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Moving head pan causes DMX interference


fbnts

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Hi,

 

We have a lighting rig comprising of quite a few different fixtures all running on DMX. Recently we have been having issues whereby the strobe randomly flashed and the smoke machine would pump on its own.

 

I spent a few hours trying to work out what was causing it and after testing cables and fixtures along the chain I came to one of the I-Move 5s moving heads (we have two). When it was linked in every 10-15 seconds or so it would cause the above problems.

 

I then used the control software to hold the fixture. When it was held, it stopped causing the interference. I slowly re-enabled its features, gobo, colour wheel, tilt and then when I enabled the pan it started causing the interference again.

 

Has anyone experienced this before? Would it be a sign of the stepper motor dying or the motor driver circuit?

 

Tom

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I then used the control software to hold the fixture. When it was held, it stopped causing the interference. I slowly re-enabled its features, gobo, colour wheel, tilt and then when I enabled the pan it started causing the interference again.

Could you explain this a bit more? What control software are you using? How did you 'hold' the fixture?

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I then used the control software to hold the fixture. When it was held, it stopped causing the interference. I slowly re-enabled its features, gobo, colour wheel, tilt and then when I enabled the pan it started causing the interference again.

Could you explain this a bit more? What control software are you using? How did you 'hold' the fixture?

 

Sorry, I use Freestyler with the Enttec open DMX interface. In the software I selected the fixture, and select one colour and one gobo. I then position the beam to one position. This overides the preset sequence.

 

I can then release a channel, ie when I release the colour, it cycles through the colours of the sequence. Then the same with gobo and then the tilt. This leaves the fixture working as it should in the sequence except there is no pan movement until I release that channel. Thats when the problems occure.

 

Tom

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Thanks Tom.

 

Here's a bit of a clue perhaps...

When the DMX signal is off, the lights will switch to Master/Slave mode automatically.

Easy installation, easy addressing, and easy operation.

 

Pre-programmed function

Automatic switching between music trig or auto trig mode.

Master/ Slave mode :

I.) No need to designate which unit is master or slave, the first unit in the chain will always act as the master unit.

 

Your DMX line is terminated is it? And you're using decent tested DMX cables?

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Thanks Tom.

 

Here's a bit of a clue perhaps...

When the DMX signal is off, the lights will switch to Master/Slave mode automatically.

Easy installation, easy addressing, and easy operation.

 

Pre-programmed function

Automatic switching between music trig or auto trig mode.

Master/ Slave mode :

I.) No need to designate which unit is master or slave, the first unit in the chain will always act as the master unit.

 

Your DMX line is terminated is it? And you're using decent tested DMX cables?

 

 

Yes, we have a terminator on the last fixture. The cables are rated as DMX, but appear to be standard mic cables (I plan to at some stage replace them with twisted pair cable) but if I just bypass this fixture it is fine so pretty sure its not the cabling.

 

I have just been looking more at the light. I turned everything on, opened up the moving head and disconnected the pan motor. If I rotated it by hand all the way CW and then back CCW it would interfere with the DMX signal during the last 20 degrees of the turn. That eliminates the actual stepper motor and driver circuit.

 

The lamp cable and signals to the head go through the centre of the light and I think it was something to do with these. I have check that they are not damaged, and although the sleeving shows signs of rubbing, it hasnt gone through to the cable. However, when I put it back together, its not creating the fault now!?

 

I will leave it switched on tonight to see how it gets on, if it still causes the problem, I will take it down and look at the wiring loom properly.

 

Tom

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I turned everything on, opened up the moving head and disconnected the pan motor.

 

Just for the record, don't disconnect a stepper motor with the power on. It is an effective way to blow its driver chip and you've been lucky! Power off first, pull its plug, then apply power if necessary.

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I turned everything on, opened up the moving head and disconnected the pan motor.

 

Just for the record, don't disconnect a stepper motor with the power on. It is an effective way to blow its driver chip and you've been lucky! Power off first, pull its plug, then apply power if necessary.

 

 

Oh sorry, yes I had it powered down. I don't like touching anything while powered up.

 

Tom

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It sounds like the rotation is causing something like a dry joint or cracked PCB to cause the input DMX signal to fail. This then put the unit in master/slave mode and causes it to generate a DMX signal which upsets downstream devices.
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Thanks for all your replies.

 

When the PC shuts down the two moving heads do go into master/slave mode but do not affect any of the other fixtures so don't think its that..

 

Its part way through the chain however the fault affects all devices in the chain. I think my final option if its not cured is to get a isolated DMX splitter and run this one fixture on its own.

 

Tom

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