DMX compatibility problems with SoundLab LED moodbars

[jules]

Hi,

But I have encountered a problem with SoundLab MoodBars.

I have 2 x SoundLab Moodbars and 2 x Zoom Colourbars.
To all intents and purposes these two units look identical.

I can connect the 2 SoundLab units together and they synchronise perfectly over DMX - one as master and one as slave.

Likewise, I can connect the 2 x Zoom units together and they work fine over DMX.

However, if I connect a SoundLab unit to a Zoom unit as master and slave they do not communicate (the DMX light on the unit does not flash).

I have also connected them to a Discolitez on PC via a Velleman USB/DMX box. The Zoom units work fine, but not the SoundLab unit.
It appears to me that the SoundLab units do not conform to the DMX standard (though they do work with each other)??

Does anyone know how I could resolve this?



As background, the setup I have is :
1) I'm using Discolitez to drive the sound activation - by using line input for sound detection.
2) I have built a JavaRunner to do very basic peak detection (in a lose attempt to do beat detection!!).
3) The JavaRunner calls a basic C++ DLL I developed (so that I can use the Win32 API)
4) The C++ DLL performs a SendMessage to a VB application I developed.
5) The VB application generates random sequences and colours and is triggered by the SendMessage from the C++ DLL.
6) The VB application sends DMX signals to the LED colourbars using a Velleman USB/DMX box via the Velleman DLL API.


Maybe not the best way of doing it, but it kind of works!!!

[jules]

Note: I've fixed this by swapping the pins connections round for the SoundLabs - their polarity is different for some reason!

[ben.suffolk]

This is called Hot Swap.

The problem is because the DMX standard defines 5 pin connectors, so when a 3 pin one gets used (for cost generally) it could be wired either way.

In DMX pin 3 is Hot (+) and pin 2 is Cold (-). Many manufacturers carry this across to 3 pin, but some decided to go with the microphone standard which is pin 2 Hot, and pin 3 Cold. Some clever kit is able to automatically figure out which way round it is and adjust itself.

Ben

[Asmyldof]

Hot swap detection, I think it can be done by identifying the break on your input by a delay in valid data and then during that break see if you're framing wrongly due to only high bits or only low bits. Then it's a simple matter of enabling an external hardware inverter through one IO port of the microcontroller you're using, so you can still use your USART for the RS458 stream.

Or something similar, haven't thought of it much, since I do all my wiring myself I don't really have to care about such stuff, but it's interesting none the less.