Alarm and protection of RS-485 faults
Error alarm and protection of RS-485 interface is effective for
connecting multiple RS-485 devices for improved reliability. UT-2204
provides 4 subordinate ports used to determine quickly the faulty ports
and the connected faulty devices according to fault indicators. If fault
occurs then relay will a ct and normally open contacts will be connected
to the common point, so users can connect alarm bell or alarm light to
the relay output terminal.
Power supply and lightning protection
UT-2204 is powered by an external compact switching power sup ply
of 12V/1A. Other non-regulated voltage supply must not be used. This
may cause product damaged. Each RS-485 port of the UT-2204 has a
lightning protection of 1500W, and it can effectively prevent lightning
and ESD. Port 4 of UT-2204 is the protective earth of surge protection
and it's must be grounded correctly to avoid being not-used to ensure
safe communication.
Application note
The data on Input 1 and Input 2 will be transmitted immediately to
Output por t 1- port 4, and the data on any one port of Output port 1- port 4
will be stored to the data buffer and then forwarded to Input port 1- port 2,
so the time interval of Output port 1- port 4 should not be too short. For
example, if the data input of port 1- port 4 last for 100ms for each channel,
then each channel of port 1- port 4 should input data once for more than
400ms and the input data length should be less than 100 bytes, or data
may be lost.
4
5
Typical UT-2204 4-port RS-485HUB applications
1.
4 RS-485 devices controlling 1-2 devices, in which the 4 devices
on the RS-485 bus can simultaneously control 1-2 devices
RS-485
A
Device
( UT-2204 )
OUTPUT1
OUTPUT2
OUTPUT3
OUTPUT4
3
Relay alarm signal output
SIGNAL OUT
No
Nc
COM
signal output
normally open
normally close
common
NO NC COM
2
Extension of 1-2 RS485 ports of a master to 4 RS-485 ports
RS-485
Master Device 1
( UT-2204 )
Port1
Port2
Port3
Port4
RS-485
INPUT1
INPUT2
OUTUT1
OUTPUT2
OUTPUT3
OUTPUT4
Controlled Device 1
Port1
Port2
Port3
Port4
RS-485
INPUT1
RS-485
INPUT2
RS-485
B
Device
RS-485
D
Device
Controlled Device 2
RS-485
A
Device
RS-485
B
Device
RS-485
C
Device
RS-485
D
Device
Master Device 2