limitation of dmx512

DMX is a great protocol to run our lights, but it can’t do everything.

One rule, which I mentioned above, is that you can’t have more than 32 devices on 1 DMX cable run.

All devices on a dmx512 link are connected in a daisy chain. the output of one feeds the input of the next. 

A cable failure anywhere on the link can bring the entire system down.

What’s the deal with that?

As the DMX signal moves through your lights, it loses signal strength over time. At some point, it will become too weak to be reliable.

According to the specification, that is at 32 fixtures.

In real life, that number can vary from slightly lower than 32 to much higher, depending on a variety of factors.

We typically won’t go over 16 fixtures,  just to be on the safe side.  Remember: When lights are hung in a position that you require a ladder or lift to troubleshoot a data issue, play it safe and keep your numbers down!

While you can technically run DMX signal for 1800 feet, I’ve found that anything over 500 feet gets a little scary and can get flaky depending on the number of fixtures attached.

The good news is that if you do begin to have signal problems, you can always split and boost your signal to solve them!

DMX also has a limitation to how much data can be sent down a single line. A DMX line is limited to a total of 512 channels, which is also called a universe. Each lighting fixture you have uses a number of DMX channels depending on how many parameters the fixture has

how long can your cable run be? 

The DMX specification states the maximum length is 3,281'—but think about it. We are working in the real world; every connection can degrade the signal. A good working practice is to limit your cable run to 1,000'.

While DMX is an incredibly versatile and reliable technology, the DMX512 standard does not include automatic error checking and correction. That results in several limitations, and DMX is not appropriate control for applications such as pyrotechnics.  

DMX can also be exposed to false triggering of actions, caused by using poor quality cables, electromagnetic interference, static electricity discharges, poor cable termination or simply very long cables.