DMX Optical Isolation

[kidcole]

I am planning to use the 4th Universe from one of my E681s for my DMX output to the yard. And my DMX channels are entirely comprised the little 3 Channel China controllers from Holiday Coro (currently 18 of them) but may grow to 30 before the "lights come on."

I am concerned about having my E681 running with a fairly large 150W 12V power supply .. and then directly driving the DMX output to all the China controllers. Therefore, I am thinking it would be smart to put a DMX Opto-Isolater repeater on the E681 DMX output. This would assure any electrical surges would not traverse either way between my DMX and my E681 pixels.

I am looking for comments on DMX isolators if anyone has experience with them. I know that some of them can get quite expensive (even over $200) .. If I wanted to spend that much I could have purchased the ENTTEC Pro ... except I don't want any more USB interfaces! LOR will be on the USB :-)

Here's one in the $40 range on eBay.

http://www.ebay.com/itm/270672760246...84.m1423.l2649

Is this a good idea or a bad idea ? Does anyone know of DMX isolators for a better deal ? Maybe a group buy?

[n1ist]

Something looks odd on the power supply for that board - they have two regulators and two bridge rectifiers, but only one power input. That defeats the purpose of optical isolation.

Should be easy to make one; a 75176 as a receiver, 6N137 opto, and another 75176 as a transmitter. Use the same isolated 5v supply that's on RPM's or RJ's dongle.

[Added: Just tossed this schematic together for one... There's one typo in it - R1 should be 4k7 or so, not 220R...]

/mike

[smartalec]

N1ist that design looks great.
Looks like the design ive been working on , but im also using dc-dc converters as well an made it a 8way
here is my design, altho im currently having a issue with it, but i will sort it out one of these days

If someone can see my mistake i would be realy greatfull.
also i made a board as well
http://memberfiles.freewebs.com/26/77/82227726/photos/undefined/dmx splitter board-3.png
I thought it was time i gave back to the DIYC community

[n1ist]

The 75176 has a reasonably wimpy driver on RO (looks like Iol is only 8mA) so it can't drive all of those LEDs in the optos. You will need to add a buffer - a 74LS541 would work well.
/mike

[David_AVD]

Here's one in the $40 range on eBay.

http://www.ebay.com/itm/270672760246...84.m1423.l2649

That one will probably do the job, but it appears to require either two power transformers, or one transformer with two separate secondaries.

[mschell]

Denny,
Note that the power feeds from the E681 aren't tied to the data feeds. You wouldn't have to worry about any power surges coming from the E681, since you wouldn't be (or shouldn't) connecting the power leads from that last cluster to the 3-channel controllers.

Having isolation on the data feeds is good for not having induced surges from long cable runs effect upstream controllers, or having something go wrong on your 3-channel controllers get fed back to the E681.

[tfischer]

Can the E681 supply straight DMX data? I knew the ELOR could, but not the E681. Does anyone have info on how this works?

[budude]

Can the E681 supply straight DMX data? I knew the ELOR could, but not the E681. Does anyone have info on how this works?

It can - you have to build your own RS485 converter though (basically the same chip used on the Rens) since it's just a 3.3v level (or 5v if using the buffers) data stream - not RS485 coming out. There was a post a while back but haven't seen much on it recently. You set the E68x to "Raw DMX" or something similar using the "CHIP" command.

[Matt_Edwards]

The opmanusl tells you. You simple use chip yo option 5.

Sent from my GT-I9100 using Tapatalk 2

[kidcole]

I appreciate all the good replies. It would be awesome if one of you made a raw card and a BOM for a nice DIY DMX opto-isolator. I think it's worth using them to isolate the different types of DMX devices. And particularly anyone using some nice DMX units such as the scanners, and cool effects lights. I could see kits for a single and then maybe some variations such as one in two out .. or one in and four out.

I think i would also be nice to come up with some "best practices" suggestions for where DMX opto-isolators should be used ..

That one will probably do the job, but it appears to require either two power transformers, or one transformer with two separate secondaries.

Thanks David. I sent this question to the seller. I'll let every one know if he replies...