pre-built printed circuit board with an antenna (or antenna connector) and an eight-pin connector. Has an effective range of about 250-500 feet in line-of-site environments. Used in the Komby line of wireless Christmas-lighting controllers.

NOP. A "no-op" or "no-operation" command is often used in assembly language programming to cause the CPU to use-up one or more clock cycles just doing basically nothing. In this way, one can tweak the exact timing of a chip's CPU to better match a needed circuit function.

Null pixel. In instances where the first pixel of the display and the controller are too far apart, a “null pixel” is included halfway in between in order to boost the signal. The device is usually just the pixel controlling chip without the LEDs.

O

Ohms. The measure of resistance to the flow of an electric current (the resistance through which one volt will force one amp). Resistors in electronic circuits are measured in ohms, as is the voltage drop of an electrical wire. See also Electricity basics.

Optoisolator (opto, optocoupler). A device that insures that a non-electrical barrier exists between a high-voltage environment and a low-voltage environment. It usually has some type of emitter — like an LED or a neon bulb — and an optical receiving element with a little dark tunnel between them. The high voltage causes the LED to brighten and that light then drives the low-voltage optical receiver. This way wall plug voltage doesn’t stream down low-voltage wires and into your controller or PC.

Oscillator. A circuit that produces a sustained AC waveform with no external input signal. Oscillators can be designed to produce sine waves, square waves, or other wave shapes. They are typically used in Christmas lighting to produce fading and dimming.

P

PCB — printed circuit board. An electronics board that contains layers of circuitry that connect the various components of a system. A PCB can be mass manufactured or can be “home etched,” where a hobbyist transfers the design of the PCB to a copper-clad board, uses caustic chemicals to etch away the areas not needed and then drills the holes him or herself.

PIC. A brand name for microcontrollers from Microchip Technology Inc., it has become a generic term for any microcontroller, which is a computer-on-a-chip. Importantly, the development chain for the PIC is different from that of other microcontrollers (such as the ATmega series), so the underlying code of firmware cannot be shared between chip families.

Pixel. In computer graphics, a picture element. On most digital screens, a single spot on the monitor. In holiday lighting, an LED that has three colors (red, green, blue), either controlled as a group (“dumb pixels”) or as a single element (“smart pixels”). Holiday-light pixels are available in a number of form factors, including strips, strings of rectangular pixels, strings of “bullet” pixels, strings of “square” pixels and strings of “C9” pixels.

POD — power over DMX. Using RJ45 connectors and Cat5 cabling, 12-volt power is sent over three of the eight pairs of wires, while DMX-512 signal is sent over two of the wires. The orange and orange-white wires carry the DMX, while the solid green, blue and brown wires carry 12-volts negative and the white-green, white-blue and white-brown wires carry 12-volts positive. Developed by Dave Moore of HolidayCoro.com.

Polarity. The electrical condition of being either positive or negative. The direction of current between two leads or the direction of a magnetic field.

Programmer. A device that connects to a personal computer to a microcontroller to download an application from the PC to the chip. See PIC.

Protocol. The data "language" that is used between devices so that they can communicate with one another. Examples are RS-232, RS-485, RS-422, Ethernet, Renard, DMX, E1.31, SACN, etc. Devices must be using the same protocol to be able to communicate. For example, a device that's sending data in the RS-232 format cannot be understood by a device that's expecting to receive DMX data.

PWM — pulse width modulation. A method of controlling analog devices with digital signals; used in dimming lights and the speed of small DC motors. Rather than increasing or decreasing voltage, PWM controls the number of time segments the full voltage is applied (in microseconds).

Q

Question. Things that you are free and encouraged to ask about the hobby or how to do it. Answering them is what our users are here to do. Our motto is, "There's no such thing as a dumb question."

R

Ramsey Electronics. former maker of FM radio transmitter and other electronic kits. Ramsey is out of business but some of its kits are carried by HobbyTron: HobbyTron

Raspberry Pi. A full UNIX-based computer the size of a bar of soap. The Pi uses a system-on-a-chip (SoC) from Broadcom and has full USB, memory card, HDMI video output and audio input/output support. In holiday lighting, used in conjunction with the FPP software, which schedules and plays lighting sequences.

RDM — remote device management. An expansion to the DMX-512 protocol for configuring, updating and maintaining lighting equipment by allowing that equipment to send data back to the controlling computer.

Resistor. A component in an electrical circuit that controls current by providing resistance. See ohms.

