Bryson Posted August 23, 2010 Share Posted August 23, 2010 I'm putting together a box of tricks that will control a couple of LED ropelights. I need said box to have a DMX in and out. Do I need to install a "proper" DMX splitter in there, or is there a quicker and dirtier method that you can do, given that one leg of the split will be only about 2" from the input? I vaguely recall that this might be OK...but thought I would consult the general wisdom of TBR. Inside the box, I'm going to have a Doug Fleenor GPI converting DMX to 0-10v, which then controls the PWM LED driver. (All powered by a transformer.) DMX in and out, power in, 2 x LED connector out (see my other thread) - all wrapped up in a lovely box with strategic holes drilled in it. Link to comment Share on other sites More sharing options...
smalljoshua Posted August 23, 2010 Share Posted August 23, 2010 Just do the passive split, that's exactly how all of the other manufactures do it. Josh Link to comment Share on other sites More sharing options...
JimWebber Posted August 23, 2010 Share Posted August 23, 2010 As SmallJoshua says, if you just keep the internal DMX wiring as short as absolutely possible, and you should be fine! Jim Link to comment Share on other sites More sharing options...
David Duffy Posted August 23, 2010 Share Posted August 23, 2010 Just run the DMX IN connector wiring to the PCB, then back out to DMX OUT connector. The only stub then is the PCB traces on the DF board. Link to comment Share on other sites More sharing options...
Bryson Posted August 23, 2010 Author Share Posted August 23, 2010 Cool - I was 85% sure that was OK, but it's good to check before I mess up the DMX in my venue! Link to comment Share on other sites More sharing options...
dbuckley Posted August 23, 2010 Share Posted August 23, 2010 Just do the passive split, that's exactly how all of the other manufactures do it.Almost all, have a look at the schematic of a cyberlight... Link to comment Share on other sites More sharing options...
Tomo Posted August 24, 2010 Share Posted August 24, 2010 On most devices the stub ends up being around 5-20cm - the limit is something like 50cm, though I don't have the standard to hand. Not quite sure what dbuckley means though - there are 20R resistors on the D+ and D- stubs in a Cyberlight to support the clamping diodes, but it's still just a passive stub.(I've only looked at revs 2.3 and 3.1.5 though, so they might have done something different before or since) Link to comment Share on other sites More sharing options...
dbuckley Posted August 24, 2010 Share Posted August 24, 2010 Not quite sure what dbuckley means though - there are 20R resistors on the D+ and D- stubs in a Cyberlight to support the clamping diodes, but it's still just a passive stub.Maybe I've got the model wrong - anyway, the interface I'm thinking of is a buffered splitter (ie a receiver and a transmitter chip) with relay wraparound bypass for when the power is off. So your DMX512 topology changes depending on the power status of these particular fixtures... Link to comment Share on other sites More sharing options...
DrV Posted August 25, 2010 Share Posted August 25, 2010 Maybe I've got the model wrong - anyway, the interface I'm thinking of is a buffered splitter (ie a receiver and a transmitter chip) with relay wraparound bypass for when the power is off. So your DMX512 topology changes depending on the power status of these particular fixtures... Same applies to a Dataflash strobe and, I imagine, lots of other fixtures Dave Link to comment Share on other sites More sharing options...
Tomo Posted August 25, 2010 Share Posted August 25, 2010 Ah, yes I have seen a few fixtures with built-in repeaters. Never liked the idea much - it can means that a system that works absolutely fine when the power is on, suddenly stops working if the power goes on a key fixture.- Either because the repeater was covering up excessive line load/length etc, or because it has a stuck relay. (If the relay is stuck in 'bypass', it doesn't matter so much as you see that on the ground because the fixture doesn't work. A relay stuck in 'repeater' mode on the other hand...) It also excludes RDM - though I doubt many people care much about that yet! Link to comment Share on other sites More sharing options...
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