Automatic Products Showcase 748, Operating Manual

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APi 748 V1.1 406 4.1 P/N 77500001
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Section 4: Troubleshooting
INTRODUCTION
This section contains technical information to
assist in troubleshooting problems that may occur
in the 748. Separate sections cover indicator
lights, power up sequence, out of service
messages, and specific module troubleshooting
along with a discussion on the serial interface
used to tie major system components together.
While working to isolate a specific problem,
please refer to the system block diagram and/or
the system schematic for additional information.
OVERVIEW
The 748 control system consists of one primary
control board and four secondary control boards.
All four secondary control boards are connected
to the primary control board via serial buss.
Primary Controller
748 Primary Control Board
–
ƒ
Stores the machine setup options, sales
data, and prices.
ƒ
Directly controls the delivery doors.
ƒ
Receives door open and latch interlock
signals.
ƒ
Monitors all health processing.
ƒ
Using a serial interface the main controller
also establishes and maintains
communications with all Secondary
Controllers.
Secondary Controllers
Credit Module –
ƒ
Establishes and maintains
communication with any attached credit
devices, i.e. coin mech, bill validator,
debit card reader.
ƒ
Presents a common interface to the
machine controller for credit devices.
Message Center –
ƒ
Displays messages to the customer on a
20-character vacuum fluorescent display.
ƒ
Sends customer/operator key presses to
the machine controller.
Column Price Displays
–
ƒ
Displays shelf prices and other
compartment parameters.
Refrigeration/Turret Module –
ƒ
Performs refrigeration system control.
ƒ
Reads and transfers probe temperatures
to the machine controller.
ƒ
Performs turret motor movement and half
cycle switch monitoring.
The Power Supply –
Consists of a single dual-secondary transformer
supplying 18 and 24 Volts AC to the relay
interface board.
The Relay Interface Board –
The 24 Volts AC is routed to the Credit Module for
bill validator power, also rectified and routed to the
Credit Module as +24 Volts pulsed DC to power
the Credit Module and provides coin return
solenoid power to a coin mech. The 18 Volt AC
secondary is rectified and filtered to p24
Volts DC which is routed to the 748 Machine
controller and the Refrigeration/Turret Module.
The 748 Machine Controller, Credit Module, and
Refrigeration/Turret Module each have their own
low voltage power supply circuits on board.
Serial Communications
The SerialLink is a proprietary communication
interface used in the 748 to tie major component
modules together. The 748 Controller sends
Serial messages to each of the four Serial devices
and then listens for responses. Serial devices
include the Credit Module, the Refrigeration/Turret
Module, the Column Price Displays, and the
Keypad/Display Module (Message Center). Each
Serial device has a unique device address so
when the 748 Controller sends a message on the
buss, only one of the Serial devices will respond.
Serial devices will not transmit a message on the
buss until polled by the 748 Controller.
The Serial hardware interface is based on the EIA
standard RS485 specification. The control buss
consists of one pair of RS485 signals designated
‘A’ and ‘B’. These signals are 5 Volt differential
signals, meaning that whenever ‘A’ is 0 Volts, ‘B’
is +5 Volts, and whenever ‘A’ is +5 Volts, ‘B’ is 0
Volts.
Communications on the Serial buss are
asynchronous half-duplex such that only one
device may transmit at a time. Transmission
characteristics are as follows:
19200 baud, 7 data bits, even parity, 1 stop bit.