GCA21 Reverse loop switch for heavy loads (up to 10 Amp).


By Peter Giling

This page is under development.


Bsed on the use of GCA102, which already have been used many times, and still is,
there was a need for something more useful for large current like G-Track or track 1.
Also because of the more and more getting popular use of hall sensors, this unit is provided with connections for only that.
The on-board relays can switch up to 10 Amp, so that would be enough for one train.
The basic idea was to use it together with GCA179 for hall sensors,\ but the plan is going
to change to the option of having connections directly for hall sensors.
Additionally it is possible to use GCA194 current detector to connect to this unit.
Four hall sensors are needed, one sensor at each side of the railcut, and that at both sides of the loop itself.
These pairs of halls ensors could be connected parallel, making less wiring necessary.
The input is made in a way that longer lines are possible, and unlike GCA102, the unit does not
provide extra sensor inputs for use as feed-back for blocks.
This is mainly because the complete unit is powered by the digital rail power itself.
Hall sensors are able to work with max 18 Volts, so an extra regulator IC3 was needed to achieve 12Volt for the free hall sensor circuit.
Because it is important to maintain the position of the relays, (on should always be ON),
the processor stored the last position in eeprom, so when rail power is shortly OFF and comes back ON , the correct situation of relays will reassured.
Instead of using the railpower, it also possible to supply with a 24 V dc (+/- 100 mA).
In that case, do NOT assemble the bridge rectifier B1.


Schematic plan
The pc-board with parts positions

This is just a preview, objects are liable to changes!

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