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GCA173 infrared opto-gate for wheel-counting with GCA173.


By Peter Giling


The board GCA173 can be used as rather simple real wheelcounter.
This wheel counter option was already available in the sensor properties in Rocrail
but besides the not very popular GCA141, it is hardly used and raher difficult to install.
But I must confess, that it worked perfect on my HO demo unit.!
The use of a very small opto-gate of Sharp, type GP1S097HCZF makes this new idea a nice feature.
The slot opening is just enough to match the size of the HO and N wheel flanges.
Because the input from the opto-gate is reversed in comparison with a hall sensor, this sesnor baord has an
additional FET transistor to correct that.
At the same time, this correction avoids a lot of current consumption, and the GCA173 does require any changes.

This board is to be connected to the hall sensor connectors.
The sensor itself should be mounted at the bottom of the pc-board, opposite of
the other parts.
The three connection points are to solder wires to connect them to the Hall sensor connectors of GCA173,
or even a small PSS 254/3W connector could be used, In that situation there probably shoul be made some space in
bas underlay under the rails.

Connections to GCA173 remark
These connections match the way hall sensors are connected
1 +5 Volt = square pad
2 0V
3 S signal

Since most LocoNet, CAN, RocNet and WIO- units have some restrictions regarding the minimum length of a pulse,
this wheel counter is not suitable for high speeds, when connected directly.
To make it compatable all over, the minimum pulse length, send out from GCA173, is set to 80 msec.
This restriction mainly also has to do with the distance between two following wheels.
Different systems will be tested about the limit of speeds.
But there is one other future option in the firmware.
It will enable to have the GCA173 count all incoming pulses(wheels) end send out that info
as a 80 mSec pulse train.
This assures that no wheel is missed even in higher speeds and/or shorter distance between the wheels.
GCA173 firmware, up until now, will be able to use on speeds below ca 20 mm/sec.

For higher speeds, firmware GCA173_wheel_counter version >1 is recommanded.
Then, there will be an internal counter separately for each of the 8 ports, to count, and count down after transmitting.
Rocrail is perfectly made for that, and addionally there will be special firmware available inide the GCA173
for use this system to control railway crossing.
A second sensor, directly situated after the railway crossing, will open up the gates and shut off warning lights
after the last wheel has passed.
Gates can be motored by small servo motors, which can be commanded in your LocoNet, WIO, CAN and/or RocNet modules.

Even if you are allowing your enthiousistic kids to run train manually over the trajects, the gates will work the same way!
Big FUN!



The firmware adapted to opto gate real wheel counter firmware will follow shortly

More after pcb production and test.

gca173_wheel_counter-en.txt · Last modified: 2024/05/29 16:48 by phg