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Recommended RS232 to USB converters


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Hi Everyone,

Can anyone provide me with suggestions for reputable RS232/USB converters. Preferably I would like recommendations for converters using the PL2303 chipset (because I know it is well supported under both Linux and Windows). I would also like to hear members opinions on isolation or opto-isolation on these converters to ensure that surges and other nasty effects are not sent through to the expensive equipment connected on the RS232 side. As you can probably guess I lost some equipment due to a surge transmitted on the converter to batteries and inverters which fried the comms on these devices.

As a bonus, it would very much be appreciated if these were obtainable in South Africa. 


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I like the FTDI stuff. You can get them from RS, but they are a lot more expensive than others. You will probably find what you want at Micro Robotics (PL2303).

On opto-isolation: That could work but it is probably not going to be that simple - you need to arrest the surge and make sure it stops before the isolation barrier (on both sides) and have a fuse of sorts and enough distance to prevent breach. I have seen a number of very well designed isolation interfaces that failed to actually stop the surge from propagating simply because it is really difficult to do well in the real world.

I like the ADuM range of digital magneto-isolators for communication, but they require power on both interfaces.

Edited by P1000
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I saw the FTDI stuff on RS (because I buy there anyway for business reasons) but I was not sure if it would work. I am almost at the point where I would say cost is a minor/secondary issue simply due to the immense inconvenience/time/money involved when a surge damages the communications on some of your kit. 

It has taken months of haggling with the bank and quite a large amount of my own money to get my solar system back online.

I'll have another look at the FTDI and I will also read up on the ADuM (is that Analog Devices or just a coincidence?).

Thanks for taking the time to post.

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Thanks @P1000

I'm happy to report the FTDI converter works.

Results of dmesg

[160585.535658] usb 1-1.4: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[160585.535666] usb 1-1.4: Product: US232R
[160585.535672] usb 1-1.4: Manufacturer: FTDI
[160585.535679] usb 1-1.4: SerialNumber: FT4WLQTJ
[160585.571538] usbcore: registered new interface driver ftdi_sio
[160585.571583] usbserial: USB Serial support registered for FTDI USB Serial Device
[160585.571745] ftdi_sio 1-1.4:1.0: FTDI USB Serial Device converter detected
[160585.571823] usb 1-1.4: Detected FT232RL
[160585.574534] usb 1-1.4: FTDI USB Serial Device converter now attached to ttyUSB1

No reboot required. 

Next I'll try to make up a little breadboard with the chip you suggest above and play around to see if I can get it to work.

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  • 3 weeks later...

I had my communication board grilled when I connected simultaneously the Axpert(Synerji) RS232 and the Batteries BMS RS232 communication lines to the same computer. I found out the hard way that their ground references have about 10V difference. I would need an opto-isolator on at least one line. Actually I use 2 different laptops.

In order to prevent spikes or radio interference to enter the devices I equipped the lines an both ends with ferrite cores.

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