DMX PUZZLER

[tij5987]

Hi Guys,

 

Bit of a DMX issue that is causing me problems;

 

Every year I end up working at my old school, lighting their annual musical - for my sins!!! It is at this time of year you realise how well equiped my venue truly is!!!!

 

I am using a Strand 300, running GeniusPro and both DMX outputs on the desk. Second output goes to a horrid dimmer (DPX 610 if that means anything to anybody!?!) using 5pin DMX then converted to three pin to go into the dimmer rack. Out of the dimmer rack and into a Showtec LED parcan (as you can tel - all quality equipment here!!!) out of the can into a Mac 250 Wash (slightly better I suppose!) and then into a further two Mac 250 Wash's and then into another three Showtec LED Pars.

And so the chain looks like

 

Desk -> Dimmer Rack -> LED -> Mac -> Mac -> Mac -> LED -> LED -> LED

-5 pin DMX-- 5 to 3 pin ----------------------- 3pin DMX -------------------------

 

 

The second universe has no problems and serves other dimmers(install not the same as above) , Macs and LED cans with 5 to 3pin converters etc also.

 

The problem with this universe however is that channels randomly flash on (with no human intervention) be it the dimmer channels (not all at once randomly different channels at different times), intensity of the Macs will flash on, and also the LED cans will flash on also (worth noting the LED's don't have an intensity attribute). Also the first Mac on the string will take itself into reset from time to time. However everything responds to the desk just fine.

 

I have tried eliminating everything including;

 

- Swapping the outputs on the desk and repatching accordingly

- Toggling the second universe settings in console set-up between 1-512 and 513-1024 (never sure which it should be as although both universes are in use everything could fit and has been addressed to fit on one universe - maybe someone could fill me in???)

but the issue remained the same

- Bypassing the dimmer pack on the DMX run, but the intelligents still randomly flicker and flash the same

- Swapping Cable that runs from desk to dimmer rack

- Swapping the converter

 

But the problem always persits, I really am at a loss. All I can think of doing that I havn't already is adding a terminator to the end of the run, or (and I know its a long shot) switching the DMX polarity somewhere like before the dimmer rack say???

 

Basically I am really stuck, think I have eliminated everything that could be an issue apart fom the two above things?

 

Could anyone offer an insight or any other suggestions? Might the above help?

 

Would be most grateful as ever for anybodys advice and help.

 

Many Thanks,

 

Tom. (ps appologies if there is any dodgy typing or spelling, it's nearly 3am and my fingers are strapped up following an unpleasant injury!!!)

[dbuckley]

It sounds like random garbage, so a terminator is an excellent first step.

[Roderick]

I agree with David, first step is to terminate the DMX feed.

If that doesn't help, one of your LED's or MAC's may be causing the problems. As the problem exists when you bypass the dimmer you could safely eliminate that.

I would first see if the LED's or the MAC's have problems by connecting only those to the desk (first - 3 x MAC, second - 4 x LED)

If either of those groups still flicker, start unplugging one by one until it stops and then connect all just bypassing that unit. If that cures the problem, have the identified unit checked.

If neither the MAC's or the LED's flicker on their own they may not like to be in the same universe (who could blame them :blink: ) and an opto splitter may be required.

Last step is to replace all the DMX cables, it only takes one bit of dodgy DMX cable to really stuff things up.

 

Best of luck!

[vl nick]

What DMX cable are you using?

 

If its microphone cable then you have your problem, however a terminator should clear this up.

[ben.suffolk]

The LED cans, when not receiving DMX will generally react to sound. In this case they probably output some form of DMX. The Eurolite ones I have output DMX of some sort to control the other LED cans when the DIP switch is not set to DMX mode.

 

It could well be that one of you LED cans is faulty, maybe has a dry joint on the DMX dip switch, so it randomly outputs a bit of DMX which is corrupting the output from the desk.

 

I would be tempted to bypass all the LED cans, check that you no longer have problems, then bring them back in 1 at a time until you find the faulty one.

 

Regards

 

Ben

[Ynot]

Hi Guys,

 

Bit of a DMX issue that is causing me problems;

Join the club!

I've been getting very occasional bursts of noise on our DMX network for a while now without any success at tracing the problem.

Difficulty with our fault is that we have an 8-way opto splitter at the desk end feeding 4 lines out to FoH and stage, but we get the spurious c**p on all lines - have changed, as you have, cables etc to no avail. My thoughts now are that there's something being outputted from the 300 itself.....

:blink:

[tij5987]

Thanks for your suggestions,

 

However,

 

- Termination doesn't solve the problem.

- Have followed Roderick's suggestion again with no luck, and worth noting that the other universe has Mac's and LED's on it (6 Mac's and 8 LED's) with no problems.

- All cable is DMX, not regular microphone cable.

- Have briefly had a go at Ben's suggestion and all seems ok, but will look further into that.

 

So errrrrm I'm confused to say the least!

