GCA76 High current interface

Content → Hardware → GCA

• The GCA modules

Some turnout drives need far more power than a standard interface like MGV77 can supply.
One example is the Peco double coil drive, and another are the Märklin drives 74490 and 7549.
Refer to list below for various turnouts.
With this interface, the internal switch of these turnout drives can be bridged. This will improve the function of it.
Thanks to the options of LocoNet or MERG-CBUS, all you have to do is program the MGV50 / CAN-GC2 with a hardware pulse output. ( see at the bottom of this page )
This will take care that the coil in the drive will only be powered for ca 0.2 seconds.
The power darlington transistors T1..T8 are 10 Amp types.
The unit is electrically isolated from MGV50 / CAN-GC2 by opto-couplers.
The board needs addional power of 16Vac minimum 24 VA.
Not all turnout drives really need that high voltage. Always refer to propriate manual.
An ac power (transfromer) used to supply this interface will rresult in a higher dc voltage to the turnouts.\\
Here is an approx calculation for that:
dc on board = (1,4 x ac_of_trafo) - 1,3
with a 16V ac connected, the dc on board will be 1,4 x 16 - 1,3 = 21,1 Volt.
Please consider that in practice this will be slightly higher when transformer is without load.

A short circuit at one of the outputs the fuse F1 will trip .
It resets itself after problem is solved, or ac power has been shut off.
With complete kits, a 1,8 Amp fuse is included, which will normally trip when more than 3 Amp is absorbed.
This fuse can be changed by higher values, but never more than 3 Amp.

refer to: **Connection interfaces**

The list below is just an indication to help you choosing the right Interface for your turnouts.
Most of these turnout coils are made to be used with ac transformer.
Using them in Digital systeem means that they will be powered by DC, causing a slightly higher current through the coil.
In case of any doubts, always refer to the original manual of your turnouts.
To be more accurate the voltage is indicated which is used for measuring the current.

The GCA76 must be activated with a positive pulse.
That means that there will be 5 volt feed into the input, wich will be shut off shortly after that.
On GCA76 itself , there is no electronic device that will take care for this shut off.
Standard turnout decoders usually (there are exceptions) do not have this facility also.
Shut off is done by software in central units or programs, which will activate the coil, and then inactivate after approx 200 miliSecs.
With an GCA76 connected to GCA50 /CAN-GC2 this can be done more safely by GCA50 / CAN-GC2 hardware itself.
Examples below show how settings could be done.
IMPORTANT:

*It is essential to do the settings of GCA50 / CAN-GC2 first, before connecting switches!
*Always repower GCA50 / CAN-GC2 after programming !
The best way to check if programming is done in the right way, and pulses are working, is using a small 12 volt lamp (from automobile ) to check each output.
Each ouput should only shortly light up on activation.
*IT IS IMPORTANT TO PERFORM THIS TEST BEFORE CONNECTING SWITCH COILS !**

Example of GCA50 settings:
	GCA76 is connected to J5 on GCA50 J6 on GCA50 is used for connection of GCA93 current detector.

Example of .CAN-GC2 settings:
	The first 8 ports are set to control 4 turnouts (8 coils) Adresses of Turnouts in Rocrail to be set to 25,27,29,31 Ports 9-16 are set to be connected with GCA93 current detector (Adress 1-8) GCA76 is connected to J4 on CAN-GC2 GCA93 is connected to J3 on CAN-GC2 Using the test-button will change position of turnout on any toggle.

Output 6 is used to command this turnout.
Please realise that adress 7 is used for the the second coil.

GCA76 is also suitable for switching or functions in your layout, like lighting.
The programming is only slightly different in GCA50 / CAN-GC2, because you need a switch, and not a pulse.
Please consider that total current delivered by all 8 connections together, should not exceed 5 Amp.
Also the fuse should be adapted to this.