Driver output lines
The xx03DVR Board can be configured so that
all 40 lines are relay driver outputs or the first 8 or
16 digital I/O lines can be connected directly to
the Parallel Interface board and used as standard
TTL I/O lines. Rocker switches and jumpers on the
xx03DVR Board bypass the relay drivers on bytes 1
and 2 and connect the terminal strip signals directly
to the interface board.
The configuration choices are:
TTL I/O
Relay Driver Outputs
0
40
8
32
16
24
The driver operation is shown in the partial sche-
matic in Figure 2. A high input to the driver circuit
causes it to pull the output to ground and turn the
relay or other device on. A low input turns the driver
off. The external load pulls the signal high. The
xx03DVR does not supply any high side voltage.
When the drivers are bypassed, the output lines are
connected directly to the Parallel Interface Board's
high current TTL lines. The bypassed lines can be
used as inputs or outputs just as it they were directly
connected to the Parallel Interface Board connector.
The TTL lines do supply a small amount of current
from the 5 volt bus and have 33 kohm pullup resi-
tors that pull the lines high to sense open contacts
and lines.
xx03DVR Board Description
The xx03DVR Board terminal strip connections
are identified by bytes and bit, so they easily relate
to the signals on the companion Interface Board.
Standard bit commands like ROUTe:CLOSe or
ROUTe:OPEN can then be used to operate the relay
drivers. Set the Output polarity to high true for the
relay driver signals.
An External Reset input can be used to reset the
Interface board.
Built-in Power Supply
The xx03DVR can be powered from the same
power supply that drives the external relays. The
relay power is used as the return for the drivers'
internal anti-backlash diodes and to power
the Parallel Interface Board. The user should
still use relays with built-in anti-backlash
diodes to minimize RFI. The xx03DVR contains
a small switching regulator that converts 4 VA of
relay power into 5 Vdc to power the companion digital
board,. This eliminates the need for a separate 5 volt
power supply.
Digital signals identified
by byte and by bit
Relay
power
input
Switches connect terminals to board input lines
5 volt power supply
Mating connector for
the interface board.
xx03DVR Board Top View (P/N 115490)
Relay
Power
Supply
+
-
V+
V Return
xx03DVR Board
External Relay Connections
Output
Diode
Relay
Coil
+
-
Off
On
Byte 3, Bit 0
Byte 1, Bit 0
Figure 2 Partial xx03DVR Board Schematic
xx03DVR: Description