 

Problem sounds similar to ynot, are you also using a 300 that it causing such problems? Does it appear to be just the one string of DMX (feeding the spitter) but the other output with units/dimmers etc is fine. Then if you try swapping the output on the desk, the problem moves to the new output?

 

So, I guess I will keep you informed. Any other suggestions appreciated though.

 

Tom

[JohnMac]

Another long shot for you, check the polarity of the MAC equipment. The old roboscan lanterns had the DMX +ve, and DMX -ve pins (Pins 2 & 3) swapped around.

 

If the MAC's are in the middle you may need to invert the signal into the first lantern, and then convert back to normal as you come out of the last of the Martin equipment.

 

Assume that you're using cables specified for DMX, and that you have a terminator fitted.

 

Also worth checking is excess cable being looped up / around mains cables, steel lighting bars. (Transformer effects).

 

Regards

 

John Mac.

[david.elsbury]

Another long shot for you, check the polarity of the MAC equipment. The old roboscan lanterns had the DMX +ve, and DMX -ve pins (Pins 2 & 3) swapped around.

But not the mac250 wash units- they are new enough to be "correct"

[dbuckley]

If you have a chain of stuff, then the best way to fault-find a chain (any chain, not just DMX, works with audio, power, anthing in a line) is the age old method of the binary chop.

 

Break the system in half in the middle. Is the half nearer the desk working now? If so the fault is downstream of the split, so put the split back, and move half way to the end and split again. If the fault didnt go away, then split half way to the source.

 

Its the optimal solution to solve a general line problem. Works just as well with the "think of a number between 1 and 100", I pick a number, you say higher or lower...

[Paul_R]

Having had some experience at ynot's venue, I can confirm that they do indeed have a 300.

 

The 'standard' dimmers are on Universe1 and the 'intelligents' are on Universe2.

Not sure if the outputs have actually been swapped, but I know different cable and a different splitter have been tried.

 

The problem manifests itself as LED fixtures 'flash' and the two Goldenscan mirrors 'jump' out of position on the pan and back again.

 

As in ynot's case I believe the Goldenscans and LED's are on different outputs of the opto-splitter it should be the case that if one of the LED's was faulty it could not affect the Goldenscan.

 

I have an Enttec USB Pro and assuming the LED light on it goes some way to indicating DMX traffic, I have noticed that when recieving on Universe2, the LED flashes much faster than when I use it to output DMX at other venues from my laptop. Sadly I did not try plugging into Universe1 to compare.

Based on this and other experience I did wonder if it was worth trying a lower DMX frame rate, but I did not look into if this was possible or how to do this on a 300.

 

So any Strand gurus able to tell me if I can and where the option is?

 

Tom - Perhaps if you can get hold of a splitter and cabling is not a nightmare, it would be worth trying a splitter to see if it helps isolate the problem, i.e. Dimmer(s) on 1st output, Macs on 2nd Output, LED on 3rd output Etc.

 

Thanks,

Paul

[Kazeja]

Recent (?) Strand consoles, 300/500 have the facility to terminate on the rear of the console/brain. (DMX in facility).

 

Have known DMX devices to go crazy and misbehave when the output(s) of the console have been terminated locally using the switch on the rear of the console. Check that DMX (switch) is "NOT" set to terminated on rear of console. Termination LED should be off.

 

Also, with "everything" switched off and if you have access to a meter, measure the resistance between DMX+ and DMX- on the connector that plugs into the rear of the 300 brain. A reading of 120 ohms +/- 20 ohms is acceptable. Anything less than 100 could cause problems.

[ben.suffolk]

Have known DMX devices to go crazy and misbehave when the output(s) of the console have been terminated locally using the switch on the rear of the console.

 

Thats odd, because technically an RS485 Bus should be terminated at both ends (for the transmitter can in fact be anywhere on the bus, not just at one end as it generally is on DMX).

 

However if the console has 2 DMX ports on the same universe, this can be done by connecting the ports together thus in effect having the transmitter in the middle of the of the bus. Obviously if this is the case you do not want to terminate by the TX.

 

Ben

[Kazeja]

Yes Ben I agree.

RS485 should technically be terminated at both ends.

 

From reality though, I know there are some DMX devices out there which you cannot daisy chain and will not work with a termination at the transmitter. It is just something to experiment with or check for in this case to see if it solves the problem.

 

Also, your remark about having 2 DMX ports on the same universe. The DMX ports are linked in software not hardware so in this case the brain can be treated as a buffer. Maybe I misunderstood your point.

[Ynot]

An 'out of the box' thought here - our 8-way splitter as I said uses just 4 outputs, the others are left clear.

I wouldn't have expected those remaining ports to need a terminator each - or would they... ? - after all, they're supposed to be isolated, yes?

 

EDIT:

Well, blow me.

That off the wall thought may not have been so off the wall....

Re-reading the manual for the splitter it does in fact say the all outputs need termination....

Guess who'll be soldering this weekend...?!!

 

This was a surprise!!