Hi, thank you for all the good info on this forum. In the past, I've occasionally stumbled across this place from Internet searches and found useful advice.
Now I'm doing electrical work for an upcoming art installation for an event. After doing research, I'm still wondering about a few details that may or may not affect the reliability of the lighting system. It would be nice to be confident ahead of time that everything will work properly without problems from RF noise or ground loops, instead of having to fix issues during the installation. Maybe someone here can offer some advice. Here's the general setup:
DMX will be sent through shielded cat5e cable. It's a foil shield with drain wire, not a braided shield. Cable will be running in the same ceiling and wall spaces as Romex power wire. There is no metal conduit.
The generator will be at least 50 feet from the structure.
Opto-splitter: it's unclear whether/how signal ground is connected to earth. When it arrives, I can measure the direct current resistance.
There will be 4 DMX lines of 175 to 275 feet each, with 4 to 8 receivers on each line and terminators at the ends.
On some receivers, the signal ground is directly connected to the shield. It would be a pain to change this, involving a dremel tool and epoxy, but not impossible. I would likely break a few cutting wheels because it's a tight space between the jacks and the circuit board.
On other receivers, I can choose how or whether to connect signal ground to earth ground. For example, a 10nF cap, nothing, or direct connection at 1 receiver if nothing else on the same run makes that connection.
DC switching power supplies: signal ground is connected to earth ground via a capacitor of unspecified value in the schematic.
From what I've been reading, it's ideal to connect signal ground to earth ground with low impedance (less than 20 ohms) at the DMX transmitter only and high impedance (greater than 22 Mega ohms) connections at the receivers, although direct connections at receivers are sometimes okay but discouraged because of ground loop issues. It's unclear to me whether the shield should be connected to earth ground at one location only or if it can or should connect at every fixture.
If all these details are too time-consuming to analyze for some random stranger on a forum (me), I would be curious to just hear personal experience on when RF noise and ground loops actually cause problems and when it's generally okay to not bother following the strict recommendations. Of course, technical advice would be greatly appreciated as well.
Thanks in advance.
Now I'm doing electrical work for an upcoming art installation for an event. After doing research, I'm still wondering about a few details that may or may not affect the reliability of the lighting system. It would be nice to be confident ahead of time that everything will work properly without problems from RF noise or ground loops, instead of having to fix issues during the installation. Maybe someone here can offer some advice. Here's the general setup:
DMX will be sent through shielded cat5e cable. It's a foil shield with drain wire, not a braided shield. Cable will be running in the same ceiling and wall spaces as Romex power wire. There is no metal conduit.
The generator will be at least 50 feet from the structure.
Opto-splitter: it's unclear whether/how signal ground is connected to earth. When it arrives, I can measure the direct current resistance.
There will be 4 DMX lines of 175 to 275 feet each, with 4 to 8 receivers on each line and terminators at the ends.
On some receivers, the signal ground is directly connected to the shield. It would be a pain to change this, involving a dremel tool and epoxy, but not impossible. I would likely break a few cutting wheels because it's a tight space between the jacks and the circuit board.
On other receivers, I can choose how or whether to connect signal ground to earth ground. For example, a 10nF cap, nothing, or direct connection at 1 receiver if nothing else on the same run makes that connection.
DC switching power supplies: signal ground is connected to earth ground via a capacitor of unspecified value in the schematic.
From what I've been reading, it's ideal to connect signal ground to earth ground with low impedance (less than 20 ohms) at the DMX transmitter only and high impedance (greater than 22 Mega ohms) connections at the receivers, although direct connections at receivers are sometimes okay but discouraged because of ground loop issues. It's unclear to me whether the shield should be connected to earth ground at one location only or if it can or should connect at every fixture.
If all these details are too time-consuming to analyze for some random stranger on a forum (me), I would be curious to just hear personal experience on when RF noise and ground loops actually cause problems and when it's generally okay to not bother following the strict recommendations. Of course, technical advice would be greatly appreciated as well.
Thanks in advance.