If you work in the event lighting industry then you'll probably have experienced DMX network issues and the mayhem they can cause. One of the biggest weaknesses of DMX is the lack of error detection and the annoying ability to function under fault conditions with random instability.
The most common problem is a shorted or broken data line in a network, and this simple tester can detect many of those issues.
Note that this tester will not analyse the validity of a DMX stream, although it's very rare that there is a data timing or format issue unless the shadiest generic lighting desks are used.
It will also not indicate a reversed data pair, although that's often fairly obvious in a run of lights.
I use one of these at work and it does a great job of tracking down faulty cables quickly.
Note that officially you are supposed to terminate a network by plugging a connector with a 120 ohm resistor in it at the end of the run of lights. The resistor bridges the two data lines and reduces the risk of signal reflections that can corrupt data at random points in the network. It's not uncommon for veterans of the industry to imply that they actually cause problems. In reality the terminator will most likely show a problem that was already there. For instance, if a broken cable left one of the data pairs floating the lights might still work with just one line, but when the terminator is connected it stops the rogue line floating and brings it to an equal voltage with the good line. That results in no differential voltage and no data, causing the lights to stop working.
The coloured connectors were bought from a UK supplier called CPC which is part of the Element 14 group, so I would expect the same connectors to be available from their other outlets around the world.
Here are some connector purchase links for the UK.
For the 5 pin male XLRs the codes are:-
Red - https://cpc.farnell.com/pro-signal/psg01320/xlr-plug-5pin-red/dp/AV14488
Yellow - https://cpc.farnell.com/pro-signal/psg01322/xlr-plug-5pin-yellow/dp/AV14490
Green - https://cpc.farnell.com/pro-signal/psg01323/xlr-plug-5pin-green/dp/AV14491
Blue - https://cpc.farnell.com/pro-signal/psg01321/xlr-plug-5pin-blue/dp/AV14489
Black - https://cpc.farnell.com/pro-signal/psg01319/xlr-plug-5pin-black/dp/AV14487
For the 3 pin male XLRs the codes are:-
Red - https://cpc.farnell.com/pro-signal/psg01310/xlr-plug-3pin-red/dp/AV14478
Yellow - https://cpc.farnell.com/pro-signal/psg01312/xlr-plug-3pin-yellow/dp/AV14480
Green - https://cpc.farnell.com/pro-signal/psg01313/xlr-plug-3pin-green/dp/AV14481
Blue - https://cpc.farnell.com/pro-signal/psg01311/xlr-plug-3pin-blue/dp/AV14479
Black - https://cpc.farnell.com/pro-signal/psg01309/xlr-plug-3pin-black/dp/AV14477
Quarter watt 220 ohm resistors:- https://cpc.farnell.com/unbranded/mcf-0-25w-220r/resistor-0-25w-5-220r-pk-100/dp/RE03795
And whatever bright red LEDs you can find, noting that eBay generics are fine.
Choose a bright connector colour to make it easier to spot in amongst the blackness of the industry. I keep mine on my keyring at times to make sure it's always with me. The slight downside of that is the risk of inadvertently leaving your keys plugged into a light!
If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:-
http://www.bigclive.com/coffee.htm
This also keeps the channel independent of YouTube's advertising algorithms allowing it to be a bit more dangerous and naughty.
The most common problem is a shorted or broken data line in a network, and this simple tester can detect many of those issues.
Note that this tester will not analyse the validity of a DMX stream, although it's very rare that there is a data timing or format issue unless the shadiest generic lighting desks are used.
It will also not indicate a reversed data pair, although that's often fairly obvious in a run of lights.
I use one of these at work and it does a great job of tracking down faulty cables quickly.
Note that officially you are supposed to terminate a network by plugging a connector with a 120 ohm resistor in it at the end of the run of lights. The resistor bridges the two data lines and reduces the risk of signal reflections that can corrupt data at random points in the network. It's not uncommon for veterans of the industry to imply that they actually cause problems. In reality the terminator will most likely show a problem that was already there. For instance, if a broken cable left one of the data pairs floating the lights might still work with just one line, but when the terminator is connected it stops the rogue line floating and brings it to an equal voltage with the good line. That results in no differential voltage and no data, causing the lights to stop working.
