Can we use these to make out light show work?
Ron:
There are two types of DMX dongles -- the Enttec Pro and the Lynx DMX dongle are "smart" dongles, whereas the Enttec Open (the one you listed from eBay) is the "dumb" type.
DMX needs to constantly be spitting out its 512 channels of signal -- over and over again, thousands of times a minute, whether there's a change in the data or not. Most of the time a DMX signal is 512 zeroes. The smart dongles have microchip inside them that handles this signal generation. The dumb dongle is expecting the PC to handle this signal creation.
PCs in general and Windows machines in particular don't do something called "pre-emptive multitasking" well, which means that if your PC is doing something else, it might not remember to be always generating your DMX signal. That something else could be as mundane as updating your screen clock or checking with Redmond about OS updates. So your DMX signal falters, which can cause a stuttering effect with your lights (or maybe nothing; it all depends on the randomness of when the signal is interrupted).
In his early experiments with DMX, RJ found that that the dumb dongles just didn't create a good Christmas light environment. That's not to say they didn't work, just that they didn't work well. He bought an Enttec Pro and found that it worked well on a consistent basis.
He didn't like the price, so he designed an Enttec Pro clone on his own, reverse-engineering it.
Which is a long way of answering your question, which is to say, "maybe."
But, if I were going to try an Open DMX dongle, I'd probably just start with a plain vanilla USB-RJ485 converter, which runs as low at $5 on eBay, rather than spend $60 on the device you listed.
Best o' luck.
\dmc
