Twelve questions covering cable, topology, fixtures and verification. Answer each one yes, no, or don't know, and be honest about the third. An answer of "no" is a known problem with a known fix. An answer of "don't know" is the one that matters, because an installation with unknowns in it is not a design.
| Your answers | What it means | What to do |
|---|---|---|
| All yes | A good position, and better than most | Confirm the planning figures against your specific project before committing the design |
| Any no | A known problem, which is the good kind | Fix it: change the cable, shorten the run, add a rated splitter, fit the terminator, move a device to its own segment |
| Any don't know | Not a design. It may work, but you have no way to tell in advance | Establish it yourself, or have the design reviewed |
If any question below is unfamiliar, the background is in what changes when DMX runs faster than the standard.
Cable and run length
- Do you know the make and type of every cable on the Overdrive runs, and is all of it DMX-rated 120 ohm shielded twisted pair?
- Do you know the total length of each run, including the leader from the node to the first fixture?
- Is every run comfortably inside the planning figure, with room to spare rather than sitting on the number?
Topology and distribution
- Is every run a single daisy chain, with no stars, T-pieces or Y-splitters anywhere on it?
- Is every spur, tail and drop off the main run shorter than roughly half a metre, including the ones that are not on the drawing?
- Is the far end of every run terminated with 120 ohm?
- Have you confirmed that every splitter, buffer, isolator and patch point on the line is rated for Overdrive rather than for standard DMX?
- Is every receiver on each Overdrive segment Overdrive-capable, with no standard-speed devices sharing the line?
Fixtures
- Do you know how quickly your fixtures' DMX receivers switch, and whether any optical isolation inside them will pass an Overdrive signal?
- Do you know whether your fixtures' thru ports are passive or buffered?
- Has your fixture supplier confirmed, in writing, that the fixtures are suitable for Overdrive?
Verification
- Will the installation be tested at full run length, with the full fixture count, at the temperatures it will actually operate at, for long enough to catch intermittent faults?
If you could not answer questions 9 to 11
Most people cannot, and it is worth saying clearly that this is not a failing on your part.
Those three questions ask about fixture characteristics that no manufacturer publishes, because until recently there was no reason to. If you are using third-party fixtures, the information you would need to answer them honestly may not exist anywhere you can reach. That is a real and widespread gap, not an oversight in your process. Why your fixtures decide whether it works explains it in full.
Turning a don't know into a yes
There are two honest routes.
Establish it yourself. Get whatever answers your suppliers can give, build a representative sample of your worst-case run at full length with the full fixture count, measure the signal partway along the chain as well as at the far end, run it for an extended period across the temperature range it will see in service, and repeat for each fixture type in the design. That is real work. It needs equipment, time, and fixtures on hand before the installation is committed. It is also the only way to turn a don't know into a yes without help, and it is worth being realistic about whether the project has room for it.
Have the design reviewed. If you would rather not carry that risk, send it to us. Tell us the run lengths, the cable you intend to use, the topology and the fixtures, and we will tell you what we can confirm and what we cannot. Where ENTTEC supplies the node, the cable specification and the fixtures, the questions above are already answered and the chain is validated as a system.
Contact ENTTEC about your project
Responsibility
Installation design is the responsibility of the system designer or installer. ENTTEC specifies the operating conditions for Overdrive mode, and those conditions are approximations for planning that must be confirmed against the actual installation. Verifying that a given design meets them, including the behaviour of fixtures ENTTEC did not supply, requires a review of that specific design and cannot be done from a datasheet. Where ENTTEC supplies the node, the cable specification and the fixtures, the chain is validated as a system.