Control/Dimming LED's blink off and on at randon times

[dougemc]

Hello:

Controlling 32 channels through 4-8 channel dimmer packs via DMX. Added 4 LED fixtures to the last dimmer via Belden twisted pair to XLR. P1/ ground, P2/DMX -, P3/DMX +. DMX XLR cables used to daisy chain the 4 LED fixtures and terminator installed at end of chain on last fixture. Tested numerous times and all wiring seems OK.

Using Lightfactory 2.1 through USB Pro DMX. It all seems to operate fine - BUT...

At a random time within any of our light queues one or 2 of the 4 LED fixtures will go off and then on without any apparent reason. The dimmer pack controlled "conventional" fixtures are rock solid.

1-32 are patched to the dimmer pack fixtures. 33-43 patched to 1 LED moving head, 44-54 patched to a 2nd LED moving head and 55-59 are patched for the last 2 strip light LED's (both set to channel 55 controlled identically).

It makes no sense. It must be something simple but I am pretty new to this.

Thanks in advance for any suggestions!

 

[derekleffew]

...At a random time within any of our light queues one or 2 of the 4 LED fixtures will go off and then on without any apparent reason.

Is it the same one or two fixtures or are they all doing it a various times? You never see a "glitch" except during a fade (up, down, or color change)? Try setting all four LED units to the same address and see if they all exhibit the same behavior.

What make and model are the LED units in question?

Some "lesser quality/lower cost" fixtures are not fully compliant with the DMX standard. I doubt LightFactory allows the user the lower the DMX speed, but that may be a solution. See also Check me here guys...(Jands Vista/Chauvet ColorStrip).

 

[dougemc]

We are a church so high dollar stuff is not real possible. The fixtures are Irradiant - from China. They are supposed to be DMX compliant.

2 fixtures are identical RGB LED moving heads and the other 2 are RGB LED strip lights.

The moving heads are addressed differently.

The strip lights are addressed identically.

The blink does not happen during a fade up/down/transition. We are locked in and then it just randomly blinks off and back on quickly.

The majority of the time it is the strip lights. Occasionally one of the 2 moving heads will do it - and even reset it's position although less frequently.

I do have access to the USB DMX Pro Box and can alter the rate at which data packets can be sent but haven't gone here yet.

Thanks for your suggestion. I will look further. Feel free to share any further - I do appreciate it!

-doug

 

[soundman]

The majority of the time it is the strip lights. Occasionally one of the 2 moving heads will do it - and even reset it's position although less frequently.

Because the movers are rehoming it might be that there is a dip in the power. Unless the movers are getting some data on the control channel they only thing that would make them rehome is being power cycled. Try running just the board, and one of the lights with one data cable. This should eliminate a lot of issue but will let you know if the gear is working. If you have another board great, that will help you test the signal.

 

[Rob]

Dougemc,

First, check your cable terminations. Make sure you have proper termination at the end of the run, and also make sure there aren't any terminators turned on in the middle of the run.

Second, slow down the output speed of your DMX. 30 - 35 packets per second should be enough, but you should also check that the USB DMX Pro is increasing the inter-bit and the Mark-after-Break time, not simply extending the idle time between packets. Also, make sure the USB DMX Pro is updating at the same rate when nothing is going on. Some computer-based DMX distribution systems only update as necessary, instead of fully streaming, when nothing is changing.

We have been seeing a number of problems with the manufacturers of low-cost LED fixture using inferior RS485 transceiver chips. These chips just can't keep up, lose track of where the packets start, and can't recover until they've gone through signal loss. The best answer (other than returning the gear as non-compliant) is to slow the DMX down.

Robert Armstrong
Pathway Connectivity

 

[kendal69]

I understand you may not want to spend money BUY you may have to. Check out Doug Fleenor:
The DMX2DMX addresses issues associated with non-compliant DMX devices. Many lighting devices claim to accept DMX512 signals, but are unable to support the wide variety of timing parameters allowed by the DMX512 standard. The result is flickering, flashing, or erratic operation. The DMX regenerator addresses these issues by receiving any DMX512 signal, buffering the data, and then re-transmitting the data under a well-defined set of timing rules. In addition to this, the input is fully opto-isolated to provide protection and to break potential ground loops.

One you can do on your own is seperate the DMX address by more than in needed. If it's a 6 channel make the first light (1) and the next light (10) or (12) and on and on - separate the signal by more than (1)

How do I know I just went through this with Cheap Chinese lights they are NOT compliant even if they say so.

 

[LuxMax]

This may go against conventional wisdom, but try removing the terminator at the end of the line and see if anything changes.