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+====== GCA173 Hall-sensor and/or reed-switch converter. ======
+[[english|{{  rocrail-logo-35.png}}]]
+[[english|Content]] -> [[hardware-en|Hardware]] -> [[hardware-en#interfaces|GCA]]
+  *  [[mgv-overview-en|The GCA modules]]
+ \\
+^^^^By Peter Giling ^^^^
+\\
+===== Introduction =====
+Quite a few systems are available now to detect the Loc, passing a certain area.\\
+Most of them require extra construction inside a loc.\\
+Sometimes, it is already available in the decoder, like Lissy or Railcom.\\
+But to receive these messages, it requires quite some expensive hardware.\\
+One other system , Maerklin's MFX is also nice, announcing the train to be on the track, but it does not give \\
+any information about the exact position.\\
+The wheel-counter **[[mgv141-en|GCA141]]** together with Rocrail, is a system that will tell you at least \\
+that a train has entered completely into the block.\\
+But then, placing the IR transmitter and receiver is a very precise job, maybe not easy to fix for everyone.\\
+All the other systems do not give you any info about if the complete train has entered the block, without losing \\
+some wagons or couches on the track.\\
+This of course unless you will build-in Lissy transmitter  or an extra Railcom decoder and/or have the wagon/coach \\
+equipped with some way of drawing current from the rails, where the current detection on the track will pass that information to the computer.\\
+Reed-switches were very popular long before the digital era was emerged.\\
+But due to the very limited possibilities of magnets, and the fact that faster running trains sometimes 'missed' the \\
+reed-switch made the use of it less popular.\\
+Even now, while we have many other ways of sensing the train on the track, a reed-switch might be sensible to use.\\
+But we have a better, and much smaller option now :  Hall-sensors.\\
+These sensors, like the **[[http://www.reichelt.de/Sensoren/TLE-4905L/3/index.html?;ACTION=3;LA=446;ARTICLE=25717;GROUPID=3190|TLE4905L]]** as described here, \\
+are very small items, even usable for N-track, because this sensor only measures 4,2 x 3,3 x 1,5 mm.\\
+It even can be inserted inside the gravel, making it totally invisible.\\
+The other advantage we have now, is the availability of very strong and yet very small Neodynium magnets.\\
+|  {{:mgv:hardware:wendelsteiner_kieswerk_with_magnet.jpg?500}}  |  {{:mgv:hardware:5mm_cube_underneath_n-kipper.jpg?500}}  |  {{:mgv:hardware:tle4905_in_n-track.jpg?500}}  |
+|  An example of a very small 1x4x5 mm magnet under this Fleischmann N-track 781283 Loc  |  A small N-Track kipper with a (not glued !) 5mm cube magnet.  |  A TLE4905 hall-sensor fixed in an N-track testing circuit\\ It can be fixed between the leggers !  |
+|  {{:mgv:hardware:magnets_122.jpg?500}}  |  {{:mgv:hardware:hall_magnet_182.jpg?500}}  | {{:accessories:pict5268.jpg?500}} |
+|  A small example of all different kinds of magnets available  |  A Roco NS24xx HO Loc with a 1 x 4 x 5mm magnet \\ Top middle is CAN-GC2 and \\ right top is GCA173 (prototype) connected to CAN-GC2  |  One  other HO solution example  |
+\\
+This sensor is 3-wire connected and could be connected directly to a CAN-GC2. or GCA50.\\
+But why should we need this extra GCA173 ??\\
+First of all the connection itself, This pc-board makes that much easier.\\
+Than the pull-up ohm either GCA50 , CAN-GC2 or GCA-PI02 is 10K ohm, which should be much lower to have a solid distortion resistance.\\
+Also a capacitor of minimum 47 nF is needed, conform the data-sheet.\\
+CAN-GC2 needs pulses from feed-back with a minimum lengt of 25 mSec. For GCA50 even the minimum is 80 mSec.\\
+The GCA-PI02 needs minimum of 10 mSec.\\
+That makes them practically not suitable for this hall-sensor, or worse, a reed-contact.\\
+To explain that  let us make some approximate calculations. **:** \\
+If we have a distance of 5mm between magnet and hall-sensor, the magnet will activate the sensor for a length of approx. 7mm.\\
+A HO train, running in scale 120 km/h runs in reality 380 mm per second.\\
