Control/Dimming Lighting newbie with probably a stupid question

[thomas rehm]

Hi Guys,

My school just purchased supplemental lighting for our auditorium in the form of 2 lighting trees with 4 ellipsoidals each, both controlled by D4 DMX dimmer packs. We already have a working dimmer rack that connects to our strand 200 console. The question is, can the lighting console control all of these dimmer packs/racks at the same time? It doesn't appear to be able to, since there is only one DMX output on the back, which has been taken by the dimmer rack. Is there a way around this? My problem:

Is there an adapter I need or am I overlooking something here? Thanks in advance for any help...

 

[derekleffew]

1. If there is a "DMX out/thru" on your existing dimmer rack (and that is convenient for you), come out of that and daisy-chain into your shoebox dimmers.

2. If the above is undesirable or impossible, you'll need to place an opto-splitter at the console.

3. In either case, be sure to use a terminator, DMX at the end of each run. Terminating unused outputs on the opto-splitter is NOT necessary.

 

[thomas rehm]

There is an input 1 and input 2 on the dimmer rack. Is that an DMX out/thru? I think they're 5-pin...Thanks for the tips and definitely on the terminator...

 

[petercav17]

If there are two inputs, then no that would not be a dmx out/thru, but maybe it could be configured as such? But guessing that your dimmer rack is probably far away, the easiest thing would be to do what Derek said above and use an opto-splitter. However, if you cant get one, you could always send your dmx run to the little packs first, and then out of them to the rack.

 

[len]

Even if there is only an input on the rack you can still chain all d4 packs and the rack together. You just need to run from one to the next to the next, in whatever way makes the most sense for cable runs.

A splitter usually has an amplifier in it to boost the signal, and that would be a good idea.

You may have more than one output for each universe from the board, in which case that might help shorten cable runs.

You may have more than one universe of dmx at the board, in which case putting the rack or the dimmer packs on universe 2 might also shorten cable runs.

Put a terminator on the ends of the runs, after the last dimmer.

A dmx signal is not like putting multiple speakers on a single cable, where it changes the impedence and all that (can you tell I'm not a sound guy?) . There is a limit on the number of dmx devices on a single chain (24, I think) but your rack and 2 shoebox dimmers is far short of that. Remember, the lights are not devices in this case.

Also, if you're referring to Leviton D4DMX dimmers, they really should only have 2 fixtures per pack. Each dimmer channel may be rated at 600 watts, but the power cord is probably rated for less than 1800 watts, and your typical 15 amp wall outlet is barely 1,650 watts, if that. Be safe and plan for less wattage per pack.

 

[robartsd]

There is a limit on the number of dmx devices on a single chain (24, I think) but your rack and 2 shoebox dimmers is far short of that. Remember, the lights are not devices in this case.

DMX spec supports 32 unit loads and a run of up to 1200 meters. These days many DMX chips don't require a full unit load, so in some cases even more devices could be daisy chained, but that is not recommended. An opto-splitter could make running your DMX lines easier and would protect equipment connected to one port from damage due to faults in equipment connected to other ports.

 

[JD]

Check with the manufacturer of the rack to see if those two "input" connectors are simply jumped together. If so, it would be ok to daisy chain out of it. It is also important to make sure the rack is not internally terminated. If so, the rack should be the last device on the chain, or the terminator should be turned off and a terminator plugged into the last device on the chain.
Now, here comes the part when I get brutally executed by my peers: If:
A) the rack is not internally terminated
B) there is no other way of doing it
C) you keep the wires very very short
D) you never install anything between this and the rack
If, And I repeat, IF all of the above are true, you could make a Y adapter.
Y adapters are a no-no in DMX land as any cable forming a second branch after the Y will set the stage for standing wave problems. Still, a Y adapter is basically what in in-out jack combo on a rack or fixture is. When it is inside the fixture, the manufacture can be sure that the wire length between the jack plate and the electronics is short enough to not create a problem. Usually this is along the lines of 2 or 3 inches. A free standing Y is risky because sooner or later, someone moves it elsewhere and all hell breaks loose.

 

[lwinters630]

Hi Guys,

My school just purchased supplemental lighting for our auditorium in the form of 2 lighting trees with 4 ellipsoidals each, both controlled by D4 DMX dimmer packs.

Have you checked with whoever ordered these packs on how they planned on connecting them? Also the 4 ellipsoid 2300W are pushing the limit on a 20 amp circuit. The D4 is only rated to 2400w. If you plug it to a wall outlet that has other power draws on it the breaker will trip. Check your load and run.

 

[robartsd]

Also, if you're referring to Leviton D4DMX dimmers, they really should only have 2 fixtures per pack. Each dimmer channel may be rated at 600 watts, but the power cord is probably rated for less than 1800 watts, and your typical 15 amp wall outlet is barely 1,650 watts, if that. Be safe and plan for less wattage per pack.

Also the 4 ellipsoid 2300W are pushing the limit on a 20 amp circuit. The D4 is only rated to 2400w. If you plug it to a wall outlet that has other power draws on it the breaker will trip. Check your load and run.

The individual dimmers on Leviton D4DMX are rated 1200W, the pack is rated 2400W, but the controling limit is the 15 amp power cord. Assuming your elisoidals use 575 watts 115 volt lamps, using more than three of them concurrently is a no go. If your elipsoidals are lamped above this, you should never use more than 2 concurrently on one of these packs. (Connecting four to the pack but using them at different times would work, but a board operator could accidentally turn them all on causing a problem.) You also have to account for any additional loading on the circuit the pack is connected to.

 

[petercav17]

You also have to account for any additional loading on the circuit the pack is connected to.

This. I remember doing a show one time in a small black box where the only light was from a leprecon dimmer pack, and I hadn't accounted for other equipment on the same circuit (since I had no way of knowing really) and halfway through one show, POP goes the breaker. Had to run like a madman in the dark to reset it. Fun times.

 

[Zebulon1880]

The short answer is run a daisy chain.

 

[len]

(Connecting four to the pack but using them at different times would work, but a board operator could accidentally turn them all on causing a problem.) You also have to account for any additional loading on the circuit the pack is connected to.

Which is why you should never exceed the total load on a dimmer. Not only do you put the circuit breaker at risk during the show you risk damage to the dimmer pack.