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[Mike Karseboom]

I have one of these $35 DMX splitters purchased off eBay and have a question with it's operation.






When I connect the output of a DMXKing eDMX1 ART-NET interface to the input of the splitter I can control DMX fixtures as expected from any of the outputs on the splitter.


However, when I attempt the same thing with the splitter driven by the Martin Freekie controller, I cannot seem to get any type of signal out to the fixtures.  That is, whatever state the fixture was in prior to connecting the Freekie, it just stays there as if no DMX signal is present.


If I remove the splitter from the chain, the Freekie will control the fixtures as expected.


I don't really have anything to measure any type of DMX output so cannot do that kind of analysis.  But from what I can tell the Freekie was made in 2004 and complies with DMX512 and the eDMX1 complies with DMX512-A. From what I have been able to research it seems the Freekie has a frame refresh rate of 32 frame/sec and the eDMX1 is at 40 .  I don't know if that makes a difference.


Any ideas why this splitter would work with one controller and not the other?

[Mark Cadwallader]

I have a vague recollection about reading where old Mac fixtures had pin 2 and 3 values reversed (or something like that). If so, might that help explain the issue? Does that jog somebody else's memory?  Mark C.

[Mike Karseboom]

I have a vague recollection about reading where old Mac fixtures had pin 2 and 3 values reversed (or something like that). If so, might that help explain the issue? Does that jog somebody else's memory?  Mark C.

Thank you for the suggestion.  I checked and this controller does have pin 2- and pin 3+.  So I don't think that is the issue. 


Also, the manufacturer has since told me the refresh rate should not be  the problem.

[Jerome Malsack]

Cables ??  are they microphone cables or true DMX. 

Termination is sometimes a problem for the chain.  The device should have a terminator on the input side ?
 the opto coupled 8 outputs would not be where to terminate the supply chain.  Each opto coupled 8 chains should each have a termination. 

Make a short cable with ethernet cable using three wires Orange and orange and white pair and one other.  the single wire should be pin 1 to pin 1 and the other pair of orange 2 to 2 and 3 to 3.  if using mic wires.

[Josh Daws]

my guess is termination....also if the controller is expecting something to come back to it, chances are the splitter is blocking said information...

[Mike Karseboom]

Yes I am using very new factory DMX cables and have swapped them out to eliminate that.


From what I can tell this device is not a true optical isolator.  Instead it is just a splitter / amplifier.  In any event I did not think each output needed to be terminated.  I did terminate the short run to the simple  one fixture setup used for testing.


As to expecting something back, I thought the DMX512 protocol was pretty much one way out from the controller.  The DMXKing ART-NET converter does support E1.20 RDM but I don't think the Freekie nor the splitter support that.  Is there something else the Freekie might be expecting back?


I have opened up this device and the innards are fairly simple.  It also seems cleanly designed and assembled and I cannot detect any loose connections or internal wiring problems.


I was thinking more that perhaps the eDMX1 has a "stronger" output or something that drives the splitter input adequately and maybe the Freekie does not.  This is just grasping though as the Freekie does fine controlling a 10 fixture chain spanning 200' or so of cable.


At this point I am going to exchange the splitter for a replacement unit but I suspect I will have the same problem with the new one. The manufacturer claims they sell a lot of them and have not had customer complaints.  The fact that it seems to work fine with the eDMX1 makes me think there is some other fundamental incompatibility with the Freekie,which is from 2004.
 

[Jerome Malsack]

Take a look here

http://electronics.stackexchange.com/questions/100487/dmx-on-arduino-with-rs485

The splitter does need to be two direction. 

[Jerome Malsack]

You should see the optical isolation on the bottom half. 

The incoming signal needs to have the pass threw and termination.  with the signal sent Y to the terminator and the optical isolation.  The out going should each have the optical isolation to provide isolation between each branch out. 

[Scott Hofmann]

Take a look here

http://electronics.stackexchange.com/questions/100487/dmx-on-arduino-with-rs485

The splitter does need to be two direction.

