I was pulling a show down yesterday and I noticed two S4s ghosting. I asked the LD about it and he wasn't sure about why it was. I started to ask about it retaining a DMX signal and he cut me off. It seemed he thought since the DMX had been disconnected it couldn't happen. To be honest, I wasn't sure so I thought I would check. If the DMX is disconnected from the dimmer to the board, but is still connected from the dimmers to the trusses, can it ghost?
DMX Ghost
- Thread startermstaylor
- Start date
No, we were in a concert style setup. Sound,video and three trusses. Leprecaun board and dimmers. We were using an opto-splitter.
- The dimmers had a high preheat level set.
- The dimmers had a long hold last look set.
- DMX death gasp.
Three is what I suspected but my question is, does the board need to be in chain for that to happen or mearly the dimmers?
My guess is a combination of a "keep last look" setting on the dimmers and a DMX death gasp. Unless it was changing intensity, then I would guess something with the splitter/DMX line giving the dimmers different levels.
Little late apparently,
Not as far as I know. I've had it happen to me before that way.
Little late apparently,
Not as far as I know. I've had it happen to me before that way.
I agree with Chase about the "keep last look" setting. That's how our iSeries dimmers are programmed. They stay at whatever levels were last transmitted to the dimmers. If you happen to have a fader up just a little bit and don't notice it when you shut the console off, the dimmers will keep the light(s) at that level until you turn the board back on and lower the channels in question. Same thing would happen if you disconnected the control cable -- dimmers would maintain levels until they received further commands.
Using the Leprecon 600 series whatever level you leave your dimmers at after disconnecting the board from DMX will be held until the board is reconnected. One needs to make sure lights are completely out and not ghosting. I've had the "Noah the lights won't shut off" call way too many times from people using that board. Also there is some DMX death gasp, especially on that board.
Also OP, assuming they are just Source 4's, like your post said, there is no DMX that goes to the truss. DMX goes from the board to the dimmer pack and tells the dimmer pack how to power the lights. Only power comes from the dimmer pack and goes to the lights. You probably know this but your post made it sound like you didn't.
Also OP, assuming they are just Source 4's, like your post said, there is no DMX that goes to the truss. DMX goes from the board to the dimmer pack and tells the dimmer pack how to power the lights. Only power comes from the dimmer pack and goes to the lights. You probably know this but your post made it sound like you didn't.
I had the same thing occasionally happen with an express and sensor rack. I try to remember to unplug the dmx from console before shutting it down to prevent this though it doesn't aLways work at least I don't have to wait for the console to boot back up. What happens is there is a data glitch and it gets interpreted into a command and the dimmer will hold it as long ad it holds it's last look.
I know for a fact with the Sensor rack that's a feature, not a bug. It's "DMX A Loss Behavior" or something like that - the default is "Hold Last Look". You can change this though using the CEM+.
jglodeklights
Well-Known Member
Yes, it is a feature available on the Sensor racks, along with many other dimming packs and racks that default to a "Hold Last Look on DMX Loss". On Sensor racks you can alter the time which it will hold this look, or as Scott said, turn it off. Safety feature in case of a board failure so that the stage doesn't blackout. Also would work in the event that one or two phases of power to your building are lost during a show, including the one with the console on it. Many reasons we could come up for having it that way!
If your DMX/Analog converter is the last device in your DMX chain (i.e. you don't daisy chain through it to other devices) then you should have the termination switch set to ON all the time. DMX lines like to be terminated.
on some dimmers it is a design limitation you have to live with. There are only 8 bits available to control the level and there is variability in components. So it depends on how the phase control is mapped into the PIC and of course the leakage current through the optoisolator circuit - it may be enough to just turn the TRIAC on ever so slightly
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