WIreless DMX weird behaviour

[BobJ]

We have several groups of LEDs, each group fed from a wireless DMX receiver. All worked well until I got called out because all the LED fixtures were not responding to any commands! On inspection a newly placed ADJ COB Canon (on the floor) was found to have had its mode changed to "Slave". Now for the interesting part; It's wireless DMX receiver was pulsing red (rather like the DMX wireless transmitter). And even then the question remains;

If this fixture was in a wrong mode how did it a/ change the receiver to pulse red and more importantly b/ how did that stop ALL the other wireless connected fixtures working?

Finally; when the Canon's mode was set back to DMX the Rx pulsed green (per norm) and all the other LED fixture groups worked perfectly.

A receiver transmitting!!!!!!

Edited August 3, 2019 by BobJ

[timsabre]

If you are talking about those plug in wireless DMX devices, like an extended XLR barrel, they can be transmitter or receiver. If they detect some DMX coming into them, they switch to transmit mode. So your rogue device was probably in stand-alone mode and transmitting an internal light show which was blocking the DMX being sent to the other units.

[Nid]

A receiver transmitting!!!!!!

Exactly. These are receiver/transmitter modules.

 

They are in (wireless) receive mode by default, Unless they receive the DMX data by the wired connection - then they switch to transmit mode.

The flashing red LED indicates transmitting.

If a fixture that is connected to the wireless module outputs DMX (as in Master mode) the module changes to transmit mode.

 

:)

[Stuart91]

Many lower-end LED fixtures will automatically transmit DMX as soon as they are turned on (and will only stop once they start receiving DMX). So with the wireless receivers, what you need to do it turn it on and wait for the indicator LED to start flashing green, before plugging it into the XLR socket on the first light in the chain.

[Don Allen]

When the newly placed ADJ fixture was placed on the ground, was its mode checked ? I have seen old led par fixtures go faulty and change to master mode after being powered up for a while, which caused them to transmit DMX and cause DMX collision on the DMX chain. It can be intermittant, so when rigging older outdoor fixtures on a truss, I prefer to have the fixtures powered in groups of three, so power can be turned off to isolate an old faulty fixture without losing too many lights. If the new ADJ fixture is doing this, get it replaced under the warranty. Lower priced DMX fixtures usually have their DMX in and out terminals wired together inside so need to be in master mode to transmit DMX.

[timsabre]

All DMX fixtures have their in and out terminals wired together, not just cheap ones. That's standard.

[DrV]

All DMX fixtures have their in and out terminals wired together, not just cheap ones. That's standard.

That's a bit sweeping Tim. I'll give you "most" but not "all"!

[timsabre]

That's how rs485 works... Every device is just a "drop" off a single line, there is no "in" and "out". RDM would not work any other way.

 

Even on the units with both 3 pin and 5 pin connectors, they are all just linked together inside.

[indyld]

To be fair, some units have inexplicably separate IN / OUT wiring and headers that are then commoned back at the PCB. :-)

 

Bonus points if you've ever used a fixture with 3 and 5 pin ports as a jumper or splitter. I can hear pearls being clutched on certain Facebook groups as we speak.

Edited August 4, 2019 by indyld

[Brian]

To be fair, some units have inexplicably separate IN / OUT wiring and headers that are then commoned back at the PCB. :-)

 

But that's the proper way to do it. If you common at the connectors, and then run a 'spur' to the PCB, you will increase the risk of reflections. Whether that makes any difference to the signal is a whole different discussion.

[timsabre]

Let's not get into using 3/5 pin fixture sockets as splitters. I constantly have to stop people doing that on events.

[gyro_gearloose]

3/5 sockets on fixtures are very useful for when I’ve ‘borrowed’ a mic cable after running out of long bits of 5 pin DMX cable, but let’s not re-open the question of using mic cable for DMX :D

[timsabre]

The 3pin/5pin fixtures are a great idea, as long as you don't try to use them as splitters. A shame some newer fixtures have gone to 5pin only.

[timmeh2]

The 3pin/5pin fixtures are a great idea, as long as you don't try to use them as splitters. A shame some newer fixtures have gone to 5pin only.

 

Hi

 

I'll admit to doing this when someone forgot to send the right number of DMX links. Very bad Timmy.

 

It does appear that 3-pin sockets are being ditched on some lines. Chauvet appear to be sticking with both 3 and 5 pin for their smaller fixtures, but their larger fixtures are all 5-pin with ethernet for their stuff that supports pixel mapping, which I think will become the norm.

 

Going back on topic, I wouldn't trust those combined jobbies as far as I can throw them, because they have an awful habit of changing modes if they detect even the slightest gap in the DMX stream, so when using wireless, I prefer to use dedicated TX and RX modules.

 

All the best

Timmeh

Edited August 4, 2019 by timmeh2