QUANTUM™ HD UNITY SYSTEM CONTROLLER
MAINTENANCE
090.670-M (APR 2020)
Page 28
Preface
The information that follows in this section can help locate
problems that may occur with Digital Input and Output
circuit boards, and their interaction with the Q5 and Q6
processor board.
The Digital Board is actually a small microprocessor board
and programmed to control discrete outputs, or accept
discrete inputs, from external electrical devices. Each Digi-
tal Board has the capability of 24 independent channels or
I/O (Input/Output). With the Quantum™ HD Unity Control-
ler, most 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.
Communications LEDs
The Q5 and Q6 processor board are in constant communi-
cation with all Digital, and Analog Boards. Each Digital and
Analog board will have a pair of LEDs labeled RX and TX.
These letters represent Receive (RX) and Transmit (TX),
which flash rapidly during normal operation. This indicates
that the Q5 and Q6 processor board are properly commu-
nicating to their respective analog and digital I/O boards.
• See
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 and Q6 processor 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, this can result in lost or
failed communications, the wrong outputs being ener-
gized, or the wrong inputs being received.
Connections to the Q5 and Q6 Processor
Board
The analog and digital boards connect to their respec-
tive Q5 and Q6 processor board through RS-485 serial
communications. The following is a list of the number of
potential digital boards for each section of the control:
• Condenser - 2
• Vessel - 3
• Engine Room - 1
• Evaporator - 20
The digital board harness consists of a 5 VDC positive
(Red), DC Common or Neg. (black), RX/TX Pos. (white with
red stripe) RX/TX Neg. (white with black stripe).
Logic voltage (power) LED
A Power LED is located on the Digital Board. If the Control
Power switch is ON, and voltage is present at the Remote
panel power supply, the LED is illuminated. 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 Digi-
tal 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
+5 V
lead,
and the black (negative) probe end into the
RET
(Return or
Common) lead:
Figure 13: Return lead
+5V
RET
Set the DVM to read DC, and set the proper range. The
voltage reading must read a minimum of +5.1 VDC at the
last digital board on the harness.
A low 5 VDC reading may occur as a result of one of the
following:
• The power supply may need adjustment (see the sec-
tion on power supplies).
• The Power-I/O communications harness has a problem
(a new harness may be needed).
• A problem may exist with one of the I/O boards (Digital
or Analog).
• If the power LED is not lighted, check the cable for
proper connectivity. Note: Each board provides the
necessary connections to feed all signals to the follow-
ing connectors.
The most common symptom that is be exhibited by a low
+5 VDC voltage to the Digital Boards is an alarm message
that reads Digital Board Reset Shutdown.
Active LED
The Digital Board(s) have an Active LED indicator on the
board that blinks when the board’s software is running.
If the Active LED is not blinking, ensure that the EPROM is
installed properly. The EPROM is located in chip slot U8,
next to the power connector.
Digital Inputs
A Digital Input is the portion of the hardware that allows
devices such as limit switches, relay contacts, and level
switches to interface with the Q5 and Q6 processor board.
The software program within the Q5 and Q6 processor
board constantly evaluates the status of these Input chan-
nels to see whether or not they are energized, and how
that status interacts with the configuration of the control
-
ler.
Digital Board
