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+====== GCA125 Interface for turtoise type turnout drives ======
+[[english|{{  rocrail-logo-35.png}}]]
+[[english|Content]] -> [[hardware-en|Hardware]] -> [[hardware-en#interfaces|GCA]]
+  *  [[mgv-overview-en|The GCA modules]]
+ \\
+^^^^By Peter Giling ^^^^
+==== Features and facts ====
+{{  :gca:gca125_pict02.jpg?300}}
+  *  8 individual inputs, commanding 8 individual outputs
+  *  600 mA max load per output.\\
+  *  Max 42 Volt per output.
+  *  Time selection for output duration.
+  *  Outputs are activated one by one for power reduction.
+  *  Processor on board is isolated from the board by opto-couplers
+===== Description =====
+Controlling a LGB 1201, Kato or Fulgurex turnout-drive, in fact also some type of Hoffmann turnout motors, only have one coil or motor, that needs to be controlled by polarity.\\
+Even the Bohler WA2 is very nicely useable with this interface.\\
+The normal driver like GCA77 is not suitable for that.\\
+The complexity of this unit is slightly higher.\\
+For GCA drive-units it is standard, to have an isolation between power for the coils or motors and the used network system by means of optocouplers.\\
+That is also done on this board, but in a bit different way.\\
+The processor runs on 5V from GCA50 / CAN-GC2 or GCA_PI02, and the processor drives two optocouplers to send I2C commands to the I2C expanders.\\
+This unit is able to control 8 turnouts, and need 8 inputs from the GCA50 / CAN-GC2 / GCA_PI02.\\
+It is also possible to use a switch for direct activation without GCA50 / CAN-GC2 / GCA_PI02. \\
+You will need a 5 Vdc to activate the processor, connected to pin1(+) and pin 2(-) of J3.\\
+In that case pin3(=input 1) to pin10(=input8) of J3 are to command the motors.\\
+One other option is to use GCA174 DCC or Motorola function decoder, to drive directly from the central unit.\\
+The software in the PIC16F628 is made in such a way that the processor provides a correct timing for the coil, and switch it off after the chosen time.\\
+This will take care that the turnout coil or motor will not be overheated by too long powering.\\
+The time selection is done with the Dipswitch, and counts for all outputs.\\
+The processor in the circuit needs 11 inputs and 18 outputs, and 3 extra for dip-switch reading. \\
+Instead of these 29 I/O ports, smaller PIC processors have only maximum 16 I/O.\\
+\\
+\\
+===== Old version  =====
+[[GCA125-proto-en|This is the original page for this board, created for a home-made prototype.]]
+ \\
+\\
+===== The hardware files =====
+|  {{:gca:gca125_sch.pdf|The schematics}}  |
+|  {{:gca:gca125_pcb.pdf|The pcb Layout}}  |
+^  N.B. Self made pc-boards are not supported!  ^
+\\
+\\
+===== Cable to MGV50 / CAN-GC2 / GCA_PI02=====
+refer to:
+[[PSK-Interface connections-en|**Connection interfaces**]]
+\\
+===== Using GCA125 without GGCA50/CAN-GC2/GCA_PI02 =====
+It is possible to use the GCA125 as a stand alone unit.\\
+A 5V supply should be feeded to J3 (pin1 +, pin2 -).\\
+Pin 3(=1) to 10(-8) should be switched between +5V and - for position select.\\
+===== Firmware =====
+{{mgv:hardware:mgv125.zip|program files}}
+\\
+\\
+===== Led functions =====
+Green led: is on when no output is activated.\\
+It is off when one of the ouputs is active.\\
+\\
+Red led: will flash when one of the ouputs is active.\\
+If flashes as many times as the binary value of SW1.\\
+Led is off when no output is activated.\\
+\\
+===== Time delay settings =====
+SW1 is used to set the delay time after which the output will be swotched off.
+^ Delay table  ^  ^  ^   ^
+|  Motor activation  \\  in Sec  |  SW1.1  | SW1.2  |  SW1.3  |
+|  0.1   |  Off   |   Off   |   Off   |
+|  0.2   |  Off   |   Off   |   On   |
+|  0.4   |  Off   |   On   |   Off   |
+|  0.8   |  Off   |   On   |   On   |
+|  1.6   |  On   |   Off   |   Off   |
+|  3.2   |  On   |   Off   |   On   |
+|  6.4   |  On   |   On   |   Off   |
+|  12.8   |  On   |   On   |   On   |
+===== Remarks =====
+Inputs, if activated, should remain activated, to keep motor/coil in the chosen position.\\
+GCA50/CAN-GC2/GCA_PI02 ports should be programmed as switch, with C2 NOT checked.\\
+Checking C2 will inverse action.\\
+\\
+===== Induction knowledge =====
+Motors and single coil dirves, also the ones in turtoise engines, are using coils.\\
+And a coil, feeded with a current, will push back a large power surge, when it is switched off.\\
+That behaviour, for example, is used in cars for creating the ingnition spark.\\
+But in modelrailroad, we do not want any sparking, execept the look of the layout of course.\\
+In dc systems. it is rather easy to suppress that spark by connecting a diode straight on the coil,\\
+and connected in such a way that the cathode is at the positive side.\\
+Any electronic system will thank you for that. It saves you a lot of trouble.\\
+These diodes are in GCA125 inside the L293D chip, so we do not have worry about that.....\\
+WRONG!! because in most motor driven tortoise units, and also the turnouts, moved by (single-) coils, there is a limit switch\\
+which will disconnect the motor/coil from the driver (in GCA125 the L293D chip).\\
+This switching off then also disconnects the on-chip diodes from the motor/coil! \\
+This problem, by the way, causes many limit switches in turnout coils to fail after some time, due to the generated spark.\\
+Now, one option is to bridge these switches, because with the available timer on the GCA125, the motor will switch of after a chosen timing.\\
+But if we like to keep the switch in function, we need to find another solution.\\
+And specially on motors and single coil units, that is a problem, because there is no +/-. because they will be reversed for reaching the oppossite position.\\
+So a diode cannot be used here\\.
+The other solution for that is a VDR or varistor.\\
+These VDR's, (useally here something like a 30V type), will short the motor/coil as soon as the voltage exceeds 30V.\\
+So if you have this situation, use a VDR like VDR-0,25 30, directly connected to coil or motor, and your problem is solved.\\