BEI Sensors SwiftComm® Real-Time Wireless Encoder Interface - Manual (Page 6)

Most troubleshooting can be accomplished by observing the
state of SwiftComm’s front panel lighted indicators. Following is
a description of the indicator lights and how to utilize them for
troubleshooting:
POWER: This indicator will turn on (green), if power between 5 and
28 VDC is being provided to the module. If this indicator is off,
check the power supply connections.
A, B, Z: These indicators turn on and off as the encoder’s
quadrature signals change state. While slowly turning the encoder,
observe if the A, B and Z indicators toggle on and off in a pattern.
If these indicators don’t respond, check the wiring to the encoder.
A differential encoder signal is required as an input to the module.
LINK: If a SwiftComm transmitter and receiver with the same
security code establishes radio contact with each other, then the
LINK indicator will turn on (green). The LINK indicator will turn off
if continuous radio contact is lost for more than 0.13 seconds
(about 200 packets). The B.I.T output follows the state of the LINK
indicator. Generally, the LINK indicator turns off for three reasons.
1. The RF signal is too weak. This can happen if the radios are too
far apart, or there is some obstruction, such as a building, between
the radios. Try reorienting the radios to avoid obstructions and/or
locating them closer together. Orient the antennas so they are both
vertical or horizontal. In a factory setting, Swiftcomm can typically
transmit reliably up to approximately 300 feet. In an outdoor setting,
that distance can increase to 1,000 feet. Contact the factory to
discuss your specific application environment.
2. The antenna is broken or not attached correctly. The antenna
should be securely tightened to the RF connector on both
SwiftComm modules. Also, inspect the coax wire inside the swivel
base of the antenna to make sure it is not frayed or broken.
3. A source of RF interference exists. Turn off different equipment
in the vicinity to see if the interference decreases, such as
Programmable Logic Controllers (PLC) and variable frequency
drives (VFD). If interference subsides when equipment is turned off,
try moving the source of interference or the SwiftComm modules to
another location. Also check that equipment covers and doors are
secured and the equipment is properly grounded to earth ground.
STATUS: Every 600 uS, the Transmitter sends a packet to the
Receiver with the current encoder data. The STATUS indicator
“flashes” each time an acknowledgment packet is lost. The more
packets lost, the more the STATUS indicator flashes. This makes
the STATUS indicator a good measure of signal quality. Normally
you would see about 1 or 2 flashes per second. This indicates
over a 99% packet success rate. This feature can be used during
initial set-up to optimize the location of the antennas, investigate
intervening obstructions and minimizing sources of interference.
SwiftComm radios are paired in a point-to-point configuration.
Encoder data is sent from the Transmitter module to the Receiver
module, where the data is passed on to the user’s equipment.
Because of this architecture, only one Transmitter and one Receiver
can share the same security code. Over 500 billion unique security codes are available, assuring no address will ever be repeated.
Additionally, all radio pairs are programmed with their security
code at the factory and are not publicly available, which provides
enhanced security of each pair.
Data security was highly considered in the design of the SwiftComm
architecture. SwiftComm deploys three layers of protection to the data.
1. The radios use a pseudo-random adaptive frequency hopping
sequence, changing frequency every 600 uS. This random hopping
helps prevent unauthorized monitoring of the data stream.
2. The data sequence being transmitted between the SwiftComm
radios is proprietary, unlike common radio protocols such as Wi-Fi,
Zigbee or BlueTooth. These publicly known protocols are susceptible
to outside monitoring. SwiftComm’s protocol further enhances the
security of the data while being transmitted wirelessly.
3. SwiftComm uses a 40-bit encryption algorithm for an additional
layer of data protection from external monitoring.
I need a continuous, reliable encoder signal. What
happens if the wireless signal is interrupted and
loses packets of data?
SwiftComm was designed specifically for critical motion control
applications. Its use of an Adaptive Frequency Hopping Protocol
(AFH) helps avoid data interruptions due to frequency interference.
If a particular radio channel encounters interference, SwiftComm
seamlessly hops to another open channel. This technology
decreases the susceptibility to interference, increasing overall
reliability.
Of course, in the real world, signal interference cannot be avoided
in all cases. Because of this, SwiftComm uses patent pending
technology that can overcome data loss due to link interruption.
Internally and transparent to the user, SwiftComm keeps track of
the encoder’s output signal. If SwiftComm encounters packet loss
from temporary link interruption, it fills in the encoder’s output
information based on the historical data trend. It then processes
this information in place of the lost packet. When a valid packet of
information is received, SwiftComm determines any accumulated
error and corrects the quadrature signal to the controller. So even
in environments where occasional packets are lost, SwiftComm will
transmit a seamless stream of data to the control system.
I’m concerned with the security of my data being
transmitted wirelessly. Will SwiftComm protect my
data?
Yes. SwiftComm provides a very secure system for your data to
travel wirelessly. The transmitter and receiver each have a 40-bit
hard coded security code. These codes are programmed at the
factory and give the system a range of over 500 billion possible
unique codes. BEI has developed its own proprietary protocol for
SwiftComm, which is not available to the public. Additionally, the
data is transmitted with a high-level encryption algorithm and
pseudo-random frequency hopping. This provides additional levels
of data security to assure that your data is protected.
What type of encoder can SwiftComm interface with?
SwiftComm can interface with any quadrature incremental or SSI
absolute encoder with differential outputs.
I have an application using a high-speed encod-
er. What kind of latency will I experience with
SwiftComm?
It is critical in any motion control applications to have minimum
lag time in signal transmission. Delays in data to the controller can
cause major problems. SwiftComm is one of the fastest wireless
sensor interfaces available. Data is relayed between the transmitter
and receiver every 600 microseconds (µs). Because SwiftComm
is a point-to-point configuration, there is little inherent latency,
typically about 1mS.
I have an outdoor application and my encoder
cables continually need replacement due to this
harsh environment. Is SwiftComm an option for me?
Absolutely. The SwiftComm transmitter and receiver are both
encased in NEMA 4 cast aluminum enclosures. They are also
powder coated with a gasketed cover. This gives them excellent
protection from windblown dust and rain, splashing water and the
formation of ice on the enclosures.
What is the maximum distance I can transmit my
encoder data wirelessly with SwiftComm?
Like all wireless systems, the maximum transmission distance
depends on the environment where the transmitter and receiver are
being installed. On a factory floor, where there is high electrical noise
and metal obstructions, we typically see reliable communications
up to 300 feet. Outdoors, with line-of-sight and relatively few
sources of interference, this increases to over 1,000 feet.
Can multiple SwiftComm pairs operate in the same
area without interfering with each other?
Yes. Each pair shares a unique security code which ensures they
will not interfere with other SwiftComm pairs in the area. These
codes are programmed at the factory and give the system a range
of over 500 billion possible unique codes. Additionally, SwiftComm
utilizes Adaptive Frequency Hopping (AFH) protocol. If a radio band
is being used by one SwiftComm pair, the other SwiftComm pair
seamlessly hops to another open channel. This helps avoid data
interruptions due to frequency interference.
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