I thought it would be worth looking in one of these units to see if it follows the rules for proper buffering of a DMX512 (one direction RS485) lighting network as used in the theatre and show industries.
It turns out that the circuitry is quite standard with a proper MAX485 receiver and 8 matching transmitters, but it's also a bit odd in that the circuitry is clearly based on a fully isolated buffer, but with the isolation defeated by the use of a single power supply.
With an application like this I would recommend swapping the supplied power supply for one from a reputable supplier. That way you can choose one amply rated for the task, plus avoid any isolation issues that could cause data corruption or damage other devices on a network.
Here's a typical search link on ebay com to find these units. :-
http://www.ebay.com/sch/i.html?_from=R40&_sacat=0&_sop=15&_nkw=8+channels+output+dmx512&rt=nc&LH_BIN=1
If you enjoy the channel you can help support it with a dollar for coffee, cookies and lighting gadgets for disassembly at:-
http://www.bigclive.com/coffee.htm
It turns out that the circuitry is quite standard with a proper MAX485 receiver and 8 matching transmitters, but it's also a bit odd in that the circuitry is clearly based on a fully isolated buffer, but with the isolation defeated by the use of a single power supply.
With an application like this I would recommend swapping the supplied power supply for one from a reputable supplier. That way you can choose one amply rated for the task, plus avoid any isolation issues that could cause data corruption or damage other devices on a network.
Here's a typical search link on ebay com to find these units. :-
http://www.ebay.com/sch/i.html?_from=R40&_sacat=0&_sop=15&_nkw=8+channels+output+dmx512&rt=nc&LH_BIN=1
If you enjoy the channel you can help support it with a dollar for coffee, cookies and lighting gadgets for disassembly at:-
http://www.bigclive.com/coffee.htm
I would LOVE to see a full laboratory test using all of the kit.
Rapid Electronics and RS Components are trade only and are not available to the General Public. In Ireland we had Peat's of Parnell Street for components and hifi. They have closed their store in Parnell Street and now THEY are trade only.
"hmmm interesting", that generally means, " what a load of c^&*p". And it seems it is 🙂
Great video thank you was thinking of getting one. As I find dmxing easier this way than daisy chaining
been tearing my har out troubleshooting randm flashing/twitching of lights in a venue. been fine for a while. would come in and it would be fine, then other days it happenns.
im not a lighting tech, recently discovered that dmx cabling is different to audio xlrs, so thats 1 issue, then found out that after certain amount of fixtures need a bufffer.
we have 16 movers, 14 led pars…
i never installed the cabling, did give instructions but it wasnt followed, the pars got installed first and wired up, then movers were added, pretty sure instead of goinng from first closest light and going round, they just wennt from last light…. cabling far too long
I have one of these. Works pretty decent.
Could you draw a circuit diagram of it please?
What is the purpose of the bridge rectifiers in a DC circuit?
I've been using this for ages, works well! Thanks for the video
Hello… podrías decirme cuál es el fusible IN de energía
Tengo este mismo SPLITTER y se quemo ese fuse
Tnk u
DON'T BUY THIS DMX SPLITTER. Some months ago sometimes It started to went crazy and 4 days ago it killed 2 of my moving heads. I think it sent some voltage over DMX.
hi clive good day, can i use a 18.5 VDC 3 amp adaptor on this unit?
Ground differences are ALWAYS present. We cannot avoid them. Power cables act as transformers that induce currents to ground prong so you cannot eliminate ground voltages between grounded electric equipments. Eliminate grounds connections means serious electrocution danger. (There is a good text if you like, easy to read "UNDERSTANDING, FINDING, & ELIMINATING GROUND LOOPS IN AUDIO & VIDEO SYSTEMS" written by Bill Whitlock, you can find on Jensen transformers site).– In this case we try to feed a clean DMX (or audio) signal to the equipments. The opto isolator at the input is a good way to RECEIVE a clean dmx signal using the pseudo balanced (or fully balanced if the dmx controller out is fully balanced) cable. A star connection to different dmx equipment (as is this splitter) always create ground loops because connects together the equipments grounds at the outputs of the splitter via dmx cables. The only way to not connect equipment grounds togheter shoud be an opto isolator at the input of each MAX485 and a separate (not grounded) power supply for each of them. Or one only power supply and a transformer on each output. Obviuosly these are expensive methods. Fortunately DMX is not audio signal and is inherently protected by his "high" voltage (compared to an audio signal) and by balanced cables. —
I use this splitter in a theater to receive the dmx signal after 50 mt of dmx cable and feed 2 different lines of dmx fixtures. It regenerates dmx signal and avoids overload dmx connection splitting it with different buffers on the outputs. For the price is more than i expected.
Full isolation is just an illusion. All DMX equipments have a ground connection that ties one to another indipendently by the dmx cable. The point is that dmx cable is balanced and the opto isolator led sees the voltage difference between dmx pin 2 and 3 with absolutely no reference to ground or earth. It's like pseudo-balance in audio cables (ex. Shure radio mics do it). Doing so it can cancel common mode interference and ground loop problems.
Is DMX just based on Midi?
Would you recommend to buy this for a little theatre scene?
Thanks for posting!
I really like the explanation, and now I’ll buy this dmx splitter
is this board glued in?… that's a bit …… TACKY!!!! genius