There is nothing in these schematics that show something "two directional" ie coming back to the splitter. A standard DMX splitter only "outputs" DMX. RDM is a different story but the splitter has to have that capability.

[Jerome Malsack]

Ok yes your correct the pin 2 and pin 3 are not by directional.  Pin 2 is one way and pin 3 is the opposite. 

That should lead you back to the pin 2 and pin 3 swap to test and see result. 

[duane massey]

Over the past 20 years I have occasionally come across "wth" experiences with DMX. Most were eventually solved, but sometimes even the solution didn't make sense. Most of the issues involved cheaper products, but not always. I grew used to hearing the same phrase over and over from the techs at the various manufacturers, "I've never heard of that before".
Swap out the splitter, but don't get your hopes up.

[Jerome Malsack]

When you change the polarity on pins 2 and 3 for the controller you may also need to do the same on the lights.

[Mike Karseboom]

I asked Martin support about this an no response.  But there are a few more details.


I now have a new fixture, the Blizzard Kaptivator RGB laser, that has the same issue.  That is, it works correctly under DMX control when using the DMX King art-net converter with Luminair, but does not work at all with the Freekie.


I have set up a simple 2 fixture daisy chain with the Freekie controller, the Kaptivator, and a simple led wash light.  None of the fixtures respond to DMX control and both seem to perhaps have all channels set at zero since there is no output. 


The order of the devices does not matter.  If the Kaptivator is first in line, no devices work.  If the Kaptivator is second in line, no devices work.  The same result happens with the splitter.


If neither of those devices are in the chain, the Freekie properly controls a variety of 12  fixtures extending over 250 feet of DMX cable.


Any ideas why the Freekie seems to have no output whenever either of those devices is added to the chain?

[Mike Christy]

Im definitely no DMX expert, but this may be something to try... I have one fixture that just would not see DMX until I powered it on first - with the DMX cable unplugged - then after it initialized, plugged the DMX cable in. It was the only way it would see incoming DMX signals.

Maybe the splitter is corrupting the freekie buffer on power up, or something weird like that?

just a thought...

Mike

[Jano Svitok]

If you have RDM version of DMX King device you may try to connect output of the Freekie to DMX King input what will it see.

[Mike Karseboom]

If you have RDM version of DMX King device you may try to connect output of the Freekie to DMX King input what will it see.

A cool idea - use the DMXKing art-net interface and software as a sort of DMX analyzer.  The eDMX1 unit does have RDM and can be set to receive mode.  However, I cannot really see any kind of results coming from the Freekie into the eDMX1.  I have tried just about every combination of software settings but the DMX display grid just stays black (00).  I don't know enough about RDM ( or any of this for that matter) but suspect the device sending data must be RDM enabled.  If you have specific setup instructions I would be glad to try again.


Mike C. - I am pretty sure I have tried different power and dmx connection sequences but will go back and do it specifically.


I did get a replacement DMX splitter of the same type and the results with that one are the same, so I don't think the splitter was defective.  Also, the Kaptivator causes similar (but not exactly the same) problems.


I was hoping there might be some simple DMX rule I was breaking but it appears this is one of those oddball problems that may not be worth the time it takes me to solve it.  I am mainly a sound guy and the lights are a secondary add on.  The Luminair / eDMX1 setup seems to work well with all devices and that is the primary system.  So I am really not down or crippled. 


I try to carry quickly swappable backups or alternate plans for all critical audio components and wanted to apply that approach to the lighting as well.   The Freekie was purchased as a backup that could be quickly swapped into play if the Luminair/eDMX1 controller failed.  This would still be possible if just the Kaptivator is  part of the chain as it can just be quickly bypassed. But if I have the splitter in the mix it would be too hard to re-configure the cables in a timely manner.


I have done a bunch of other test scenarios and the results have been surprising and very hard to interpret.  For example if I put the splitter between two simple DMX PAR fixtures, the Freekie will actually control the one after the splitter, but the one before the splitter is "dead".  It seems to me like this points to some sort of data timing issue and I may have to just accept that the  10+ year old Freekie will not work properly with some of my devices.

[ProSoundWeb Community]