The coloured connectors were bought from a UK supplier called CPC which is part of the Element 14 group, so I would expect the same connectors to be available from their other outlets around the world.
Here are some connector purchase links for the UK.
For the 5 pin male XLRs the codes are:-
Red - https://cpc.farnell.com/pro-signal/psg01320/xlr-plug-5pin-red/dp/AV14488
Yellow - https://cpc.farnell.com/pro-signal/psg01322/xlr-plug-5pin-yellow/dp/AV14490
Green - https://cpc.farnell.com/pro-signal/psg01323/xlr-plug-5pin-green/dp/AV14491
Blue - https://cpc.farnell.com/pro-signal/psg01321/xlr-plug-5pin-blue/dp/AV14489
Black - https://cpc.farnell.com/pro-signal/psg01319/xlr-plug-5pin-black/dp/AV14487
For the 3 pin male XLRs the codes are:-
Red - https://cpc.farnell.com/pro-signal/psg01310/xlr-plug-3pin-red/dp/AV14478
Yellow - https://cpc.farnell.com/pro-signal/psg01312/xlr-plug-3pin-yellow/dp/AV14480
Green - https://cpc.farnell.com/pro-signal/psg01313/xlr-plug-3pin-green/dp/AV14481
Blue - https://cpc.farnell.com/pro-signal/psg01311/xlr-plug-3pin-blue/dp/AV14479
Black - https://cpc.farnell.com/pro-signal/psg01309/xlr-plug-3pin-black/dp/AV14477
Quarter watt 220 ohm resistors:- https://cpc.farnell.com/unbranded/mcf-0-25w-220r/resistor-0-25w-5-220r-pk-100/dp/RE03795
And whatever bright red LEDs you can find, noting that eBay generics are fine.
Choose a bright connector colour to make it easier to spot in amongst the blackness of the industry. I keep mine on my keyring at times to make sure it's always with me. The slight downside of that is the risk of inadvertently leaving your keys plugged into a light!
If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:-
http://www.bigclive.com/coffee.htm
This also keeps the channel independent of YouTube's advertising algorithms allowing it to be a bit more dangerous and naughty.
Awesome video, and device !!!
Question, what does it indicate if both LED's are ON full, not flashing ???
And my lighting control software – Vista – still seems to work ok… but I do have a leg/universe that does not light or is not controllable – the leg with both LED's on full…
Aww, i wanted to see that video. Oh well….
Great little tool. Would it cause any issues having this circuit permanently installed in a dmx line?
Dude I use this every day. It's a 3 year old video but if you hear me. I'm a mechanic so troubleshooting is the same
Is it possible to make one of these with a 120Ω terminator resistor built in?
Excellent stuff! I was able to follow thus tutorial and make my own, which works great!
Any suggestions for making something similar to test for existence of (+48v) phantom power..?
TIP: instead of using glue u kan use the plastic cable grip and the little washer (or a metal washer) to fix the leds
From what I understand, the – is measurement.
This is awesome. Thanks so much for sharing.
Great little design. Question could this be used to test a 3 Core RS485 system. As DMX is a form of 485. The RS485 3 Core uses a 3 Pin XLR Pin1
Screen Pin2Data – Pin3- Data+Could you use a different colour led on each pin to give you an idea of which wire was faulty? Red pin 2 and green pin 3??
Does this tester also work as terminator?
Didn't mess with DMX, all our clubs were small and smokey and well, arguably illegal…cough, but I did wrestle with midi repeaters and honestly I really could have used a TTL light based "This shit is not actually dead" tester. Good call. Beats licking the end. What? What's that?, future potential reader? Don't judge! in the middle of a wood when you gotta get that amp/spot/genny running no-one is quoting H&S. One time I pulled a three inch thorn right out of a guys eye and he went back to dancing (I insisted he let me sluice it first at least.Yes, I take saline into a woods)
fumbling? perhaps a florist's sponge block?
Nice tutorial! Will certainly make one. Does it double as a terminator?