Lightronics RA121 - Manual (Page 7)

Page 7 of 20
RA – 121 RACK MOUNT ARCHITECTURAL DIMMER
Revision 0.93 OWNERS MANUAL 09/26/2011
www.lightronics.com
Lightronics Inc. 509 Central Drive Virginia Beach, VA 23454 Tel 757 486 3588
DMX TERMINATION
A DMX bus should be terminated (only) at the last
receiving device on the chain. This is done by
connecting a 120 ohm, 1/4 watt resistor across the
DMX DATA - and DMX DATA + lines.
A DMX bus should be daisy chained to all its
receiving units. It should NOT be connected in a star
arrangement with multiple "home runs".
SMART REMOTE CONNECTIONS
There are two types of smart remotes (push button and
fader) which can be used with the RA-121. There are
multiple models of each type. They all connect to a
common RS-485 bus which is controlled by a RA-
121. Additional RA-121 dimmers may also be
connected on the same bus. One of them will be set as
a master bus controller by the
UNIT ADDRESS
ASSIGNMENT .
Smart remote signals to the RA-121 are transmitted
over a two twisted pair, shielded, low capacitance
cable. One pair carries the RS-485 signal and the other
provides a low voltage power and common to the
remotes.
A smart remote bus should be daisy chained to all its
receiving units. It should NOT be connected in a star
arrangement with multiple "home runs".
Each smart remote has a 4 pin connector with screw
down terminals to connect to the RS-485 bus. You
must get the exact wiring pinout information for the
remote unit from its owners manual. The connection
at the RA-121 end is made through the rear panel
DB25 connector. Refer to the CONTROL SIGNAL
CONNECTIONS section in this manual for exact
pinout information.
An example of smart remote connections is shown
below.
SMART
REMOTE
SMART
REMOTE
1 Remote Common (Pair 1)
2 Remote Data - (Pair 2)
3 Remote Data + (Pair 2)
4 Remote Voltage + (Pair 1)
1 23 4
SMART
REMOTE
1 23 4 1 2 3 4
Dual Twisted Pair
Shielded Cable
To RA-121
OR
Multiple RA-121's
Common
Voltage +
Data -
Data +
Shield
SMART REMOTES CABLE ARRANGEMENT
SMART REMOTES CONNECTIONS EXAMPLE
CAUTION
REMOVE ALL POWER FROM THE RA-121
BEFORE MAKING OR CHANGING SMART
REMOTE CONNECTIONS.