Part Datasheet Search > Development Kits > Bourns J.W. Miller > RS-485EVALBOARD2 Datasheet PDF > RS-485EVALBOARD2 Application Note Pages 1/12
RS-485EVALBOARD2Datasheet PDF
Page:
of 12 Go
If the format of the manual is confusing, please download and read the original PDF file.
Handling Transient Threats in RS-485 Systems
TBU-CA085-300-WH
P40-G240-WH
MOV-10D201K
2031-23T-SM-RPLF
CDSOT23-SM712
TISP4015L1BJ
11/11 • e/CPK1146
Today’s process control architectures and closed-loop systems are developed with numerous
serial drops using point-to-point, multi-drop, or multipoint systems. e distances between serial
drops can range from several meters to over a thousand meters. Data transfer protocols such
as TIA/EIA-485, TIA/EIA-232, TIA/EIA-422, eld buses, CAN, Probus, Interbus, and LVDS,
enable communication with various remote devices such as sensors, actuators, or monitors
connected throughout the system. e RS-485 dierential interface is useful in long distance
communications where immunity to commonmode noise is prevalent, typically found in the
process control factory setting. Process control systems must be designed with robust protection
needed during installation (handling) and commissioning (miswiring), with high expectation
of surviving signicant transients (system transients/lightning). is application note describes
circuit protection solutions that can be implemented to meet a variety of transient standards for
RS-485 serial device ports. Bourns® circuit protection evaluation boards have been introduced
to assist the system designer in developing solutions utilizing the Bourns® TBU® High-Speed
Protector (HSP), Metal Oxide Varistor (MOV), Gas Discharge Tube (GDT), and Transient
Voltage Suppression (TVS) diode products.
Introduction to RS-485
As a standard for industrial communications, RS-485 features fast data rates that achieve 35 Mbps
for short distances and 100 kbps over longer distances. It is not unusual to encounter miswiring
and short circuit faults, especially when covering longer distances. Transients and surges also can
be generated by induced energy on the data lines due to environmental conditions or switching of
heavy inductive loads. Any of these issues can degrade the serial port’s data transfer performance.
RS-485 commonly is deployed in building automation, security system controls, and other
industrial communication applications. One common application of RS-485 that illustrates its
sensitivity is an elevator control system. With cables in motion, and large motors and inductors in
proximity, rugged communication systems are required.
RS-485 systems are inherently more robust than many other networks because the signal is
delivered dierentially between two wires, relative to a third reference voltage. e reference
voltage is oen, but not always, the local earth potential. is provides substantial immunity to
common mode noise such as ground noise and induced noise from nearby motors, solenoids
and transformers. e interface uses voltages that are high by communication system standards,
also making it more robust than networks using other protocols. For instance, Ethernet signals
are about 2 V and the popular USB standard communicates at a maximum of 5 V, though much
internal communication in a computer is even lower. RS-485, on the other hand, allows for
common mode voltages from -7 V to +12 V. e voltage drop between distant nodes can be
accommodated without adding expensive equipment along the path.
Part Datasheet PDF Search
72,405,303 Parts Datasheet PDF, Update more than 5,000 PDF files ervery day.