Mydmx Problem

How many fixtures are you running total? DMX has a physical limit of 32 fixtures/dimmer packs per universe. Beyond that, weird things start happening. Also, how long is your cable run? I am going to assume you aren't using a DMX splitter/booster which might also be the problem. USB dongles don't put out as powerful a DMX signal as a hardware console (its a voltage thing mainly it seems). That might be why when you added the two lights, things start acting weird because the two extra lights pushed you over that threshold.

I am running 12 led par cans 2 360s total run was 50 feet to the first tree then jumped to the other 2 trees,25 feet each.

So you are using about 150 ft of cable total assuming 5' jumpers in between fixtures. Think it is time to look into a DMX Splitter. Elation makes two, the DMX Branch-4 and the Opto Branch 4. One of these will most likely solve your problem (barring something else like a bad cable).

Well that sucks,My jumpers are 3 foot also what I do not understand if this is true Why is it the back rack being 2nd in line was having the problem but the front 2 racks were fine and 1 front rack was last in the line?

your using actual DMX cable or mic xlr cable?

mic xlr cable

Use DMX.
If you wanna know why, I'll tell you about my weekend.
Sincerely,

Ok, now tell me why and about your weekend

lol ok. So I was at a Audio installer company who is getting into lighting installs too. They had a 50 foot dmx cord going up to their square rig truss design. ALL cables were microphone cable. the total run was probably around 150 feet including 5 foot cables going from fixture to fixture. This was a smallish rig too. 2 mover. 2 scanners 10 led pars. NOTHING worked at all. Even taking out their 50 foot main cord and using my dmx cables to go up to the first fixture I had regained SOME control of the fixtures but they were reacting erratically. I took out the cable going to the rest of the fixtures that were all hooked in via mic cable and voila I got control of 2 fixtures that had my dmx cables going just to them. Mic cable just won't work. make sense?
Sincerely,

Ok, so it looks like I need to get some bulk dmx cable. I just don't understand why that the rig was working fine then went haywire, then a reboot and all but the one worked the rest of the night.

Mic cable isn't shielded like DMX is. It also has a different impedance value. It simply was picking up some sort of interference and then the signal on the reboot was powerful enough to cut through it.

I like to tell this story a lot. My former boss once ran a set of Octo Strips with just a single 25' mic cable into the console and the strips wouldn't respond to DMX. He swore up and down it had to be a bad cable and replaced it three or four times, each time with no success. Whatever was going on in that room simply didn't allow even that short run to work.

There was also another time in which he ran one dimmer pack DMX and then about 150' of XLR around the room to the other dimmer pack. The first dimmer pack worked fine, the second didn't respond at all. I walked in after he setup the next day and put a DMX splitter inline right next to the first dimmer pack and the second plugged straight into the splitter. The second dimmer pack then worked fine. It also would have worked fine if he had used DMX instead in the first place like he should have. Reason I used the splitter is because the cable was buried and needed to go right into a show.

Ok I have 2 questions, one could this be the problem I have 2 front trees 4 par leds mirrored of each other 1 - 4. Now I added the back rack 4 4 par leds and the 2 360 leds. I ran to the first front tree then the back then over to the other front tree, I am wondering if this could of caused the problem. Second question could the use of DMX splitter improve this situation

Thanks,
Jim

Yes a DMX splitter will GREATLY improve your situation.
Look at the Opto Branch 4 from Elation.
http://www.elationlighting.com...gory=DMX%20Solutions
Sincerely,

A splitter does 3 things. First, it boosts the DMX signal. This means it can push through more interference and longer lengths of cable. Second, it splits a DMX signal. This allows you to save on cable lengths and runs. In stead of having to create one, massive chain, you can break it down into smaller chains. The last thing a splitter does is it isolates the DMX signals between each line. This means that interference on line A won't effect line B or your home run line (line which goes to your controller). Also, if you get a signal spike down a line, it won't damage the DMX drives on the other lines and on your controller as well.

It is a very good and useful investment. I often times end up using more then one on many of my shows. I would recommend one to anyone with a light show, especially ones that are looking to expand and add more fixtures on.

You might also want to pick up a couple of DMX Terminators. They are cheap and can often times help solve signal problems. Also cheap insurance as well as they can prevent signal problems in the first place.