+If the sensor only 'sees' the magnet for a length of 7 mm, the time the sensor is activated is 7/380 = 0,018 SEC = 18 milliSec.\\
+A pulse like that is bound to fail, because the pulse will be only 1/4 of what we need.\\
+The CAN-GC2 and GCA-PI02 are better (=shorter) but still way too critical.\\
+GCA173 is here to take care for that\\
+It has connectors for 8 sensors, either hall-sensor or reed-switch.\\
+A small and cheap microprocessor on GCA173 checks continuously all 8 inputs, and will react when one or more inputs are going low, to forward this signal to either GCA50 or CAN-GC2.\\
+Even if the input is no more than 2 millisecs, the output will remain high for 150 milliseconds, assuring that the message is passed correctly to your LocoNet or Can-network.\\
+The hall-sensor itself is much faster than that (approx 1 uSec), so the chance that a train will be 'missed', is 0%.\\
+One other extra advantage of using the GCA173 as a buffer, is that we will have enough connections for all eights sensors.\\
+In case of direct connection between CAN-GC2(GCA50) and 8 hall-sensors, you will have to combine all +5V and 0V connections of the sensors together.\\
+ \\
+===== Features =====
+  *  Easy connection of up to eight individual sensors and or reed switches.\\
+  *  Each input will be passed through with a minimum pulse length of 100 mSec.\\
+  *  Low impedance input takes care for high distorsion immunity.\\
+  *  Even for reed-switches , the low input current is exactly right, to keep the reed-switch in good shape.\\
+  *  1 cable connection to GCA50 / CAN-GC2, which also feeds this board with 5 Volt.\\
+  *  Very low power consumption when all inputs are inactive.\\
+  *  Led signal on each individual input to simplify testing.\\
+===== Counting Rolling stock =====
+The big advantage of this system is the fact that you will be able to detect if the train has entered completely into the block.\\
+As you are used from Rocrail, this fabulous program also does have a standard setting for this sensor, called 'Wheel counter'.\\
+Except here we are not counting wheels but Magnets. But the result will be the same.\\
+At least two magnets should be mounted under the train, the last one under the last wagon.\\
+When these magnets have announced themselves on entering the target block, the conclusion is safe to assume that  \\
+nothing is left behind in a tunnel or shadow station, so the computer will proceed with clearing the used route and use it again.\\
+The sensor itself will be programmed as **[[:sensor-int-en#type|'wheel-counter']]** in Rocrail.\\
+Rocrail will automatically use this counter after the first initiation, and take over this info,\\
+If you like, more than one extra  magnet is an option, even different trains with different number of magnets is an option.\\
+With that installed you could even distinguish which train did come in, but that is an option, not yet available in Rocrail. (Is not planned.)\\
+Commuting trains should be equipped with at least two magnets, so sensors will work in both directions,\\
+and make the train stop at the first detected magnet.\\
+\\
+===== One other interesting option with these sensors: =====
+Using Loc-combinations, where one is a s.c. 'dummy-loc', which is not taking any current from the track, this combination might stop too late, where current detection is used and the dummy is in front.\\
+The use of two magnets -one at each front- will solve this problem simple and easy.\\
+ \\
+===== Handling in Rocrail =====
+Rocrail compares the counted wagons from the **From** with the **To** block:
+  * No comparison is done when one or both blocks are reporting zero.
+  * Normal (done by the "enter" sensor) processing in case the **To** blocks reports equal or more than the **From** block.
+  * In case the **To** block reports less then the **From** block the loco is cancelled from auto mode and the **From** block is closed.
+  * After the lost material is connected to the train again, the **From** block can be set to action, and the train can be re-activated to auto mode.
