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DMX Data


dekw1

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I am playing with a Kam 800 panel and an un-named Led mover . I have beside me an IMG Stageline 1440 controller, a Geni DM4 controller and a Laptop running Freestyler through a JMS USB2DMX dongle .

All the Dip swiches are set correctly to start at channel 1, and the polarity of the DMX outputs are all the same.

The laptop will control the Kam but not the mover (the head will not stop in one position and the LEDS only strobe ).

The Stageline will control the mover, but not the Kam.

The Geni will control both.

My DMX test plug led flashes slower with the output from the Laptop dongle.

Any ideas?

Cheers.......Dek. :P

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I've got a terminator in even though I'm only 2 meters away.

I can't understand why the Laptop output should make the tester flash at a slower rate than the other 2 controllers. I thought that all DMX signals would be the same Frequency..............

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I've got a terminator in even though I'm only 2 meters away.

I can't understand why the Laptop output should make the tester flash at a slower rate than the other 2 controllers. I thought that all DMX signals would be the same Frequency..............

 

Not necessarily. The DMX spec can actually tolerate things which are really slow, just usually it sits around 35 / 40Hz which creates smooth enough movements for most applications. Can't remember off the top of my head the lowest limit for frequency, but its not that high!

 

The MTBP (make time between packets) can be up to 1s as far as I remember, so if theres a longer delay between the packets, it'll flash slower.

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Certain PC based controllers vary the DMX output rate depending on what is happening on the DMX stream - if the data is steady (no changes) then the frame rate drops down to as low as 1 Hz - this is acceptable in the DMX standard and most DMX receiving devices accept this with no problems. As soon as a change occurs, the DMX rate jumps back up to a 'normal' rate to facilitate the crossfade. This reduces the overall processor load and helps make multi-universe systems more stable.

 

It's nothing to worry about and shouldn't cause you any problems :)

 

 

 

Peter

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Regarding Freestyler, did you write the fixture files yourself (personalities). I ask because many of the included personality files with FS are incorrect in my experience. You're better writing them from scratch yourself.

The Stageline & Geni of course don't have personality files.

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