Thread: Help! Issue with Medusa DMX/ GYS Skull and DMX Dimmer Pack

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Ok guys I have run into a couple wierd issues along the way today and have figured them all out. But this last issue I have run into has been really stumped. If I cant get this figured out my last two pnuematic props wont be working work halloween. So here is the deal.

I have 6 DMX wash lights, a Medusa DMX board running a GYS Skull and 1 DMX dimmer pack that will run 3 pneumatic props (Spitter mech, Coffin Lid Riser, and a Skeletal pop-up.

My main routine is my GYS Skull, 6 lights, and the Coffin lid riser. All of these work perfect in the routine. Now I want to create another routine for my skeletal pop-up. When I create the routine in VSA I disable all the other channels. When I run the routine my skeletal pop-up works fine but something wierd happens with the GYS skull off the Medusa board. One or more of the servos (cant tell) move so so position that is out of its bounds and I can hear them binding (not a pleasant sound). So I shut off the board immediately. If I have the board powered off then the routine works fine.

At first I thought it may be something with the cables but when I run my main routine everything works fine. I'm really stumped!!

Anybody have any suggestions?

So, one routine works fine (including skull and one pneumatic). And the other routine, the pneumatics work fine, but the skull moves in an uncontrolled manner?

This sounds like channels might be overlapping. Can you look in VSA and tell me what address the pneumatics are set up as? And also tell me what physical address switches on the Medusa DMX are turned on?

Thanks,
- Hook

That's what I initially thought. But I was messing with it some more and if I just enable the skull/servo channels and create an initial action to just set the servos to its default position than its fine. I just would have thought that if I disable them than it wouldn't even turn it on. I can just use this as a workaround for now since my routine that runs the servos will not have any routines running at the same time. But I'm really confused on what's happening.

Here is my layout:

0-3 - DMX Light 1
4-7 - DMX Light 2
8-11 - DMX Light 3
12-15 - DMX Light 4
16-19 - DMX Light 5
20-23 - DMX Light 6

30 - Starting address for Medusa Board

60 - DMX Relay Pack - Channel 1
61 - DMX Relay Pack - Channel 2
62 - DMX Relay Pack - Channel 3
63 - DMX Relay Pack - Channel 4

I think I know what's happening now. Addressing in DMX is not an explicit part of the protocol, like [address 5] [goto position 25]. Instead, the address is implied, based on how many bytes of data have been sent out since a 'break' in communication. So.... it goes like this... (this is the nominal frame)

____--------________xxxxxxxx-xxxxxxxx-xxxxxxxx-xxxxxxxx....
BRK....MAB..StartCode...CHN1.....CHNL2...CHNL3.... CHNL4......

So, first a 'break' in communication occurs, then there's a 'mark' after break (a bunch of 1's), then a start code, which most of the time is zeros. Following this preamble, comes all the channel data. Each slave device counts the number of bytes going by, and once the right number of bytes have gone by, they know that's their channel data (that's their addresses data)

So, the point here is, that even if you have certain channels 'disabled' in VSA, the DMX bytestream still needs to assign these a value, because they'll be broadcast no matter what, even if they're just acting as 'placeholders'. In this case, since VSA isn't animating, the value is arbitrary, but I'm guessing it's zero - which would correspond to all servos going to one extreme.

I think your workaround is probably the proper way to deal with this. Although I'm betting you don't actually have to even put in a dummy move for these channels. I think as long as you have the channels enabled, and have the proper default value set up on the configuration page, they should go to their center positions on start of the routine.

- Hook

I think my head just exploded after reading that first part :P Been programming all day and still finishing the last routines as we speak. But I get what your saying. For now I'm just using that initial dummy move for now and I will play around with removing it after tomorrow. I'll let you know how it goes.

Thanks for the quick responses!

When I program I only hook up the device that I am working with one at a time. It’s only for show testing and the actual show that I hook them all up.

Sorry for the confusing explanation. I was hobbled by the party I'd just come back from :P

Yeah, so, in short.... with DMX, it's the *position* in the datastream that determines which address a particular byte of data belongs to. So, even the channels that aren't being used still have to be there, as placeholders.