8
2.7 Using the RS-485 Port Connector (J8)
This connector provides RS-485 compatible signals from
the internal master microprocessor. Using jumpers on
the headers supplied near the connector (J12), 120 ohm
termination resistors can be connected and the system can
be connected for either two-wire or four-wire operation
(half or full duplex). To connect the termination resistors,
install jumpers on J12 in the direction shown by the white
bars printed above the connector.
If the jumpers are removed no termination of the RS-485
bus is in effect. Usually, these jumpers must be in position
for proper operation of the bus.
J10 contains the two-wire/four-wire jumper. If the jumper is
set in W2 place, the circuit is set up for two-wire operation. If
the jumper is set in W4 place, the circuit is set up for four-wire
operation. Selection of jumper settings must be determined
by the customer’s system. The jumpers are supplied as
standard and are installed as shown at the factory. Be sure
to set the jumpers properly for your system.
RS-485 Pinout
Following is the pinout for J8, the RS-485 communications
connector.
1 A
2 B
3 Z
4 Y
When connected in two-wire mode, the bus wires may be
connected to pins 1 & 2. Also note that when in two-wire mode,
one termination resistor jumper should be removed to prevent
the termination from being too low in value. It may be stored
on the top set of pins on J12. Those pins are not connected.
Please make sure that your connections are properly made. This
connector is a 4-pin terminal block. Mating connectors are not
supplied. The electrical signals supplied by this connector are
TIA/EIA-485A compliant. A good cable should be used to transmit
signals such as Belden 3109A or equivalent.
Communication Parameters:
RS-485 Parameters
Baud Rate
19200
Data Bits
8
Parity
None
Stop Bits
1
Flow Control
None
Modbus Drop I/O
Factory Default = 1
(user adjustable 1 - 247 )
2.8 Using the USB Host Feature (J7)
The dryer controller is equipped with a USB Host port located
at J7 on the control board which allows for the connection
of a USB flash drive. The USB flash drive can be used for
data logging, event history, and installing software updates.
1. USB Data Logging
When a USB flash drive is installed in the controller it will begin
to automatically record key dryer operating parameters:
timestamp, dryer status, service timer, total compressor run
timer, discharge temperature, evaporator inlet temperature,
evaporator outlet temperature, and dryer % load.
These values will be written every 10 seconds to a comma
separated value file stored in the root folder of the USB
flash drive. Each day a new comma separated value file will
be created for storing the samples for that day. Comma
separated value files older than 60 days will be automatically
deleted.