Renard. A method of controlling holiday lights using a microcontroller as an interface between a personal computer and the lights, conceived by hobbyist Phil Short in 2006. Renard is three things: controller hardware designs; the firmware running in the microcontroller, and the serial protocol for sending the commands from the personal computer to the lights. The initial hardware design was for eight channels and controlled two, four-channel SSRs using a Microchip PIC 16F688 processor. Renard controllers are designed by a variety of hobbyists and are available as printed circuit boards or as kits (which can be found here, here, here, here or here). The name “Renard” is a play on the French slang for a male fox; in 2006 the leading DIY Christmas light sequencer was Vixen, which while the name of one of Santa’s reindeers in the poem “A Visit from St. Nicholas,” is also a word describing a female fox.

RG-6, RG-8, RG-11, RG-58, RG-59. These are all coaxial cables of varying thicknesses and impedance. The RG stands for “radio guide,” an old, obsolete military specification; the numbers are arbitrary. Most coax manufactured today is “RG-xx type,” because manufacturers don’t necessarily always meet the precise specifications. In the Christmas light world, you will encounter RG-58, a 50-ohm cable, because it is used in radio transmission and is discussed along with low-power FM transmitters that broadcast the music that accompanies the light shows.

RGB — red, green, blue. A color model typically used in light applications (other color models include hue, saturation and lightness — HSL — and hue, saturation and value — HSV — as well as cyan, magenta, yellow, black — CMYK). In Christmas lighting, it is a term frequently used to designate a pixel, which has three LEDs, each of the named color. Note that the physical wiring order of different pixel types may be in RGB order, or RBG, or GBR, or GRB. Therefore the term RGB is a descriptive term, not necessarily a standard.

RJ45. Registered Jack 45 is a telecommunications or computer connector that has four pairs of wires, for eight conductors. Wires can be attached in two different patterns, AT&T T568A or AT&T T568B.

RoHS — restriction of hazardous substances. A directive by the European Union that is designed to keep harmful chemicals and materials to a minimum. It is used by electronics manufacturers to denote components that meet the EU requirements.

RS232. A telecommunications protocol, Recommended Standard 232 was originally designed to connect teletypes with modems; it has survived to this day as the way computer serial ports send out data. RS232 is implemented in a variety of connectors, but is most commonly seen in the DB9 and DB25 devices. It uses nine wires and supports transmitted data, received data, request to send, carrier detect and ring indicator. It is used in Christmas lights by as the physical layer between PC serial ports and Christmas lights controllers.

RS485. A telecommunications protocol, Recommended Standard 485 is typically used in building automation, the programming of logic controllers, sound system control, lighting control and video surveillance camera control. It is a two-wire system that uses a differential form of signaling that supports the transmission of data packets. It can be used over a long distance and supports multi-point connections. It is used in Christmas lights as a distribution system for light controllers signaling devices, sometimes using the DMX512 or the Renard protocols.

RTFM A long-standing acronym in the tech community that stands for "READ THE F***ING MANUAL." Many DIY projects available in this community do have accompanying user guides, assembly manuals and other printed documentation. Don't be a moron -- when documentation is available, take the time to read it and follow it. It's there for a reason.

S

Sequencer, sequencing. A computer program that allows hobbyists to align and apply lighting commands to music, or the process or using such a program. An early Christmas lighting sequencer was Comet, which was followed by Vixen (which has branched into two offerings, Vixen3 and VixenPlus). Other freeware sequencers include HLS and Nutcracker/xLights. Commercial sequencing applications include Light Show Pro and Madrix.

SMT, SMD — surface-mount technology, surface-mount device. A type of printed circuit board assembly that uses components that are soldered directly to the top of the board, rather than through holes drilled in the board. Most hobbyists view it as a more challenging technique than through-hole assembly. See also DIP.

SNR — signal to noise ratio. A measure of signal strength relative to background noise. In Christmas lights, would be used in conjunction with an FM transmitter, that itself would be used to broadcast music with the light shows.

SPT — service parallel thermoplastic. A type of electrical wire, commonly referred to as “zip cord” or “lamp cord.” Usually used in conjunction with the numbers 1, 2 or 3, which indicate 64ths-inches of insulation. SPT1 is usually 18 gauge wire, while SPT2 is available as 16 or 18 gauge and SPT3 can be as large as 10 gauge.

Start channel. In DMX or wireless environments, the first channel a receiver has been programmed to accept. For example, a four-channel DMX receiver might be set to receive only channels 8-11, though all 512 channels pass through it, so its start channel would be 8.

SSR — solid-state relay. In general electronics, an digital switch, rather than a switch with mechanical parts. In Christmas lighting, a light controller that includes a solid-state relay.

Surface mount technology; surface mount device (SMT, SMD). A method of mounting integrated circuits, microcontrollers and other electronics on printed circuit boards. The method mounts the devices on the top of a PC board rather than using holes through the board. Compare this with DIP.

SWR — standing wave ratio. Usually used in the phrase “SWR meter,” which is a device coupled between a radio transmitter and an antenna and is used to tune the antenna accurately to the frequency over which the radio waves are being transmitted.

