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gca125-nl [2018/11/12 08:56] (current)
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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.\\
 +
 +  ​
 +
  
gca125-nl.txt ยท Last modified: 2018/11/12 08:56 (external edit)