Elite freezing

[Emilio]

Hi,

I need some help, please.

I have a permanent colour light installation that uses an Elite MKII, pcb ver 2.2, currently running firmware rev 1.10. The Elite runs a colour chase sequence in standalone mode. Ocasionally the user may chose to hookup a computer and change the sequence but this never happened so far. The installation is supposed to never shut down and nobody messes with it, i'm sure.
The problem that occured is that the DMX output from the Elite quits occasionally and the 5Vdc  power to the Elite must be turned off and on again for the DMX output to recover.

The light system was first turned on at the beginning of July 2009 and it kept on working without a glitch until late October when, one day, it froze for the first time. Since then the freezing keeps happening every 1-3 days.

What i did trying to fix the problem:

Updated the firmware from 1.05 to 1.10
Rebuilt and reloaded the sequence
Inserted a glitch filter on the 5V dc power line (5Vdc comes from the wall adaptor that is plugged in its own, dedicated, wall outlet).

No difference, i just got another call from the user's site saying that the lights froze once again.

Any suggestions or tips would be greatly appreciated.

Emilio

[Maarten Engels]

Sorry to here about this issue, let's try to resolve it.

Has anything changed in the lighting system around late October; change in cabling, different fixtures, anything altered?

[Emilio]

Hi Maarten, thanks for replying.

No, no changes at all. One day it just quit and I got the dreaded phonecall

Since posting here i figured a few more details:

After a power on-off reset of the Elite only (can not reset the receivers and lights part) all is normal for a while, ranging from 20min to hours. Then i get the phonecall
I got the chance to actually see how it fails. Some receivers start losing signal first, the lights become flakey, then more receivers lose signal and after a while all receivers lose signal. (The DMX receiver behaviour is set to go dark in absence of DMX signal).
The Elite does NOT lock up, the track # display changes from the buttons. 
I tested the DMX pair and ground for shorts, none found.
I powered the Elite from a separate power adaptor and the voltage was verified as steady 4.97V

I have a sneaky suspicion that the time interval after the reset 'till bad things start happening has been decreasing lately, this should be good news actually, maybe it comes to a point when the problem, whatever that is, will become possible to replicate on my test bench.

Of course, the customer is all over my back, but they are patient so far.

Any ideas what to check/try? LOL

Emilio

[Maarten Engels]

Just a few thoughts...

How many dmx fixtures are connected to the elite? less than 32?
Do you use shielded twisted pair dmx cable? no 'microphone' cable?
Do you use a 'terminator' at the end of the dmx line?
Could you try inserting a optically isolated dmx splitter/booster at the beginning and/or middle of the dmx link to see if it changes the situation?

[Emilio]

Hi,

There are 5 receivers connected to the Elite.
The DMX cable run is about 5 metres long.
The cable is Cat5  with 4 twisted pairs
The DMX signal goes through one twisted pair.
The other used pair carries 5Vdc from the adaptor.
The other 2 pairs are grounded.

However, after playing some tricks with pull-up and pull-down resistors on the DMX wires and doing some research in the rs485 biasing theory I figured that the output driver in the MAX1480 was not working right. (B line was toggling correctly between 0-5V but A line was only pulling High, as if the pulldown mosfet was not coming on). So, i tricked A output with a 3Kohm pulldown, which fixed the problem temporarily. That was almost a month ago...it still works.
I bought a new MAX1480 from Digikey, but never got around to replace the supposedly faulty one in the Elite...I'm not going to until it stops working again

I shall keep you posted, thanks.

Merry Christmas!!!

[Maarten Engels]

Good research, well done! Maybe the MAX1480 is damaged, doesn't happen often but, it everything can break at some point. Am I right in thinking the MAX1480 is socketed? (Not in the office to check) Hopefully that makes it easy to replace.

Please let me know if you need any assistance from our side.

Merry X-mas to you too!