QUANTUM
™
LX EVAPORATOR CONTROL PANEL
MAINTENANCE
090.610-M (MAY 2016)
Page 30
DIGITAL BOARD
INFORMATION
The information that follows in this section can help
locate problems that can occur with Digital Input and
Output circuit boards, and their interaction with the
Q4/Q5 controller.
DIGITAL BOARD DESCRIPTION
The Digital Board is actually a small microprocessor
board and programmed to control discrete outputs, or
accept discrete inputs, from external electrical devices.
Each Digital Board has the capability of 24 independent
channels or I/O (Input/Output). With the Quantum™
LX Evaporator Control, some of these I/O channels are
dedicated as to their function, through the operating
system (software), enabled options and external wiring.
Each channel that is used by the software will have a
module plugged into it. A yellow module indicates that
it is used for Inputs, a black module is used for Outputs.
The standard Quantum™ LX Evaporator Control can
have up to two Digital Boards (depending on options).
COMMUNICATIONS LED'S
The controller is in constant communication with all
Digital (and Analog) Boards. You will notice on each
Digital and Analog board, that there are a pair of LED’s
labeled as RX and TX. These letters represent Receive
(RX) and Transmit (TX). These LED’s should be ashing
at a high rate during normal operation. This indicates
that the Q5 (or Q4) control board, and the Digital Board
that you are looking at, are properly communicating
with each other.
• Reference the JUMPER AND DIPSWITCH
SETTINGS section later in this manual. This
section contains the dipswitch settings for
addressing the Digital I/O Boards. When
these switches are properly set, the Q5 (or
Q4) board is able to serially communicate
with each I/O board and provide control
signals and data exchange. If these switches
are not properly set, the result will be lost or
failed communications, or the wrong outputs
being energized, or the wrong inputs being
received.
CONNECTIONS TO THE QUANTUM™
The Frick
®
Evaporator control system utilizes up to two
Digital, and one Analog Boards. To connect all of these
boards together so that the Q4/Q5 can control them,
they must be interconnected with a wiring harness that
provides all of the necessary D.C. voltage requirements,
as well as the communications capabilities. Upon close
examination of this harness, you will notice that each
of the connectors have two rows of connections. The
wires that are inserted into the positions of one row,
are internally daisy-chained on each I/O board, to
continue the voltages and signals to the adjacent row.
Therefore, any time that a connector is unplugged from
the daisy-chain, these voltages and signals cannot
continue through the daisy-chain to the next board.
Whenever a plug is not to be inserted into a board,
either for service or if not all boards are present, then
a shunting plug (refer to Replacement Parts list) must
be installed onto the open connector.
The Digital Boards only require the +5 Vdc voltage
and the Return (or common) for logic power. The
communications signals (RX & TX) are required by all
boards.
LOGIC VOLTAGE (POWER) LED
Located on the Digital Board is a Power LED. This LED
will be illuminated as long as the Control Power switch
is ON, and the proper voltage is present at the Remote
panel power supply. The power supply generates the
+5 VDC voltage, and passes it on through the Power-
I/O harness. This LED does not indicate however
that the proper voltage is necessarily present at the
board, only that the voltage is enough to energize the
voltage sensing circuitry. If a voltage related problem is
suspected with regard to a Digital Board, the only way
to actually determine this is to read the voltage on a
Digital Voltage Meter (DVM). This may be accomplished
by locating the white power/communications connector
on the board. Notice that the Digital Board has one
of these connectors on both ends of the board. The
associated power/communications harness will only
be plugged into one of these connectors. Take the red
(positive) probe of the DVM and carefully insert the
end into the “+5V” lead, and the black (negative) probe
end into the “RET” (Return or Common) lead, as shown
below:
Set the DVM to read DC, and set the proper range.
The voltage reading must read a minimum of +5.0 Vdc.
The Power-I/O harness will have an associated voltage
drop at each board connection. As an example, if you
are reading the voltage at the rst I/O board in the
daisy-chain, and it reads 4.98 Vdc, you can be assured
that the voltage at the subsequent connections for
the remaining boards will be lower yet. The voltage
will need to be corrected for proper operation of the
system. The cause for a low voltage reading could be:
• The power supply may need adjustment (see
the section on power supplies).
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