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» Film-Tech Forum   » Operations   » Digital Cinema Forum   » Xetron Maxi-12XPC automation and DMX triggering

   
Author Topic: Xetron Maxi-12XPC automation and DMX triggering
David E. Nedrow
Master Film Handler

Posts: 368
From: Columbus, OH, USA
Registered: Oct 2008


 - posted 12-16-2014 09:04 PM      Profile for David E. Nedrow   Author's Homepage   Email David E. Nedrow   Send New Private Message       Edit/Delete Post 
My current setup has a Christie IMB connected to a JNIOR, which is then connected to a Maxi-12XPC. Using macros defined in the IMB, the JNIOR is queued to momentarily close circuits for lighting (up or down) and audio format.

I have a number of LED PAR lamps that I'd like to use to illuminate our screen between shows. These lamps are DMX controllable.

I rigged up a "controller" using an Arduino and DMX Master Shield, such that it will read the state of the queue circuits and fire DMX commands depending on which queue closes.

I basically have four input pins (all white, all off, fade up, fade down) with pull down resistors. This causes the Arduino to run the inputs as normally open. When a pin goes to ground (closing the circuit) it fires a DMX command to the appropriate light fixture(s).

Here's where I'm a little unsure of myself. The simplest connection would be to simply hook the ground on the Arduino to the MAXI12XPC ground for the light functions, and each of the pins to the appropriate queue line on the automation. The Arduino runs at 5 volts, with the IO pins at 40mA.

Would it be safe to connect this to the same relay points on the Maxi that the JNIOR is connected to? I basically want to allow the Maxi to continue to control the incandescent house lights, while the Arduino controls the DMX stage lights using the same JNIOR queue routine.

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Harold Hallikainen
Jedi Master Film Handler

Posts: 906
From: Denver, CO, USA
Registered: Aug 2009


 - posted 12-16-2014 09:38 PM      Profile for Harold Hallikainen   Author's Homepage   Email Harold Hallikainen   Send New Private Message       Edit/Delete Post 
The 40mA sounds like an output current, not an input current. If you put a voltmeter between the input and ground, what does it read? If you put a mA meter between the input and ground, what does it read?

Harold

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David Buckley
Jedi Master Film Handler

Posts: 525
From: Oxford, N. Canterbury, New Zealand
Registered: Aug 2004


 - posted 12-17-2014 12:43 AM      Profile for David Buckley   Author's Homepage   Email David Buckley   Send New Private Message       Edit/Delete Post 
OK....

quote:
I basically have four input pins ... with pull down resistors. This causes the Arduino to run the inputs as normally open. When a pin goes to ground (closing the circuit)...
Now this cant be. It sound like you have pull-up resistors, not pull-down. This is quite important.

quote: David E. Nedrow
The simplest connection would be to simply hook the ground on the Arduino to the MAXI12XPC ground for the light functions, and each of the pins to the appropriate queue line on the automation. The Arduino runs at 5 volts...
Now if your Arduino project currently uses pull-ups to 5V, and the MAXI12XPC also has 5V pull-ups, then yes, by commoning your grounds, removing your pull-ups, and connect your switch wires to the MAX thingie then it should all work. You need to check with a meter that the Max thing uses 5V inputs, if not (other possibilities, 12V, 3.3V) the the smoke may escape.

Check that the power you are supplying to your Arduino is floating; there could be bad interactions with the MAXbox.

This could be nasty, as your LEDs on the other end of the DMX line will have a local mains ground connection, and so you'll get a ground loop through the Arduino to the MAXbox. These ground loops could do a lot of damage.

The easiest way out of this conundrum is to have the poiwer to the Arduino floating (or, indeed, steal it from the Max thing) and optoisolate the DMX feed before it heads off to the LEDs. To do this you could either construct such an isolator yourself, or purchase an off-the-shelf isolator.

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