ProtEX-MAX PD8-6210 Explosion-Proof Analog Input Batch Controller
Instruction Manual
30
Switching Inductive Loads
The use of suppressors (snubbers) is strongly
recommended when switching inductive loads to
prevent disrupting the microprocessor’s operation.
The suppressors also prolong the life of the relay
contacts. Suppression can be obtained with
resistor-capacitor (RC) networks assembled by the
user or purchased as complete assemblies. Refer to
the following circuits for RC network assembly and
installation:
Figure 13. AC and DC Loads Protection
Choose R and C as follows:
R: 0.5 to 1
for each volt across the contacts
C: 0.5 to 1 µF for each amp through closed contacts
Notes:
1.
Use capacitors rated for 250 VAC.
2.
RC networks may affect load release time of solenoid
loads. Check to confirm proper operation.
3.
Install the RC network at the controller's relay screw
terminals. An RC network may also be installed across
the load. Experiment for best results.
Use a diode with a reverse breakdown voltage two to three
times the circuit voltage and forward current at least as large
as the load current.
Figure 14. Low Voltage DC Loads Protection
RC Networks Available from
Precision Digital
RC networks are available from Precision Digital and
should be applied to each relay contact switching an
inductive load. Part number:
Note:
Relays are de-rated to 1/14th HP (50 watts) with an
inductive load.
RS-485 Connections
The RS-485 connections are made to a five terminal
connector used for Modbus
®
RTU serial
communications. The RS-485 terminals include
Transmit Data (DO) and (/DO), Receive Data (DI) and
(/DI), and Signal Ground. See
information.
There are three diagnostic LEDs: Transmit Data (TX),
Receive Data (RX) and METER LINK to show when
the controller is transmitting and receiving data from
other devices.
Figure 15. RS-485 Diagnostic LEDs
RS-485 Multi-Drop Connection
When using more than one controller in a multi-drop
mode, each controller must be provided with its own
unique address. The controller address (Slave ID) can
be programmed between 1 and 247. The transmit
delay can be set between 0 and 199 ms. The parity
can be set to even, odd, or none with 1 or 2 stop bits.
To change the controller address:
1. Press and hold the Menu button for three
seconds to access Advanced Features menu of
the controller.
2. Press Up arrow until Serial (
SEriaL
) menu is
displayed and press Enter,
Addres
is displayed.
3. Press Enter to change controller address using
Right and Up arrow buttons. Press Enter to
accept.
4. Press Menu button to exit and return to Run
Mode.
Three-Wire Connection
In order to wire the five pins for use as a three-wire
half-duplex RS-485 connection, it is necessary to
create a jumper connection between DI to DO and /DI
to /DO- as shown below.
Figure 16. Three-Wire RS-485 Connection
C
R
C
R
__ __
DI
DI DO DO
