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glossary:glossary_h [2019/09/05 19:14]
tgerbic added text for Hexadecimal or Hex entry
glossary:glossary_h [2020/05/08 00:18] (current)
tgerbic Clarify definitions and fix typos. Add Hysteresis term focused on electronics application. H0 is not HO.
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-===== Hall effect =====+===== Hall effect sensor =====
  
  
-This a transistor type that is affected by a magnetic field placed in close proximity     \\ See MERG TBs A7/2/ 3/ 4 merg members only+A Hall effect sensor is semiconductor device often looking like a small transistor. When the device encounters a magnetic field it generates a voltage. There are many uses for a Hall sensor such as measuring the speed of a fan or replacing the points in a automobile distributor (detects speed and position to fire the ignition). In the context of the MERG site, a Hall sensor might be used to detect a passing train, which would have a magnet mounted under it, to close crossing gates or change track signals.  
 +\\ See MERG TBs A7/2/ 3/ 4 (MERG members only)
  
  
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-Is means of control in your hand.     \\ {{:glossary:handset.jpg}} {{:glossary:92-cancab-c.jpg?direct&200|}}+A handset is usually controller you would use while holding it in your hand to control a train engine, turnouts or track animation 
 +\\ {{:glossary:handset.jpg}} {{:glossary:92-cancab-c.jpg?direct&200|}}
  
  
 ===== Handshaking ===== ===== Handshaking =====
-In information technology, telecommunications, and related fields, handshaking is an automated process of negotiation that dynamically sets parameters of a communications channel established between two entities before normal communication over the channel beginsIt follows the physical establishment of the channel and precedes normal information transfer.+ 
 +Handshaking is process that allows two or more devices to establish communications, and control data being passed between each device. A common example would be when a PC printer port communicates with a printer. A communication is setup and then the handshaking process controls the text being sent to the printer, to only send as fast as the printer can accept itYou may, for example, have seen "software" or "hardware" flow control handshaking as settings in a serial terminal program on a PC.  
 + 
 + 
 +===== Happening ===== 
 + 
 +A term devised and introduced in the documentation for the MERG Universal CANMIO, for an event that is internal to the module to distinguish it from an external event (on the bus). 
 +For instance, say input 1 changes from high to low. In early modules of the CBUS range this would simply produce an ON event with EN (Event Number) of 1. In the Universal code for the CANMIO it produces a 'Happening' event with a value that indicates input 1 ON. Through the configuration process this may be mapped to produce that same event or something entirely different.
  
 ===== HASL ===== ===== HASL =====
-[[https://en.wikipedia.org/wiki/Hot_air_solder_leveling|Hot Air Solder Leveling]]\\ HASL = hot air solder levelling - the bare copper of the etched PCB would soon oxidise and refuse to take solder, so a thin layer of "something" is added to make the shelf life longer. The standard HASL provided by Chinese manufacturers is leaded solder. More expensive options are lead free solder, organic solderable varnish stuff, nickel, or gold flash.+HASL, or Hot Air Solder Leveling, is a process of coating the bare copper of an etched PCB with something like solder or varnish (solder mask). This keeps the PCB traces from oxidising over timewhich makes the traces harder to solder to.  
 +The standard HASL provided by Chinese manufacturers is leaded solder. More expensive options are lead free solder, organic solderable varnish stuff, nickel, or gold flash.\\ 
 +[[https://en.wikipedia.org/wiki/Hot_air_solder_leveling|Hot Air Solder Leveling]]\\ 
 +  
 ===== Header plug or socket ===== ===== Header plug or socket =====
  
  
-Are plug & sockets primarily for use on PCB boards to make connections to and from the board\\+A header plug is generally a row of pins soldered to a PCB. A header socket is a mating connector that plugs onto a header socket. This is a common way of interconnecting two PCBs, or a PCB with an LCD module. You may also find header plugs used with a type of plastic covered jumper block to short two pins together in place of using a switch. \\
 {{:glossary:header.gif}} {{:glossary:header.gif}}
  
