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+====== GCA94 8 Input power efficient current detector, also suitable for high current G and 1 Track. ======
+[[english|{{  rocrail-logo-35.png}}]]
+[[:english|Content]] -> [[:hardware-en|Hardware]] -> [[:hardware-en#interfaces|GCA]]
+  *  [[mgv-overview-en|The GCA modules]]
+ \\
+^^^^By Richard Andrews, Helmut Schäfer and Peter Giling ^^^^
+\\
+===== Description =====
+The current detector [[http://wiki.rocrail.net/doku.php?id=mgv93-en|GCA93]] is a reliable way to creatie feed-back in your layout.\\
+But many railroaders experience the 1,2 Volt loss of power as not appreciable.\\
+And also, the current is limited to the maximum load of the bridge rectifiers on the input side of GCA93.\\
+That will basicly disable the use of GCA93 with G-track or 1-track railroaders.\\
+So we created a better solution.\\
+Richard Andrews had this same thought and has been experimenting with different options by using a current tranformer more or less directly connected to A/D converter.\\
+In that way, without any form of amplification, it is hard to reach the minimal 2,6 Volt, you need to activate an input suitable to be used straight to digital systems.\\
+It was fearly easy to add an amplificator to it, but that also increased the sensitivity to distorsions.\\
+In Germany,  Helmut Schäfer created a different approach, using two transistors of which the first one is in normal conducting state.\\
+This eliminates the sensitivity to distorsion, as always produced by running trains.\\
+[[http://www.digitalzentrale.de]] sells this board in two or four ports.\\
+This superb design of Helmut Schäfer is permitted to be used for the GCA94.\\
+GCA94 is made to accept 8 inputs, and can be used like GCA93, straight to GCA50, CAN-GC2, GCA_PI02 and WIO.\\
+No measureable power loss is the result, and there is no need to protect each input with a multifuse, like on GCA93.\\
+The unit is functional compatible with GCA93, also each input has its own indicator led.\\
+One of the two wires to the rails is feeded through any of the coils, which will mostly be sufficient for any locomotive or illuminated waggons\\
+For more sensitivity, a second or third loop through the coil is possible, which could be necessary when you like to detect also\\
+K resistors, mounted between the two wheels of a waggon.\\
+One other and better way to increase the sensitifity is to feed both rail wires through the coil, **but in opposite directions**.\\
+**Note:**
+This unit is strictly made for ac, because it uses a current transformer.\\
+So any digital system (which is also ac!) AND the good old analog ac Märklin will work.\\
+But using it in an analog dc system, including all scales, will most certainly not function at all.\\
+===== The board, professionally made. =====
+|  {{:gca:gca94_pict03.png?700}}  |
+|  though parts are reasonably small,  \\  it is still a rather simpel unit for do it yourself.  \\  In the GCA-kits these resistors are all 125 mW small metal film types.  |
+===== The hardware =====
+|  {{:gca:gca94v2_sch.pdf|The schematics}}  |
+|  {{:gca:gca94v2_pcb.pdf|Printed circuit with parts positions}}  |
+|  {{:gca:gca94_partslist.pdf|The list of parts}}  |
+\\