When the lights start to flicker and you seem to have lost control of a DMX lighting fixture or in some cases numerous fixtures, it may be time to get a DMX splitter amp and run a few new direct lines. In a single DMX chain, you can connect up to 32 devices (fixtures). This limitation comes from the electrical characteristics of the DMX512 protocol. A DMX amp splitter, also known as a DMX splitter, is a device used in DMX lighting systems to distribute and amplify DMX signals. DMX (Digital Multiplex) is a communication protocol widely used to control stage lighting and effects. This is an item that has many different things that could affect your lighting system. Let’s lay out a few things we should understand before you start running new cable.
Factors Influencing the Fixture Limit
What is an RS-485 electrical load? Well it refers to the amount of electrical burden devices place on a communication network using the RS-485 standard, which DMX512 is based on. In practical terms, it represents the amount of signal power consumed by each device connected to the DMX chain. Each fixture connected to the DMX chain adds an electrical load. The DMX standard allows for up to 32 loads per chain to maintain signal integrity. If you use a DMX splitter, you can extend the total number of devices by creating multiple branches, each capable of supporting up to 32 devices. While the chain can support 32 devices, cable length also affects performance. The maximum recommended cable length for a single chain is approximately 300 meters (984 feet). Beyond this, signal degradation may occur, and using a splitter or repeater is advisable.
Why Electrical Load Matters
Signal Integrity:
- RS-485 transmits data over long distances and through multiple devices. As more devices are added, the electrical load increases, potentially weakening the signal.
- Exceeding 32 devices without a splitter or repeater can cause signal distortion or loss, leading to unreliable fixture control.
Driver Capability:
- The DMX controller’s driver chip is designed to handle the combined load of all connected devices. If too many devices are connected, the driver may fail to drive the signal properly.
Channel Allocation
Lighting channel allocation refers to how control channels are assigned to individual fixtures or devices in a DMX lighting system. Each channel represents a specific controllable function of a fixture, such as intensity, color, or movement. Proper channel allocation ensures that the DMX controller can send the correct instructions to each fixture.
- Each DMX universe has 512 channels.
- The number of fixtures in a chain also depends on how many channels each fixture uses. For example:
- A fixture that uses 1 channel (e.g., a simple dimmer) allows for up to 512 fixtures in a universe.
- A moving head with 30 channels would allow for only 512 ÷ 30 ≈ 17 fixtures in a universe.
If all fixtures in a chain use fewer than 512 channels combined, you’re limited by the physical load of 32 fixtures. If their combined channels exceed 512, you’ll need to split into a second DMX universe.
Practical Tips
Use DMX Terminators: To prevent signal reflection, always terminate the end of the DMX chain with a DMX terminator.
Check Fixture Specifications: Some fixtures draw more electrical load than others, reducing the maximum number of devices.
Plan Universes Thoughtfully: If you need more than 512 channels or 32 devices, consider adding a DMX splitter or a second universe using a controller with multiple DMX outputs.
In summary, while the physical limit per chain is 32 devices, your total fixture count also depends on the channel requirements and universe capacity.
What is a DMX Amp Splitter?
A DMX amp splitter, also known as a DMX splitter, is a device used in DMX lighting systems to distribute and amplify DMX signals. DMX (Digital Multiplex) is a communication protocol widely used to control stage lighting and effects. A DMX splitter takes a single DMX input signal and divides it into multiple identical outputs. Each output can then connect to different chains of DMX devices (fixtures). The splitter also amplifies the signal, ensuring that it remains strong and reliable across longer cable runs or multiple devices. Most DMX splitters provide electrical isolation between outputs to protect connected devices from issues like voltage spikes or ground loops.
When Should You Use a DMX Amp Splitter?
Multiple DMX Chains: Use a splitter if you need to connect multiple DMX device chains to a single DMX controller, especially if the devices are spread out in different areas.
Long Cable Runs: DMX signal degradation can occur over long cable runs (typically beyond 300 feet/90 meters). A splitter helps by amplifying the signal to maintain its integrity.
Avoiding Daisy-Chaining Limitations: DMX allows for a maximum of 32 devices on a single chain. If you exceed this number, a splitter can help distribute the signal to additional chains.
Electrical Isolation: When devices are powered by different sources or located in areas with potential grounding issues, a splitter with isolated outputs can prevent interference and damage.
Complex Lighting Setups: For productions with multiple zones (e.g., stage, house, backdrop lighting), using a splitter makes it easier to organize and troubleshoot DMX lines.
Use in a House of Worship
For your setup, you might use a DMX splitter to:
- Separate DMX signals for stage lights, accent lights, and effects lighting.
- Ensure reliable performance during holy season sermons or special events.
- Avoid signal loss if your DMX cables are long or if you’re controlling a large number of fixtures.
Tips for Using a DMX Splitter
- Choose the Right Type: Some splitters have 3-pin or 5-pin XLR connectors, so pick one that matches your system.
- Plan Your DMX Universe: Ensure the DMX splitter fits into your system’s universe (512 channels per universe).
- Maintain Termination: Always terminate the end of each DMX chain with a DMX terminator to prevent signal reflections.
The DMX protocol limits this to 32 devices to preserve reliable signal transmission. By using splitters, low-load devices, or multiple DMX universes, you can expand your lighting system beyond this limit while maintaining performance. Proper channel allocation ensures your DMX lighting setup is organized, efficient, and free from control conflicts. If you’re designing a lighting plot for your house of worship, a DMX splitter can help ensure smooth and reliable operation, especially for complex setups.
