B&B Electronics 485OPB Datasheet
© 2004 by B&B Electronics. All rights reserved.
www.bb-elec.com orders@bb-elec.com support@bb-elec.com
International Office: 707 Dayton Road PO Box 1040 Ottawa, IL 61350 USA 815-433-5100 Fax 433-5104
European Office: Westlink Commercial Park Oranmore Co. Galway Ireland +353 91 792444 Fax +353 91 792445
PRODUCT INFORMATION B&B ELECTRONICS
DECLARATION OF CONFORMITY
Manufacturer’s Name: B&B Electronics Manufacturing Company
Manufacturer’s Address: P.O. Box 1040
707 Dayton Road
Ottawa, IL 61350 USA
Model Numbers: 485OPB
Description: RS-485 Optical Isolator/Repeater
Type: Light industrial ITE equipment
Application of Council Directive: 89/336/EEC
Standards: EN 55022
EN 61000-6-1
EN 61000 (-4-2, -4-3, -4-4, -4-5, -4-6, -4-8, -4-11)
Robert M. Paratore, Director of Engineering
485OPB-1712-1/3
Model: 485OPB
RS-485 to RS-485 Optical
Isolator/Repeater
Description
The 485OPB can be used to optically isolate one piece of RS-485 equipment from the rest of an RS-485 system, or one
local group of RS-485 equipment from another. It can also be used as an RS-485 repeater to expand an existing RS485 system to greater than the 32 node limitation in the RS-485 Standard. A typical setup using the 485OPB as an RS485 repeater is shown in Figure 1.
All data lines as well as power and ground are isolated from one side of the 485OPB to the other. The 485OPB uses
terminal blocks on each side of the device. It supports Transmit Data (A) and (B), Receive Data (A) and (B), Protective
Ground, and Signal Ground.
Connection
The 485OPB can operate in either two-wire half-duplex systems or in four-wire half-duplex or full-duplex systems (see
Figures 2 and 3). It can also operate as a four-wire to two-wire converter. By connecting one side of the 485OPB as a
two-wire device and one side as a four-wire device, equipment meant for a point-to-point RS-422 interface can be
connected directly to an RS-485 two-wire multi-drop system.
Proper operation of any RS-485 system requires the presence of a signal return path. The RS-485 Standard
recommends that a third wire be used for this. For safety, a 100 ohm resistor should be connected between frame
ground and signal ground at every drop point. For the transient suppression of the 485OPB to work properly, the
protective ground (PG) terminal must be tied to a good frame (chassis, green wire, or earth) ground. No wire type or
maximum run length is listed in the RS-485 Standard. However, the RS-422 Standard, which is very similar,
recommends number 24AWG twisted pair telephone cable with a shunt capacitance of 16 picofarads per foot and no
more than 1200 meters (4000) feet of distance.
Operation
When no data is being transmitted through the 485OPB, the receivers are enabled on both sides of the device. As data
is received on one side of the 485OPB, the opposite driver is enabled and the data traffic LED is turned on. When the
485OPB receives the falling edge of the last data bit, it waits one character time to disable the driver. This timeout
period is factory preset for one millisecond to accommodate a baud rate of 9,600 bits per second. The timeout period
can be changed to any value between 0.26 and 4.16 milliseconds by removing the cover and moving the jumpers JP2
and JP4 inside the 485OPB. The available preset jumper settings should accommodate almost all systems, but a
different timeout can be achieved by putting JP2 and JP4 in position E and changing the values of the capacitors C6
and C9 and resistors R17 and R25. Spaces for through-hole replacement of these components are also provided. They
are labeled C15, C16, R26, and R27. The jumper positions for various baud rates, as well as the resistor and capacitor
values for time-out periods beyond this range are given in Table 1. See Figure 4 for timing component locations.
Jumpers JP1 and JP3 determine whether the receivers will be disabled when transmitting (half-duplex) or always
enabled (full-duplex). As a general rule, JP1 and JP3 should be in the half-duplex position for two-wire operation and in
the full-duplex position for four-wire systems. See Figure 4 for the location of jumpers JP1-JP4 on the PC board.
Specifications
Isolation: 2000 volts RMS for 1 min. optical
isolation of data lines and ground.
Surge Suppression: 6.5V working peak voltage, bi-
directional over voltage suppressor.
600W peak power dissipation.
3,000 pF maximum capacitance
Data Rates: Up to 460.8K baud.
Temperature Rating: 0C to +70C
Power Requirements: 9-14V DC @ 60mA (idle state),
170mA (Full-duplex, 62 Ohm load)
Dimensions: 9.7L x 6.1W x 2.5H cm
(3.8 x 2.4 x 1.0 in)
© 2004 by B&B Electronics. All rights reserved.
www.bb-elec.com orders@bb-elec.com support@bb-elec.com
International Office: 707 Dayton Road PO Box 1040 Ottawa, IL 61350 USA 815-433-5100 Fax 433-5104
European Office: Westlink Commercial Park Oranmore Co. Galway Ireland +353 91 792444 Fax +353 91 792445
PRODUCT INFORMATION B&B ELECTRONICS
Figure 4. PC Board Layout - Bottom
Figure 4. PC Board Layout - Top
FIGURE 2. Four-Wire Setup
FIGURE 3. Two-Wire Setup
Table 1. Approximate Timeout Values
Baud
Rate
Time
(ms)
Resistors
R26 & R27
Capacitor
C15 & C16
(mfd)
Jumper
Position
J2 & J4
300
33.3
330K
0.1
E*1
600
16.6
160K
0.1
E*1
1200
8.33
820K
STD (0.01)
E*1
2400
4.16
STD (430K)
STD (0.01)
A
4800
2.08
STD (200K)
STD (0.01)
B
9600
1.04
STD (100K)
STD (0.01)
C
19.2K
0.52
STD (56K)
STD (0.01)
D
38.4 K
0.26
STD (27K)
STD (0.01)
E
57.6K
0.17
39K
STD (0.01)
E*2
115.2K
0.087
11K
STD (0.01)
E*2
230.4K
0.044
4.7K
STD (0.01)
E*2
460.8K
0.022
2.2K
STD (0.01)
E*2
Note: *1 Remove resistors R25 & R17 when installing R26 & R27,
remove C6 & C9 when installing C15 & C16 for 300 or 600 baud.
*2 Leave R25 & R17 in place when installing R26 & R27 values listed.
FIGURE 1. 485OPB As A Two-Wire Repeater
485OPB-1712-2/3
FCC Approved Class A
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