What is RDM and Why Does It Matter to Me?

What is RDM and Why Does It Matter to Me?

If you’ve been working with lighting for a while, you might be aware of the term RDM, or remote device management. 

RDM is a killer way to work with your fixtures that are in the air while you’re on the ground.

I love RDM because it allows me to change critical fixture settings from afar!

Did a stagehand or volunteer address 2 lights to the same address?

Are some or all of your fixtures in the wrong mode?

With RDM, you can change any of these things and more!

Depending on your RDM controller, you either can work with 1 fixture at a time, or make changes to a number of fixtures very quickly.

In the days before RDM, accessing functions and diagnostics of your fixture like the DMX address, control mode, lamp hours, and fan speeds meant you had to be next to the fixture – whether it was on the ground or 200′ up in the air!

Say goodbye to this limitation, all thanks to our friend, RDM!

How RDM Works in Stage Lighting:

RDM, or remote device management, works by sending pulses of data down the DMX line in-between the “normal” DMX commands.

While the DMX protocol originally left pins 4 and 5 of the XLR connector open for “future use”, RDM actually doesn’t use them either!  This is one of the most common misconceptions of RDM.

RDM actually communicates down the same lines as your DMX data (that’s pins 2 + 3, for those playing along at home).

These RDM messages place themselves in the “dead air” between DMX messages to get back to your controller.  On the technical level, RDM messages are only sent when requested by the controller – so it’s not a constant barrage of extra information!

Many consoles and devices allow you to scan for RDM on an as-needed basis, or leave your RDM functionality on full-time, though that can cause some issues (more on that later!).

How YOU Can Use RDM:

To use RDM, you need 2 pieces of the puzzle in order to be successful.

You need an RDM-enabled DMX controller, and you’ll need fixtures that are RDM compatible and compliant.  If you use DMX splitters, these will also need to be RDM-enabled and compliant as well.

At the time of this writing, and probably into the future, older and cheaper fixtures aren’t compatible with RDM.  But more and more join the RDM club every year!

Working with RDM is simple!  Just turn on RDM and do a discovery scan to find your fixtures.  Once this has finished, you can go ahead and check on your fixture’s vital signs or change options.

RDM Controllers

RDM controllers come in 3 primary flavors – handheld devices, consoles, and PC software.  Each has its own primary use, but the underlying technology of RDM is the same.

Handheld Devices:

Handheld DMX testers have been around for years and are great troubleshooting tools for technicians.  They can test your cables, test signal strength and even output basic DMX control.  RDM-enabled handheld devices have even more power!

On the positive side, they are able to quickly and easily identify and modify fixtures.  Some can even fully control fixtures without setting a unique DMX address.

These tools are great for use in the shop or in the field to test and check a few lights at a time.  What these units are not made for is changing or monitoring lots of fixtures at once – it’s just not their intended use!

Some of the most popular handheld controllers are:

City Theatrical DMXCat: This battery-powered tester plugs directly into your DMX light and is controlled via a smartphone app.  It allows you to discover RDM, test individual lights, send out DMX signal and more!  Here’s my full review of the DMXCat – I love this thing!

The Swisson XMT-350 is the most serious RDM and DMX testing tool on the market.  Not only can it discover and set RDM modes and addresses, it can easily set the addresses for many fixtures at once – all you have to do is tell it the order!  Testing cables, finding DMX flickers and more – the XMT-350 can do pretty much anything you need out of a DMX and RDM tester!

Consoles and Console Software:

Having the ability to talk back and change settings on your fixtures from your console is actually really handy.

I remember the first time I did this – I was on a Martin M1 and needed to send a truss with a few Mac Vipers out before I had a chance to power them on or address them.

No worries! Once we had the rig up, I was able to simply identify each light in the RDM screen and then go ahead and set the addresses as needed.  No need to go up in a lift to fix it later!

While every console implements RDM differently, having RDM at the console allows you to easily re-configure your lights and monitor temperatures, lamp hours and error messages.

In an installed rig, this is especially awesome because you don’t have to actually access the fixtures themselves to check their vital signs.

Some consoles that have implemented RDM in their software are:


Grand MA2 and 3

Most Current ETC Consoles

Non-Console Software:

Lastly, we have the non-console software.  These are similar to a handheld tester, but have the benefit of being able to modify a large number of fixtures very quickly.  Of course, you need a PC to access them, so it’s not as portable.

Here are some popular pieces of software that can work with RDM:

DMX Workshop:  This free program from Artistic License allows you to discover your RDM enabled fixtures via Art-Net, change DMX modes and more!  Simply connect your computer to your Art-Net node, and you’ll press “Discover RDM” from the Node list screen.  You’ll then be able to identify and modify any fixtures that you discover!

ENTTEC RDM ControllerThe free “Lite” version of this program allows you to discover and work with RDM via the ENTTEC USB Pro Mk II or DMX USB Pro.  The interface is much easier to use than the DMX workshop program, and the full license allows you to do some advanced monitoring and control changes.

Issues with RDM Systems

At the time of this writing, we are in the midst of RDM becoming accessible to the lighting industry at large.  But the rollout is still happening, and there are a few common issues you may run into as you begin to work with RDM.

Non-Compliant Fixtures

We’ve already discussed how not all fixtures are RDM compliant, but it’s important to know that some non-compliant fixtures will flicker, strobe or turn on to full when RDM is coming down the line.

This means that you may not be able to keep RDM monitoring on full time if your lighting rig isn’t comprised of all RDM-compliant fixtures.

DMX Splitters

It’s also really important that you upgrade all of your DMX splitters to RDM-compliant ones – if not, the RDM data simply will not get passed through back to your controller!

Thankfully, brands like ENTTEC, Elation, and Doug Fleenor Design have come into the market already with cost-effective RDM splitters.

RDM is changing the way we manage and monitor our lighting rigs for the better!  No longer do you need to actually access your lights to check vital signs and make simple control changes.

The future lies with those who equip themselves with the tools to manage their lighting rig the easy way – RDM!

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