+===== Boards available =====
+A nice double sided board, with through hole metallisation and silkscreen print is available now.\\
+{{:mgv:hardware:gca173_pict01.jpg?600}}\\
+===== Magnets =====
+A large variety of magnets is available from www.phgiling.net:
+^  Type  ^  Size  ^
+|  1  |  Rod 4mm ∅ length 12,5 mm  |
+|  2  |  Rod 4mm ∅ length 10 mm  |
+|  3  |  Rod 3mm ∅ length 8 mm  |
+|  4  |  Rod 3mm ∅ length 6 mm  |
+|  5  |  Disc 5mm ∅ high 3 mm  |
+|  6  |  Cube 5mm  |
+|  7  |  Plate 5 x 4 x 1.5 mm  |
+|  8  |  Plate 5 x 4 x 1 mm  |
+|  9  |  Plate 5 x 2,5 x 1,5 mm  |
+|  10  |  Plate 5 x 1,5 x 1 mm  |
+|  11  |  Plate 10 x 4 x 1 mm  |
+\\
+Magnets are only sold in sets of 8 pcs per size.\\
+===== Correct position of magnets =====
+Magnets have two poles, of which only one will activate the sensor.\\
+Before putting magnets on your rolling stock, please check the correct position.\\
+This can be done by checking with a sensor itself.\\
+Sensors should be with marked (rounded) side facing towards the magnets.\\
+===== Safety precautions =====
+//**These very strong NeoDynium magnets are no toys !!!!!**//\\
+In principle they are safe by itself, but please be careful with these magnets , do not allow children play with it.\\
+There are quite a few safety remarks, downloadable here : {{http://www.supermagnete.de/eng/safety.pdf|Neodyne safety precautions}}
+===== Connection Hall sensor =====
+The connection wires between Hallsensor and GCA173 can be up to 6' or 2 meter.\\
+Please be careful not to feed those wires parallel with rails and rail wires.\\
+A bit of twisting these wires will inprove protection to any distorsion.\\
+If that is inevitable, keep a distance of 4'' (10cm).\\
+Straight angle crossing is no problem.\\
+Below you can download a drawing of hallsensor connection.\\
+{{:mgv:hardware:connection_tle4905.pdf|How to connect TLE4905L hallsensor}}\\
+The #1 leg of the tle4905 connects with #1 connector to the gca173, the "1" inscribed on the psk-connector facilitates the correct installation!
+===== Connection to reed-switch =====
+Allthough GCA173 can work fine with reed-switch as wel, the option for wheel counter is NOT applicable.\\
+This due to the fact the the number of pulses, generated on the passing of a magnet is never the same, and unpredictable.\\
+{{:mgv:hardware:connection_reed-switch.pdf|connection to reed-switch}}\\
+===== Cable to GCA50 / CAN-GC2 / CAN-GC4 =====
+refer to:
+[[PSK-Interface connections-en|**Connection interfaces**]]\\
+===== Connection table of J1 =====
+^  J1 pin#  ^  Function  ^  Remark  ^
+|  1  |  +5V  |  Supply GCA173  |
+|  2  |  0V/GND  |  Supply GCA173  |
+|  3  |  Hall1  | output sensor 1  |
+|  4  |  Hall2  |  output sensor 2  |
+|  5  |  Hall3  |  output sensor 3  |
+|  6  |  Hall4  |  output sensor 4  |
+|  7  |  Hall5  |  output sensor 5  |
+|  8  |  Hall6  |  output sensor 6  |
+|  9  |  Hall7  |  output sensor 7  |
+|  10  |  Hall8  |  output sensor 8  |
+===== Hardware =====
+|{{:mgv:hardware:gca173_sch.pdf|The schematics}}|
+|{{:mgv:hardware:gca173_pcb.pdf|The pcb and parts positions}}|
+|{{:mgv:hardware:gca173_parts.pdf|The partslist}}|
+|{{:mgv:hardware:gca173_gerber.zip|The Gerber files}}|
+^N.B. Self made pc-boards are not supported! ^
+\\
+===== Firmware =====
+{{:gca:gca173_v1_4_firmware.zip}}\\
+This latest 1_4 version is published, because it has a more accurate timing before resetting the output.\\
+Timing is close to 80 mSec.\\
+{{:gca:firmware:gca173_v1_5_firmware.zip}}\\
+Version 1_5 has a better startup sequence. It will send all actual sensor positions\\
+===== Pictures from satisfied customers =====
+|  {{:mgv:hardware:img_0728.png?400}}  |  {{:mgv:hardware:img_0729.png?400}}  |  {{:mgv:hardware:img_0731.png?400}}  |
+|  3 wires connected to sensor \\ middle wire isolated  |  Drill hole 4,5 mm between sleepers  \\  feed sensor through hole \\  bend wires down ( round head sensor at top side ) and fix sensor  |  a first functional test with 5 volt \\ connected from any adapter   |

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