DMX-Net RDM Mark II
Connection and layout data - REVISED
Power Supply: (Pin 5) Each module is powered by 9 to 30 VDC. (We recommend 24 volts be used.) At 24 volts a fully loaded module draws less than 40mA. As the power supply voltage decreases, the current requirement increases. The power inputs are isolated from the output and frame ground. The power supply must be fully line isolated and the low voltage common should be DC grounded only at the supply.
Power Supply Common: (Pin 2) The power supply common must be a separate conductor that is not connected to the shield except at one point, usually the system power supply.
time you put into thinking about
cabling before you order
material is an investment in your project turning
out well. Many
installations can use one type of cable to carry
both power supply and
the DMX/RDM data. The most commonly used cable
types are 120 ohm
485-style twin pair cable (AWG 22) or CAT5 ethernet
Often a single run of cable will handle the data and
power supply needs
of your system. Example 1 - a system of
32 modules, with
between-module spacing of 8 ft, run on CAT5.
Put a 24 VDC power
supply at the first module, and use the non-data
wires in the CAT5
cable for power supply and ground. Example 2 -
a system of 24
modules, with between-module spacing of 20 ft
between each pair of
modules, can be run on standard 485, 22AWG
cable. Put a 24 VDC
power supply at the first pair of modules, and use
the non-data pair
for power supply and ground.
Many other systems are easily
accommodated, including ones with the
power supply remoted to a control closet/room.
Please contact the
An important parameter when sizing distribution cable is the voltage drop on the power supply return (common) wire. Any drop in the common return appears as common mode voltage on inputs to these modules. EIA485 has inherent common mode voltage of about 2 volts and a positive common mode limit of 12 volts. Ground return drops of greater than 3.5 volts should be avoided. Ground return drops of more than 6 volts are undesirable and could cause mis-operation. Please consult the factory.
The choice of cable type depends on several factors. The simplest wire to install is the two-pair 485 cable. At the worst, two wires will need to be terminated under a single clamp. In other installations, lower line resistance can be had by paralleling conductors in a CAT5 cable. In this case, multiple conductors will need to be terminated to carry the ground and power supply. There are several ways to handle this; please consult the factory. CAT5 cable is well understood by low-voltage datacom installers. Unless the cable is run in metallic conduit, shielded CAT5 is preferred.
Jumper SettingsThere are a number of internal jumpers on the modules. The units are shipped with the default jumpers installed. In most cases the installer only has to properly configure J8 and J9. The modules on either end of an internal network segment (daisy chain) will have them installed; other modules will have them removed. It does not matter whether that module is an input or an output.
The voltage level on pin 6 of the module determines if the tally light is enabled. If the line is high (2.7V to5 V) the front panel tally is disabled.If the pin is grounded (-0.2V to 0.8V) the tally light is enabled. If Pin 6 is left open, the state of the tally light is set by jumper J7.
Goddard Design Co. home page