Lights work wirelessly but not hard wired.

[Leftylampie]

It's not an earth loop as the controller is class two (no earth) and I've tried with the ground lifted at one end of the DMX cable (that didn't work).

 

I think that DrV has probably hit the nail on the head and it's something that I'll have to work around, i.e. only use this combination of fixtures/controller wirelessly and use a different desk in the rare situation where I have to hard wire.

 

Thanks for everyone's help. It is appreciated.

[alistermorton]

I'm probably wrong, but if the fixtures are class 1 and there are multiple erroneous earths, could that cause a hum loop in the cabling?

[sunray]

I have a similar issue with these: https://www.amazon.co.uk/Sanfiyya-Decoder-Controller-DMX512-Channel/dp/B096M456FY/ref=sr_1_4?dchild=1&keywords=DMX+led+decoder&qid=1634650735&qsid=259-7342232-5735755&s=industrial&sr=1-4&sres=B096M456FY%2CB093PJX1MY%2CB09H286W4L%2CB09GKMCTCN%2CB0919S8MHD%2CB07XY8YQPS%2CB09C7Z6FQM%2CB091SZVQN1%2CB092DKN5QN%2CB09D3MH95H%2CB09D7PPGVP%2CB09D3R2GTF%2CB0828D63QD%2CB09J913B38%2CB09DKLLB74%2CB08XQMLLZQ%2CB0919VCRWV%2CB08XQLNPR9%2CB08XX92SVL%2CB091CQ3SNN 3ch decoders, which will only work on one of my 3 desks

[Leftylampie]

I have the same issue with just one PAR can connected. :-(

 

I'm probably wrong, but if the fixtures are class 1 and there are multiple erroneous earths, could that cause a hum loop in the cabling?

[alistermorton]

How infuriating.

 

DMX speed?

 

 

[timsabre]

How infuriating.

 

DMX speed?

 

 

 

I think you said a few posts ago that putting the wireless tx unit in line between the controller and first parcan fixed the problem. This makes me think it is something electrical rather than a timing problem, since the tx unit will just be a pass through.

 

If you have the controller and the first parcan running but not plugged into each other, and you measure voltage between pin 1 on the the controller and pin 1 on the parcan, do you get a surprising voltage there?

 

 

[Leftylampie]

That's an interesting thought. I'm away from home now until Thursday, I'll try that then and let you know the outcome.

 

How infuriating.

 

DMX speed?

 

 

 

I think you said a few posts ago that putting the wireless tx unit in line between the controller and first parcan fixed the problem. This makes me think it is something electrical rather than a timing problem, since the tx unit will just be a pass through.

 

If you have the controller and the first parcan running but not plugged into each other, and you measure voltage between pin 1 on the the controller and pin 1 on the parcan, do you get a surprising voltage there?

 

 

[DrV]

How infuriating.

 

DMX speed?

 

 

 

I think you said a few posts ago that putting the wireless tx unit in line between the controller and first parcan fixed the problem. This makes me think it is something electrical rather than a timing problem, since the tx unit will just be a pass through.

 

If you have the controller and the first parcan running but not plugged into each other, and you measure voltage between pin 1 on the the controller and pin 1 on the parcan, do you get a surprising voltage there?

The reason I suggested timing is that the only wireless DMX kit with which I am familiar (CTI) does indeed re-time the packets. I don't know about the budget end of the market - do they simply transmit the logic levels without doing anything to them?

[sunray]

Earth loops 'shouldn't' matter as DMX runs on a balanced system... Shouldn't...

 

I tried allsorts to get the decoders I mentioned earlier to work on all desks including optoisolated splitter, lifting ground, linking grounds, running device or desk on battery/generator etc. What I didn't get around to doing was looking at the system with a silly scope.

 

[Jivemaster]

Officially RS485 which is the cabling protocol used for DMX requires that the screen be considered zero volts and the two conductors should be balanced also and the signal be referenced to the screen. If the screen is fed by a psu at each end then problems can occur. This sometimes happens if the data ground is connected to mains ground and mains ground is at different potentials in different places. Of course if -as by wireless- there is no connection between data grounds there is no problem.

 

Very few DMX systems appear to be fully compliant, many systems work if not quite right, some do not.

[timsabre]

How infuriating.

 

DMX speed?

 

 

 

I think you said a few posts ago that putting the wireless tx unit in line between the controller and first parcan fixed the problem. This makes me think it is something electrical rather than a timing problem, since the tx unit will just be a pass through.

 

If you have the controller and the first parcan running but not plugged into each other, and you measure voltage between pin 1 on the the controller and pin 1 on the parcan, do you get a surprising voltage there?

The reason I suggested timing is that the only wireless DMX kit with which I am familiar (CTI) does indeed re-time the packets. I don't know about the budget end of the market - do they simply transmit the logic levels without doing anything to them?

Ah good point. Most stuff I have seen just links through the DMX without any processing.

 

[alistermorton]

The reason I suggested timing is that the only wireless DMX kit with which I am familiar (CTI) does indeed re-time the packets. I don't know about the budget end of the market - do they simply transmit the logic levels without doing anything to them?

 

That was my thinking too (different product, though).