DMX Adapters; Another 5 pin to 3 pin DMX question

[RichMoore]

I have seen in previous posts regarding 5 pin to 3 pin DMX conversion questions, to just use the first 3 pins on the 5 pin to connect to the 3 pins of the XLR connector, since the 4th and 5th pins were vacant or not used at all.

Since my in-house DMX uses all 5 pins of the connector and the cable is 2 twisted pairs with braided shield, how would I connect to the 3 pin connector? I have tried using only one of the twisted pairs with no luck. I am thinking that I need to use the positives of each pair and the negatives of each pair to connect to pins 3 and 2 with the shield still on pin 1.

Does that make sense? Has anyone else done this? Am I way off base? What is the solution?

[waynehoskins]

Both pairs are a differential RS-485 serial data channel. You can't common them to each other.

Data Channel 1 is the one that's used for outbound control data. That's pins 2 and 3 (2 data complement, 3 data true) .. backwards from the audio wiring convention.

What are you trying to hook up to what? It's possible (nay, probable) that the 3-pin device isn't DMX.

[derekleffew]

Originally Posted by RichMoore

...Since my in-house DMX uses all 5 pins of the connector...

By "in-house DMX," to what are you referring? The cabling? All DMX512A-compliant devices only use pins 1,2,3 of the 5pin XLR. All devices using 3pin XLR to carry DMX, while technically non-compliant, should have no issues provided the adapters are wired one-to-one. Note that early Martin gear (i.e., PAL-1200s) and a few others required pins 2&3 to be swapped.

Here is the current DMX standard: ANSI E1.11 - 2004, and here is a link to adapters I have found useful: Audiopile.net.

What are you trying to control, and with what?

[ishboo]

I have a 5-pin DMX-512 board and a couple devices that are 3-pin. I picked up a couple adapters on ebay for about $3/ea and haven't had a single problem since.

[TimMiller]

In many installed they will wire up pin's 4 & 5 but they are not physically used. Using turn arounds will not cause any problems.

[porkchop]

I have to agree with Derek totally. In theory (although as mentioned it's against the standard) all you need is pins 1-3. Your house wiring may be 5 wire but as far as you board's output is concerned pins 4 and 5 are basically vacant of useful information. There are exceptions to this, the pyro I work with uses what we call "true 5 pin DMX" that is 5 wire cable that sends two sets of information so as to provide error checking (or something like that haven't truly looked into it), but as far as the standard is concerned that is not really DMX, that's an offshoot that uses some similar equipment. If you're using modern lighting gear that takes 3 pin information it shouldn't matter that you actually have 5 pins in your house system.

[RichMoore]

A bit more info and hopefully clarification on my issue.

I am running a Strand 520i....into which, I wrote the attributes of the new fixtures into the fixture library....red, attribute 14...green, attribute 15...blue, attribute 16....

My DMX cabling is 2 twisted pairs with braided shielding soldered to pins 1 thru 5 on 5 pin connectors....

All DMX signal goes through Path Port/ethernet....

I have been provided with 7 LED Par type units which have 3 pin DMX input and output connections....

I have been provided with 3 pin male & female connectors and with 5 pin male and female connectors, along with cable that is 2 twisted shielded pairs...

I am fabricating cables to daisy chain the LED units in order to control the color output of the fixtures....

I have taken a short 5pin DMX cable and cut it, so that I have a male with a short length of 2 twisted shielded pairs and a female with a short length of 2 twisted pairs....

I soldered into the1, 2, and 3 pins of 3 pin connectors the twisted pair and the shield that are connected to the 1, 2, and 3 pins of the 5 pin connectors....

I then connected the 5 pin male into the PathPort output and connected the 3 pin female into the LED 64unit DMX input....then I connected the 3 pin male into the LED 64unit DMX output and inserted a DMX terminator into the 5 pin female...

Using the rotary controls on the 520i, I was able to only control the red output of the fixture, and that went from red to black.

I am presuming that the simple way around this issue is to try the store bought 5 to 3 converters, but seeing as how I am an old poot, I know there must be another way, although not quite so simple.

Any ideas or not so simple solutions?

Thanks,

Rich Moore
Technical Coordinator
Performing Arts Center
Texas A&M--Corpus Christi
Corpus Christi, Texas

[waynehoskins]

Me believes your problem is not in the adapter. If you were able to control anything about the fixture, there's data getting to it, and it's just RS-485, so if it was able to make out anything of the control signal, then it's probably good.

Methinks your problem is either in the fixture addressing or the library in the board.

[RichMoore]

Thanks for the response Wayne.

I will revisit the fixture library and double check what I have written.

I am now wondering about the dip switches on the back of the LED 64units. I may have inadvertently juxtaposed the #10 switch with the #1 switch. I will give that a shot also.

Thanks again,

Rich

[JD]

Also check for dyslexia !

More than once I have ended up with 2 & 3 reversed even though I was positive I did it right! When the dmx is reversed, you get some odd behavior, not quite dead, but nothing like normal.