RS-485 to USB adapter

B

Thread Starter

bill

Hello,

Does anyone have a good recommendation for a RS-485 to USB adapter? I have a York Chiller that uses Simplicity for alerts, etc., which is merely a MODBUS network, as I understand it. I'd like to avoid the use of Simplicity and just read the registers, coils, etc. myself (via libmodbus or Perl's Modbus::Client, e.g.). But first, I need a physical means of bringing in the signals to my PC - thus the adapter question.

Any suggestions or use cases?

thx,
-bill
 
Can't you use a USB-RS-232 adapter and then use a RS-232 <-> RS485 adapter? I also noticed that Startech makes a USB-422/485 converter.

KEJR
 
Bill,

B&B makes a port powered RS485 x RS232 xverter, and Belkin and Staples have a USB to RS232 xverter, you should be able to put these two together and have yourself a USB to RS485 converter for under $150.

~Robbie
 
Thanks to all for your responses. So I take it that the product billed by York/JC to do the job, the Source 1 FREEnet USB Adapter, does nothing more than convert USB to RS-485? In that case, I reckon I'll save myself ~$800 and go with one of the "generic" USB to RS-485 adapters that one can find online...

thanks,
-bill
 
F

Fred Loveless

The one thing that I have found to be an issue for my customers is that the USB to RS485 converters can sometimes be under powered so that lines are not raised and lowered properly.

Resolving that problem usually requires a USB to RS232 converter with a RS232 to 485 converter that can be externally powered.

Fred Loveless
Kepware Technologies.
 
The other approach, if you're worried about power, would be the use a USB to RS485 adapter (FTDI makes them, you can find them on Digikey or Mouser, and they are available in a number of lengths with tinned wire ends) plugged in to a powered USB hub.

I've never been pleased with the USB to RS-232, then RS-232 to RS-485 process, but if you need more power than what USB can deliver, you'd have to go that route. If you have potential problems with ground loops, there are opto-isolated RS-232 to RS-485 converters.

Lots of solutions.
 
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