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daniel

The Serial Adapter

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Soo, I am here in Florida doing school, and I really want to be able to use my controller I brought down. However, I forgot my serial adapter! Now, until I get my adapter mailed down, which could be a month or more in time, I was thinking about making my own adapter. I did some Google searches and it looks like this adapter could be some kind of standard item that can be bought, or made quite easily.

Ref. http://images.google.com/images?q=rj45%20adapter




So heres the question, does Light-O-Rama have any special "guts" in the serial adapter, or would I be able to match a few pins on a serial and ethernet cable?


EDIT: http://techpubs.sgi.com/library/dynaweb_docs/linux/SGI_EndUser/books/SGIconsole_HW_CG/sgi_html/figures/pinout.RJ45-to-DB9.adapter.gif
This looks promising,



Thanks for any help!



--Daniel L

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Update, I went ahead and took the risk. The image I posted above is true, I followed it and I get communication! I can control the lights, but the hardware utility can't run the port check, or locate the controller. So I just typed in the info and it worked! Im almost positive their is another wire or two to connect to get the full functionality, but for my needs, this is perfect.


But if anyone has any additional info, please let me know!


Thanks!



--Daniel L

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There is a circuit in the LOR adapter. LOR communicates via 485 protocall. A serial port is RS232 communications. With the new upgrades most LOR boards can run on DMX commands with a adapter similar to your design.

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Now this begs the question:

Would a usb-> rs485 or a serial -> rs485 adapter work?

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Donald, good observation. Question is, why does what I did work? I do believe it is one-way communication because the hardware utility is not reading anything back, but the control works just fine.



Dr. J, I would NOT attempt the USB adapter like you said. USB is some kind of digital signal, and the serial port in analog I believe. If you are talking about a USB to ethernet port adapter, I have heard stories that using a live internet port will fry the controllers. As for the second suggestion, it is kinda like what I did yesterday, although I don't know the difference of a store-bought adapter (non-LOR).




Everyone else-> I did this at my own risk! I did weigh the risks, and I determined that the little power the serial port puts out would not be able to hurt the controller if something was wired backwards. (Remember, some of the controllers can put 12v back onto the line to power accessories). This should be considered a hack or modification and I would only recommend you try it on a real port on a computer, and not a USB device. I have no intentions of permanently using this hack for light control, but will be kept as a working reserve incase of a mid-show crisis.

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I am surprised and had to think about it for a while.

RS232 (which is what comes out of the PC) and RS485 are specifications that define how the electrical part of the communications is performed. RS232 and RS485 are very different electrically BUT the information being sent is being sent in the exact same format.

The LOR SC485 has a parts in it that convert the RS232 electrical signal into the RS485 electrical signal.

So why does it work? In theory it should not but we can toss theory out the window because it is working. I would be careful because 232voltages are much higher than 485 voltages. The RS485 chip could be damaged with prolonged use but they do build them pretty rugged so it may be okay.

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The USB to RS485 mini would work, but it costs $39.95. The LOR USB-RS485 Communications Adapter sounds like it does exactly the same thing, but it only costs $27.95. Not only that, but it's guaranteed to work with the LOR controllers and software, and it works with cables that have standard RJ45 connectors.

As to using RS232 in an emergency, the RS232 standard allows anything from 3 to 15 volts. The RS485 standards specifies a maximum of 6 volts. Most likely the chips in the controllers could take it. Also, RS232 is not differential like RS485, so its range would be limited. Also, as Daniel found, RS232 transmits and receives on separate pins, so the hardware utility can't "hear" the controllers. So yes, it will work, but it's not recommended!

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Ok

this is a little off topic. Do the LOR controllers have built in termination? Reason I ask, I have found several RS485 hubs that would allow a star topology, and if I go this route, I definately do not want any type of reflection

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We do not have a termination selection in the controllers. Becuase we use very heavy slew limited 485 reflection is not usually an issue. As you probably know you only need a terminator at the end of the chain and you could easly make your own by connecting the center two wires of the comm connector with a 120ohm resistor.

Dan

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