T

Transformer. An electro-magnetic device designed to raise or lower electrical voltage.

Transistor. A basic solid-state semiconductor that has three terminals and can be used for amplification, switching and/or detection.

TRIAC — triode for alternating current. An electronic component used to turn on and off AC power to an electrical device such as a Christmas light. Specifically designed to handle dimming circuits.

Twisted pair. Two insulated wires bent and curled together. Usually used in electronic signaling such as RS232 and RS485.

U

ULN2803. An array of eight Darlington transistors (which themselves are arrays of two transistors) that amplify current. Often used in Christmas lights as devices to increase the current coming from a microcontroller to an SSR so that there is enough power to turn on (or off) the SSR.

Universe. In DMX, 512 channels of lighting.

Unproductive loop. A mistake in computer programming where instructions circle back and forth, never ending. See endless loop.

USB — universal serial bus. A type of connection typically found on a personal computer linking peripheral devices to the computer. It is a four-wire serial interface that includes 5-volt, DC.

V

Vastelec. Maker of FM radio transmitters, with divisions based in Hong Kong and Zhuhai, China.

Vixen. One of Santa Claus’ “eight tiny reindeer” as defined in the 1823 poem, “A Visit from St. Nicholas” (also known as “The Night Before Christmas” or “’Twas the Night Before Christmas”). Also, the name of a light-sequencing application initially developed in 2006 by hobbyist K.C. Oaks, who on his own wrote versions 1, 2, 2.1 and 2.5. In 2013 he wrote the underlying code for Vixen 3 and then turned development over to a group of volunteers. Also in 2013, a parallel project was started by John McAdams, which he calls VixenPlus.

Voltage drop. The loss of electrical voltage in a circuit which is determined by two main factors: the size of the wire (or wire gauge) and the length of the wire run. While it can be experienced in any circuit, it typically is more of a problem in lower voltage circuits (5 volts-24 volts). Voltage drop on a long run of wire can be helped by increasing the wire gauge, using a smaller AWG number wire.

Voltage regulator. An electronic device designed to take a higher voltage and make it conform to a specific lower voltage. Provide a 5-volt regulator with 12 volts as an input and it will put out a steady 5 volts; provide a 12-volt regulator with 13 volts and it will output a steady 12 volts. While some regulators are designed for specific voltages, others can provide a range of voltages depending upon resistance applied; variable voltage regulators can be controlled by potentiometers (i.e.: volume control), so that you can turn a knob and get various voltages depending on where the knob is.

Volts. A measure of “electrical pressure” between two points in a circuit. The higher the voltage, the more current will be pushed through the circuit. See also Electricity basics.

W

Wall power. The alternating current electricity provided by the utility company. In North America, typically 120 volts, AC. In the United Kingdom and Australia (where it’s known as “mains”), typically 240 volts, AC.

Watts. A measure of the amount of electrical power drawn by a load, such as a light bulb. A watt is determined by multiplying volts by amps. A kilowatt is 1000 watts and electrical utilities measure electricity consumption by kilowatt hours. For example, if you have two 500-watt heaters, and you leave them both on for one hour, you have used one kilowatt hour of electricity. See also Electricity basics.

Williams, Carson. An early Christmas light show hobbyist, Williams videotaped his sequence of the song “Wizards in Winter”, by the group Trans-Siberian Orchestra in 2004 and posted it on YouTube. The video gained millions of viewings in 2005 and helped launch the popularity of computerized Christmas lights shows sequenced to music.

Wire gauge. A way of measuring the diameter of a wire. It is determined by the number of times a piece of metal is passed through successively smaller dies. So, the smaller the number (2, 4, 6, 8) the larger the diameter of the wire, while the larger the number (18, 22, 24), the smaller the diameter of the wire. Frequently expressed as AWG, meaning American Wire Gauge.

Wireless. Radio transmission of signals. In holiday lighting, a method of transmitting sequences over a low-power radio such as an xBee or nRF24l01.

X

XBee. A type of digital radio transceiver that supports transmission rates up to 250 kilobits per second, manufactured by Digi International Inc. Available in a variety of output powers (up to 100 mW), topologies (point-to-point, star, mesh) and frequencies (868, 915 or 2450 MHz) using the ZigBee transmission protocol.

Y

YMMV. - An acronymn for "your mileage may vary," a term often used by DIY'ers when suggesting that a measurement or experience of some kind may not be consistent with what one person is describing.

Z

Zero cross. A technique for dimming AC lights which determines the point at which an AC line oscillates at zero volts. Employing the technique is necessary to allow AC lights to dim accurately. Other terms are zero cross detection, zero cross signal, ZC signal...

ZigBee. See XBee.