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glossary:glossary_a [2013/04/16 19:13]
Bob Vetterlein
glossary:glossary_a [2019/09/10 07:42] (current)
tgerbic [Amps] Changed to a more useful answer.
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-Alternating Current ​Generally ​with a sinusoidal wave form. Mains power in Britain and Europe is 230v AC at 50Hz, that is 50 complete cycles per second. ​USA uses 115v at 60Hz.\\ ​+Alternating Current. Refers to a situation where current flows back and forth through a conductor (wire) in alternating directions. ​Generally, the voltage being applied to the conductor has a changing (alternating) polarity so the current has to change direction related to which end of the wire is positive or negative at a given point of time. In most cases we encounter, the voltage moves in a sinusoidal wave shape centered at zero volts, though it could be centered at another pointIf it is centered at another point than zero volts, it is most often referred to as having a voltage offset. An AC voltage could have another wave shape besides sinusoidal depending on the application or components it is reacting with. The rate at which it changes direction is referred to as its frequency. 
 + 
 +The opposite of AC is DC where the current only flows in one direction. DC will have a voltage level in only one direction, either positive or negative, referenced to a common, ground or zero volts reference point. 
 + 
 +Mains power in many countries such as Britain, Australia ​and Europe is at 230v AC at a frequency of 50Hz, that is 50 complete cycles per second. ​North America ​uses 115v at 60Hz. 
 +\\ 
 [[http://​www.allaboutcircuits.com/​vol_2/​chpt_1/​1.html|http://​www.allaboutcircuits.com/​vol_2/​chpt_1/​1.html]] [[http://​www.allaboutcircuits.com/​vol_2/​chpt_1/​1.html|http://​www.allaboutcircuits.com/​vol_2/​chpt_1/​1.html]]
  
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-[[:glossary#dcc_digital_command_control|DCC]] decoders are used to control trackside accessories such as turnouts and signals using the NMRA standard pulsed signal. The signal can be carried by the track and track feeders or can be a separate circuit, which avoids the risk of a derailment or short preventing the control of the turnouts. All DCC manufacturers make accessory decoders and MERG provide kits.\\  +**[[glossary:glossary_d#dcc|DCC]]** decoders are used to control trackside accessories such as turnouts and signals using the NMRA standard pulsed signal. The accessory decoder is controlled similar to a train decoder using a unique decoder address and a series of function variables. The signal can be carried by the track and track feeders or can be a separate circuit, which avoids the risk of a derailment or short preventing the control of the turnouts. ​ All DCC manufacturers make accessory decoders and MERG provide kits.\\  
-http://​www.merg.org.uk/​merg_resources/​dcc.php+https://​www.merg.org.uk/​merg_resources/​dcc.php
  
  
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-The MERG DCC accessory encoder is designed to operate as a DCC command station independently from the track DCC although it uses the NMRA Standard for its information encoding and can operate most other accessory decoders as well as the MERG kits.\\  +The MERG DCC accessory encoder is designed to operate as a DCC command station independently from the track DCC. It uses the NMRA Standard for its information encoding and can operate most other accessory decoders as well as the MERG kits.\\  
-http://​www.merg.org.uk/​merg_resources/​dcc.php+https://​www.merg.org.uk/​merg_resources/​dcc.php
  
  
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-Address is the unique identification of anything. In the context of DCC it means the coding of each loco or other decoder, which ensures that it identifies the signals intended for it.+Address is the unique identification of anything. In the context of DCC it means the coding of each loco or other decoder, which ensures that it identifies the signals intended for it.  
 + 
 +You will encounter two address ranges in the NMRI DCC standard, two-digit addressing (called short addressing) and four-digit addressing (called long or extended addressing). The number of digits refers to how many hexadecimal digits are transmitted/​received for a decoder address from the DCC system. A two-digit address can have hex numbers between 01 and FF (1 to 127 decimal). A four-digit address can have from 0001 to 27FF (1 to 10239 decimal). Many model railroad users use four-digit addressing in order to match up the DCC address with the four-digit train engine number to make it easy to remember the number to control the engine. ​ So, if the engine number is 1234, the train decoder will be set to 1234 as well. Generally address 00 is reserved in each number system for analogue operation and is also known as the Broadcast Address.  
 + 
 +DCC decoders store the addresses in Configuration Variables (CVs). Each decoder vendor may have different set of CVs to store the digits. Refer to the docs that came with your decoder.  
 + 
 + 
 +===== Agile ===== 
 + 
 + 
 +Agile is a Manifesto for Software Development. It aims to deliver working software quickly. See 
 +[[http://​agilemanifesto.org/​|the Agile Manifesto]] and its [[http://​agilemanifesto.org/​history.html|history ]]
  
  
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-An Amplifier is a device ​which uses a small amount of power to control ​source of large amount of energy+An Amplifier is a device ​or circuit that converts ​a small signal, voltage or current, into larger signal, voltage or current. ​ Amplifiers are typically built from discrete devices like tubes or transistors,​ or are manufactured as IC device to reduce components or complexity
  
 +You will generally run into three amplifier types on the MERG forum or with MERG kits; a transistor as an amplifier, an Operational Amplifier (op amp) such as an LM324 or an audio amplifier such as an LM386. ​
  
-===== Amplitude modulation (AM) ===== 
  
 +===== AM =====
  
-The process of additively mixing a single or number of frequencies with the carrier wave to produce a complex waveform with variable amplitude. This signal may be demodulated by a simple diode detector. Most common method for low, medium and high frequency broadcast transmissions. 
  
