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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...  |
+|{{:mgv:hardware:gca179_proto.jpg?700}}|{{:gca:gca179_pict01.jpg?600}}|
+|{{:gca:gca179_pict02.jpg?700}}|{{:gca:gca179_pict03.jpg?700}}|
+|  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=====
+{{:mgv:hardware:connection_tle4905_to_gca179.png?600}}
+===== Firmware =====
+{{:mgv:hardware:gca179_firmware.zip}}