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A live failsafe is a backup way to run your lights that you can switch to within a minute when the main console or lighting software freezes. For most small rigs, that means fixtures set to hold their last look when DMX stops, a simple backup DMX controller with a few rescue looks, and a cable swap you have rehearsed.
What your lights do when the console crashes
What the audience sees depends on what fails:
- The console or software freezes but keeps sending data. The lights stay on the last look. You have time, and the audience may not notice anything.
- DMX output stops completely. This happens when a laptop crashes, a USB-DMX interface disconnects, or a hardware controller loses power. Each fixture then falls back to its no-signal setting: hold the last values, go to blackout, or start its built-in auto or sound program.
The second case is the one that leaves a stage dark, or with fixtures running their own programs in the middle of a song. Go through each fixture's menu and set the no-signal behavior to hold, if the fixture offers it. Menu names vary, so look for settings labeled "no DMX", "signal loss", or "DMX fail", and check the manual if you can't find one. Not every budget fixture has this option; note which ones don't so you know what they'll do.
Build the backup path before the show
A backup controller with rescue looks
The simplest failsafe is a second, independent controller set up for the same fixture addresses as your main show. A basic hardware DMX controller such as UKING 192 DMX controller works well for this. It doesn't need your whole show, only a handful of looks you could get through a set with:
- A general wash: front light in warm white at a level that lights faces.
- Two color washes that suit most songs, for example blue with magenta, and amber with red.
- Moving heads parked on the stage in open white or a single color, with no movement.
- A slow color chase for faster songs, if the controller supports chases.
- Blackout.
Leave effects out of the rescue looks. Strobe, fast movement, and prisms are easy to get wrong when you are switching under pressure.
If you run your show from a laptop, a second laptop or tablet with the same software, a copy of the show file, and a spare USB-DMX interface gives you a second option. It keeps your full show but takes longer to bring up than a hardware controller.
How to switch between sources
| Method | How it works | Trade-off |
|---|---|---|
| Re-plug the cable | Pull the DMX line out of the main console and plug it into the backup | Costs nothing and takes seconds, as long as the cable is labeled and within reach |
| A/B DMX switch | A switch box selects which controller feeds the line | Fast and tidy; adds one more box to the signal path |
| DMX merger | Combines both controllers onto one line, often with the highest value winning on each channel | No unplugging, but backup faders must stay at zero during normal running; check how it handles moving head channels |
Power and the show computer
- Run the console or show laptop from a small UPS (battery backup), so a brief power dip doesn't reboot it.
- Turn off automatic updates, sleep, and screen savers on the show laptop before the event.
- On Windows laptops, turn off USB power saving (USB selective suspend) so the system doesn't switch off the DMX interface.
- Plug the USB-DMX interface straight into the laptop with a short cable, not through a hub.
- Close other programs, and turn Wi-Fi off unless the show needs it.
- Don't update software or firmware during show week.
What to do when the console crashes
- Leave the fixture power alone. Power-cycling moving heads sends them through their reset routine, and they sweep around the stage while they home.
- Look at the stage. If the lights are holding, you have time to work. If they went dark or started auto programs, switch to the backup straight away.
- Switch to the backup source and bring up the general wash, or whichever rescue look is closest to the current song.
- Restart the main console or software. On a laptop, make sure the USB interface is detected before you open the show file.
- Load the show and go to the right cue, without the output feeding the rig yet if your setup allows it, for example by working in blind mode.
- Switch back at a natural break: between songs, during applause, or on a blackout. Match the look first so the change isn't obvious.
Rehearse the switch
Run the failsafe at least once during setup or rehearsal. Kill the main source on purpose, switch to the backup, restart, and switch back, timing each step. If the restart takes three minutes, you know the backup has to carry about a song's worth of lighting, so the rescue looks need to work for that long. Write the steps on a card and tape it to the backup controller, especially if volunteers or other operators run the rig.
After the show
Write down what was running when the crash happened: which cue was live, what you had just changed, and whether the computer had been asleep or recently updated. Save the show file as a new version, check that it opens cleanly, and try to reproduce the crash at home before the next show. If it happens again on the same cue or effect, rebuild that cue, or look for a software update and install it outside show week. If a hardware controller keeps freezing, contact the manufacturer's support.
FAQ
What happens to DMX lights when the controller is unplugged?
Each fixture follows its no-signal setting: hold the last look, black out, or run a built-in program. Check and set it in the fixture menu before the show.
Do I need a second console as a backup?
Not a full console. A small DMX controller with a few saved rescue looks covers most small shows.
Can I use sound-active mode as a failsafe?
Only as a last resort, and only if the fixtures support it. Each fixture runs its own program, so the result looks random, and moving heads may point into the audience. A rescue look from a backup controller gives you far more control.
How fast should the switch to the backup be?
Aim for under a minute from noticing the problem to having a usable look on stage. Rehearsing the switch is what makes that realistic.
