DMX "burp"

[Ekij]

The easiest solution is to bring your grand master down to zero, then remove the DMX cable from the rear of the desk before powering down.

 

This should be just as likely to break the packet mid way through. It therefore seems more likely that the problem is noise being transmitted as the power is cut to the port driver chips.

 

I also wouldn't recommend leaving the DMX open with the dimmers powered up. The channels may all be off when you leave but some noise on the line could easily cause the dimmers to accept non-zero values.

 

The Numpty who designed DMX didn't fit any error checking at the end of the packet. That was foolish.

It is also foolish to leave the dimmers powered up without a source telling them what they should be doing.

 

It's equivalent to powering down the sound desk before powering down the power amps.

You just don't do this! (You can get pops and bangs that can destroy speaker cones).

 

If you need to leave the dimmers on, then leave the desk on.

[woody74]

We've experienced this situation quite a lot, but so far have only seen it with Strand dimmers, never ETC or Zero 88. My worst experience was at the old Wimbledon Theatre a couple of years ago where they had EC90 dimmers and it took three or four attempts each night to power off the console without any dimmers popping back on.

 

So it would be interesting to know whether other people who have seen this problem are using specific makes of dimmer, e.g. Strand, or whether it is across all manufacturers. I agree with Peter that it seems to be down to the DMX receiver's handling of incomplete packets, so it could be specific to individual manufacturer's implementation of their DMX input systems. Although I see it with dimmers quite frequently, I've not yet seen anything like this happen to moving lights or LED fixtures. e.g. I've never encountered any random movement of lights or LED cells coming back on when powering down the console.

 

I've also seen LD90 dimmers randomly come on just by unplugging the DMX cable, so I am sure that it isn't console related.

 

It has hapened to me with Rosco IPS dimmers and NSI MPX Dimmers (with an Express passing DMX through an IF-501).

 

-w

[peter]

Just to add to the count, the problems I've seen have been with ADB dimmers...

[Stu]

We get the same thing happening from time to time at Poole, with a ETC Expression 3 running ETC Sensor dimmers, the same randomness of the dimmers which get captured happens as per other posters observations.

 

The way I have got round it is by setting the DMX hold time on the dimmers for 3 minutes, so that if dimmers have been captured then at they'll go out on their own accord after 3 minutes instead of me having to continously reboot the desk.

 

I've been advised to check the screen on the DMX cable running from desk to dimmers, but not had the time to do it yet so unsure if this is affecting it.

 

HTH

Stu