DMX Issues And Solutions

Wiring

If you’re experiencing problems with your lighting device, such as flickering or no response, the first thing you should check is the wiring. Many lighting and connectivity issues arise when using incorrect or faulty cables. For example, the cable in use might be an audio cable, could be connected incorrectly, or one of its pins might be damaged.

Use the Right Cables

DMX sends a signal to control lights and other devices according to a specific electrical standard. This signal requires a specific resistance, namely 110 to 120 ohms. If cables with a different electrical standard, like audio cables, are used, the signal can be corrupted. This means the clean signal DMX is trying to send can be distorted.

Such distortion can lead to lights either not responding or flashing in undesirable patterns. It can even damage devices. Therefore, it’s always better to use quality DMX cables with the appropriate electrical specifications.

XLR microphone cables might seem like a solution for DMX in a pinch, but this isn’t ideal. These types of cables do not have the specific electrical properties necessary to properly transmit DMX signals. As a result, the lighting system might not function properly; lights might flicker, tremble, or even damage devices. Therefore, it’s always better and recommended to use quality cables specifically designed for DMX systems.

Test Cables Individually

Yes, many things can cause a cable fault; for instance, it might be wrapped incorrectly or the pins could be loose. There are a few simple tests you can do to check if a cable is intact. For instance, you can test the cable ends using a multimeter or check the signal flow using a testing device. Visually inspecting the cable might also help; you can check for any wear, crimping, or exposed wire. You can also check if the pins are seated tightly by plugging and unplugging both ends of the cable. These simple tests can help you understand if a cable is still functional.

A basic test method is to connect the cable to a fixture you know is already working. If the problem continues when using this cable, you’ll know the cable is faulty and needs to be replaced. Here are the steps to conduct this test:

1. Disconnect the cable from the problematic fixture and from a working fixture.
2. Connect the cable to the ‘DMX OUT’ port of the problematic fixture.
3. Connect the other end to the ‘DMX IN’ port of a working fixture.

If the problem persists with this setup, you’ve identified that the cable is faulty and needs to be replaced.

Another quick and efficient way to test a DMX cable is by using a cable tester. These devices send an electrical current to check the continuity of the cable. If the current flows seamlessly from both ends of the cable, the tester typically lights up or emits a sound signal. This indicates that there’s no issue with the cable. The response from the tester may vary depending on its model.

Fixture

If you’ve confirmed all your cables are working correctly, your next step is to investigate potential issues with the lighting fixtures. The problem might arise from having too many lights connected to a single DMX line, or the fixtures themselves might be faulty. Here are some points to consider when troubleshooting DMX lighting fixtures:

Using a Terminator

Remember that only one terminator is needed for a single DMX line, but having a spare terminator is always beneficial.

The terminator should be a 120-ohm resistor and is connected to the last fixture on the DMX line, i.e., to the DMX OUT. If a terminator isn’t used and the DMX signal doesn’t reach the lighting system completely, the signal can be corrupted, leading to undesirable flickering lights or loss of control. This is especially important for large lighting setups. However, no matter how small your setup is, terminating the DMX signal is always good practice.

Test Fixtures Individually

If a lighting fixture isn’t working correctly, there are several factors to check. First, ensure that the number of fixtures you’re connected to isn’t too high. A single DMX line usually supports up to 32 fixtures, and exceeding this number can corrupt the signal.

To pinpoint the source of the problem, divide your current fixture chain into smaller groups. Then, slowly reintegrate these groups. If the problem resurfaces, you likely have too many fixtures.

In this case, you can use a DMX splitter. DMX splitters isolate the signal and distribute it to multiple outputs. This allows you to use more than 32 fixtures without the signal being corrupted, ensuring everything works correctly.

Power Connection

Many modern lighting fixtures have the ability to daisy chain power to one another. This allows power to transfer from one fixture to the next in a “daisy chain” manner. However, different types of fixtures might draw different amounts of power. For example, lights with many effects might consume more energy than a standard PAR Can light.

Thus, if you’re planning to combine different fixtures, it’s essential to know how much power each one draws. This information is usually provided in the product’s user manual. You should carefully read these manuals to understand how many fixtures can be safely combined.

DMX Addressing and Mode

If a lighting fixture isn’t compatible with your controller or isn’t operating independently, there might be a detail that’s been overlooked: the start address set for the fixture or its operating mode. If the fixture isn’t responding or isn’t controlled as desired, it’s likely set to the wrong start address or is in a different mode, such as pre-set or automatic mode.