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-Waste heat is produced in transistors due to the current flowing through them. Heat sinks are needed for power transistors because they pass large currents. If you find that transistor is becoming too hot to touch it certainly needs a heat sink! The heat sink helps to dissipate (removethe heat by transferring it to the surrounding air.\\+Waste heat can be produced in semiconductor devices due to the current flowing through them. You will typically see these mounted on power transistors and voltage regulator devices (like LM7805 voltage regulators) providing much greater surface area for the heat to dissipate (transfer) to the surrounding air. They are generally made of aluminum and often have fins. In some high power applications it may be necessary to use a fan to blow air across the head sink to keep the semiconductor device cool. \\
 {{:glossary:heatsink.gif}}\\ {{:glossary:heatsink.gif}}\\
 [[http://www.kpsec.freeuk.com/components/heatsink.htm|http://www.kpsec.freeuk.com/components/heatsink.htm]] [[http://www.kpsec.freeuk.com/components/heatsink.htm|http://www.kpsec.freeuk.com/components/heatsink.htm]]
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 When a hex number is used in a program or written text, it is usually proceeded by some characters to identify which number system you are using.  Consider the number 100. In decimal this is one hundred. In binary this is four. In hex it is two hundred fifty six (0001 0000 0000). If you mean 256 then some programmers and programs would put a letter combination such as '0x', '0h' or # before the number (0x100) or a letter such as H or h after (100h). In the MERG forum you will generally see hexadecimal 100 shown as 0x100.  When a hex number is used in a program or written text, it is usually proceeded by some characters to identify which number system you are using.  Consider the number 100. In decimal this is one hundred. In binary this is four. In hex it is two hundred fifty six (0001 0000 0000). If you mean 256 then some programmers and programs would put a letter combination such as '0x', '0h' or # before the number (0x100) or a letter such as H or h after (100h). In the MERG forum you will generally see hexadecimal 100 shown as 0x100. 
 +ASCII Hex encoding 
 +When sending numeric information over a serial link such as RS232 or RS485 it is not possible to send it as raw binary data as some of the possible 256 byte values have special meaning and are used to control the information flow, for an explanation of this see [[glossary_a#ascii|ASCII]]. Instead each data byte is split into two hexadecimal digits and transmitted as text. For example the value zero, which would be 8 zero bits is transmitted as '00' that is <0x30><0x30>, value 255 which would be 8 one bits becomes 'FF' that is <0x46><0x46>.
  
 ===== High ===== ===== High =====
  
 +There are situations where there are two levels to a signal, which we commonly refer to as High (1) or Low (0). In the case of logic chips, a high (1 condition) is generally a voltage above 2/3 of the supply voltage. In the case of a transistor device, it may be a voltage high enough to turn a transistor on (to make current flow between emitter and collector). This may require several volts on the base. A low is the opposite condition where a smaller voltage, often near ground, is required to produce a low (0 condition) or turn off a transistor.
  
-This what we call greater than the base voltage or ground e.g. so high is 5v ~ 4.4volts above 0 
  
 +===== HO Scale =====
  
-===== H0 =====+Scale and gauge common in America, Asia and Europe but excluding UK. The scale is represented by the ratio 1:87 (3.5mm to the foot). The standard track gauge (width) is 16.5 mm (represents 1/87th of 1435mm).
  
-Scale and gauge common in  America, Asia and Europe but excluding UK. Scale 1:87, gauge 16.5 mm.+===== Hypotrac =====
  
-===== HYPOTRAC =====+This a high voltage track detector system for 2 rail Model railway track , see TB T09/2 merg members only
  
-This a high voltage track detector system for 2 rail Model railway track see TB T9/2 merg members only+ 
 + 
 +===== Hysteresis ===== 
 + 
 +A common characteristic designed into an electronic circuit is called hysteresis. As an example, you may have noticed that most temperature controls for home heating have a couple of degrees of change between off and on. In order to keep the heater from rapidly/constantly cycling on and off, the temperature is allowed to drop a degree or two below the setting before the heater turns on to warm the room back to the setting, then turns off. The heater control is said to have hysteresis. This same process is sometimes used in electronic circuits to prevent circuits from oscillating around single set point. Generally hysteresis is implemented by setting thresholds that a voltage must be above or below before the circuit takes some action. When you encounter an IC logic chip said to be have a "Schmitt Trigger" input, it means that the input voltage must rise above a trigger level, let's say four volts, before the output goes high. A Schmitt Trigger device has hysteresis so the input may need to drop below, let's say, one volt before the output will switch low. In this example, the input voltage can vary between one volt and four volts and the output will not change. 
 + 
 +A similar effect can be seen in ferromagnetic materials acted on by a magnetic field. When a ferromagnetic material is magnetized in one directionit will not relax back to zero magnetization when the imposed magnetizing field is removed. It must be driven back to zero by a field in the opposite direction. Because the material retains a magnetic polarity after it is magnetized in one direction it can be said to have memory. This "memory" is leveraged in making disk drives and magnetic tape drives. 
  
  
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-Hysteresis is well known in ferromagnetic materials. When an external magnetic field is applied to ferromagnetthe ferromagnet absorbs some of the external field. Even when the external field is removedthe magnet will retain some field: it has become magnetized.\\ +The graph of the magnetic field of ferromagnetic materialas it is magnetized through both polaritiesforms a characteristic loop shape 
 +\\ 
 [[wp>Hysteresis|Hysteresis]] [[wp>Hysteresis|Hysteresis]]
  
  
-The term is also used to refer to one of the display modules often to be seen on the [[exhibition_stand|MERG exhibition stand]]. This is because the track layout on the module resembles the graph of a [[hysteresisloop|hysteresis loop]]. +Within the MERG group, the term is also used to refer to one of the display modules often seen on the [[exhibition_stand|MERG exhibition stand]]. This is because the track layout on the module resembles the graph of a hysteresis loop.
  
glossary/glossary_h.1567710846.txt.gz · Last modified: 2019/09/05 19:14 by tgerbic