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Z31980_00_03
Design and Function
• GAB/2 Backplane (Interface to GAB/2 Board and -24V power Supply) Slave of Main
Board
5.3.2.1 Shim Control
The Shim Control comprises two shim boards, each of which is capable of controlling up
to 12 channels and a H0 coil. The two boards are cascaded and controlled from the
main board CPU via CAN-Bus. Each channel has a 16-bit DAC and can deliver up to
300 mA. The shim board has an ADC with a multiplexer which can measure the current
flowing through each coil for diagnostic purposes. Please refer to the web server
description for details.
The shim currents are fed to the peripheral control board via 4 ribbon cables (2-per
board) where they are converted to the standard BOSS1 Connector.
The 20 shim terms are divided up between two shim boards:
Figure 5.10 Two Shim Boards
The shim control boards are identical in build. The definition as to whether a board is
shim board #1 or #2 is done via a jumper connector which is plugged into ST11. If this
connector is present, it becomes board #2. This is also shown by LED “LD7” which is
then lit.
Since shim board #1 also controls the H0 current, it has a connection to the Lock Board,
where the lock control voltage is generated.
The shim boards receive only 28Vdc from the central 28V PSU and generate all the
other voltages they requires on board.
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