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gca179-en [2018/11/12 08:56] (current)
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 +====== GCA179 Isolated Hall-sensor and/or reed-switch input unit. ======
 +[[english|{{ ​ rocrail-logo-35.png}}]]
 +[[:​english|Content]] -> [[:​hardware-en|Hardware]] -> [[:​hardware-en#​interfaces|GCA]]
 +  *  [[mgv-overview-en|The GCA modules]] ​
 + \\
 +^^^^By Peter Giling ^^^^
 +===== Description =====
 +The use of Reed-Switches is fairly common in garden railroad environment. \\
 +It is cheap but face a few problems.\\
 +First there is the '​contact dender',​ causing multiple contacts in one switch action. \\
 +Rocrail does not have any problem with that, as long as it is just a simple feed-back. \\
 +But using the switch as a wheel-counter (or magnet counter here) would give some problems.\\ ​
 +And specially this wheel counter is a very nice option, so far hardly anywhere available but in Rocrail it is standard.\\
 +Second there is the fact that the contact given by a passing magnet is a rather short pulse. \\
 +Most units in LocoNet or CANBUS useually need a pulse-length of minimal 50-75 milliSec.\\
 +And the third fact is that reed-switches have a short functional life, when incorrect current is switched, either much too high or far too low.\\
 +The last issue can be improved by switching the correct current as given by the specifications of the reed-switch,​ which might be mostly very hard to find.\\
 +For all three problems, there will be one simple solution.\\
 +At the present moment I am finishing the development of GCA179 buffer board.\\
 +It has 8 isolated inputs, useable for reed-switch and/or hall-sensor. where a for the reed-switch '​healthy'​ current of approx. 50 milliAmp will be possible. \\
 +The hall-sensor does not have any problem with that current.\\
 +The isolated input enables the use of common Railpower wiring for the reed-switches,​ which makes it possible to use any existing wiring.\\
 +This GCA179 has a connection to GCA50 / CAN-GC2 / GCA_PI02 which also provide the 5V supply for the on-board processor.\\
 +This processor will extend a minimal pulse length in each input to a 0.1 Sec pulse for GCA50/​CAN-GC2/​GCA_PI02.\\
 +At the same time, this longer pulse will sufficiently suppress the multi pulses from contact dender of a reed-switch. \\
 +Hall sensors do not provide contact dender at all, in popular expression: one magnet is one pulse.\\
 +===== Specifications =====
 +  *  8 inputs with opto-couplers.
 +  *  minimum pulse length to activate output = 1 mSec.
 +  *  output pulse length standard 100 mSec minimal.
 +  *  separate 12 Volt 200 mA (100 mA for hall-sensors only) needed for sensor circuit
 +  *  two types of connector possible for 8 inputs : RJ10 or 2/3 terminal screw.
 +  *  up to 100 mtr wiring from sensor to GCA179 possible.
 +===== The prototype =====
 +|  A working prototype is already a fact... ​ |  And the final board has already arrived... ​ |
 +|  The complete board with RJ10 sockets \\  for hallsensor connection ​ |  This board shows the option for using 2 Way screw-terminal (hall7 reed switch) ​  ​\\ ​ or 3 way screw-terminal (hall 8 hallsensor) ​ \\  All hallsensor connections have this same option. ​ |
 +|  = = = = **used screwterminals for hall/reed connections are 3,​81mm/​0,​15''​ pitch types** = = = =  ||
 +===== Hardware =====
 +|   ​{{:​gca:​gca179_sch.pdf|The schematics}} ​ |
 +|   ​{{:​gca:​gca179_pcb.pdf|The pc-board and parts positions}} ​ | 
 +|  {{:​gca:​gca179_parts.pdf|Bill of materials}} ​ |
 +|  {{:​mgv:​hardware:​connection_tle4905_to_gca179.pdf|How to connect the sensors}} ​ |
 +===== Connection HallSensor or Reed-Switch to GCA179=====
 +===== Firmware =====
gca179-en.txt ยท Last modified: 2018/11/12 08:56 (external edit)