 +Amplitude Modulation. The process of additively mixing a single or number of frequencies with the carrier wave to produce a complex waveform with variable amplitude. This signal may be demodulated by a simple diode detector. Most common method for low, medium and high frequency broadcast transmissions.
  
-===== Amps ===== 
  
 +===== Amps or Ampere =====
 +
 +
 +An ampere is a measure of current flow. It is roughly defined as 6.28 X 10^18 electrons passing a point in one second. From a formula perspective one amp equals one volt divided by one ohm. If you had a one volt battery connected across a one ohm resistor, you would expect to measure one amp of current flow around the circuit. ​ Current values are often shown in formulas and on datasheets with the letters “A”, mA or uA.  In formulas current is generally shown as the letter “I”. For example E = I x R.  The letter “I” would most often be a value in amps, milliamps or microamps. ​
 +
 +In the model railroad context, you would expect to see a DC supply or a DCC booster providing several amps of current to a track, and most other circuits ​ or LED signals using ones to hundreds of milliamps. ​
 +
 +In a home environment,​ you would expect to see outlets in the 13 amp to 20 amp range and mains breaker panels working in the 50 amp to 200 amp range. ​
  
-The unit of current. It is defined as the constant current which if maintained in two straight parallel conductors of infinite length, of negligible cross-section and placed one metre apart in vacuum, will produce between the conductors a force equal to 2×10-7newton per metre length. 
  
  
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-===== And =====+===== AND =====
  
  
 This is a Boolean operator which is used to join two statements so that the final statement is true only if the individual statements are all true. Thus (X>​1)AND(X<​2) is true if X is between 1 and 2. In electronic logic circuits an AND circuit is shown [[logicgates#​and|here]]. This is a Boolean operator which is used to join two statements so that the final statement is true only if the individual statements are all true. Thus (X>​1)AND(X<​2) is true if X is between 1 and 2. In electronic logic circuits an AND circuit is shown [[logicgates#​and|here]].
 +
 ===== API ===== ===== API =====
  
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 [[wp>​API]] [[wp>​API]]
  
 +===== ASCII ===== 
 +American Standard Code for Information Interchange 
 +[[glossary:​asciicode|Table of Codes]]\\  
 +[[http://​en.wikipedia.org/​wiki/​ASCII|Wikipedia article]]
 ===== Aspect ===== ===== Aspect =====
  
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-===== Auto reverse ​=====+===== AT-Bus ===== 
 +An alternative CAN Bus protocol devised by MERG member Roger Edwards which overcomes what he sees as deficiencies in the [[glossary:​glossary_c#​cbus|CBUS]] protocol.  
 + 
 + 
 +===== Auto Reverse Module ​=====
  
  
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 ===== AWG ===== ===== AWG =====
  
 +American Wire Gauge is a set of standard sizes for wire diameter. It covers both solid and stranded wire.
  
-American Wire Gauge- This is not the same as Standard Wire Gauge. There is no direct conversion in that the ratio of radii SWG/AWG varies from 0.8 at 6/0 to 1.64 at 43.\\ +As the gauge number gets larger the wire diameter gets smaller. Larger wire is generally used for carrying higher current levels since larger wire has less resistance and so for higher currents less voltage is dropped over a given distance.  
 + 
 +In North America, extension cords are generally wired with 16AWG or 14AWG. House outlet wiring would generally have 14AWG or 12AWG wiring. In the UK, Australia and many other countries 2.5mm or 4mm wiring would be used in a similar fashion. Bus wires for DC or DCC may use large gauges such as these to supply a fairly constant voltage level (provides a low voltage drop over distance) around a large layout. Feeders to a track would be much smaller wires as current demands would be smaller. Relay coils and small wattage transformers may have gauges from 18AWG down to 28AWG. Wirewrap wire is generally 26AWG. While this paragraph is fairly general, it will give you an idea what to expect for wire sizes on a layout or simple projects. Better detail and recommendations can be found elsewhere in the Forum for a specific task.  
 + 
 +AWG is not the same as Standard Wire Gauge. There is no direct conversion in the ratio of wire diameter between ​AWG and SWG. 
 + 
 +\\ 
 [[http://​www.hardwarebook.net/​table/​AWG.html|http://​www.hardwarebook.net/​table/​AWG.html]]\\ ​ [[http://​www.hardwarebook.net/​table/​AWG.html|http://​www.hardwarebook.net/​table/​AWG.html]]\\ ​
 [[http://​www.simetric.co.uk/​siwire.htm|http://​www.simetric.co.uk/​siwire.htm]] [[http://​www.simetric.co.uk/​siwire.htm|http://​www.simetric.co.uk/​siwire.htm]]
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glossary/glossary_a.1366139591.txt.gz · Last modified: 2014/11/11 13:27 (external edit)