CQRobot Passive RS232 to RS485 Converter Adapter, Bi-direction Transmission, Zero Delay, 600W Surge Voltage and 15KV ESD Protection, 115200bps Transfer Rate. for Industrial Serial Communication.

Part arrived quickly and was as described

I already have a USB to RS485 adapter, however I was getting quite annoyed that every time I plug the adapter into a different USB port the comm port number changes, and I have to reconfigure all my software tools. I reasoned that in the good old days every PC had a built in serial port which therefore had a fixed comm port number and the renumbering problem didn't arise. So, I added a PCI serial port to my PC and I bought this.At first glance I was rather disappointed with it. I saw terminals labelled R+, R-, Gnd and Vcc - which raises a number of questions:What on earth is R+ and R-? The standard designation of RS485 terminals is A and B. That's how the thing you want to connect to will be labelled. RS485 signals are bipolar, i.e. one signal is the opposite of the other, there is no plus and minus. And as for the 'R' I have no idea - the line is half duplex (used for both tx and rx) so R can't mean "receive". Not very encouraging to see poor labelling like this, however I'd be lying if I said it was the first time. Anyhoo, for future reference, connect A to + and B to -.Then there are the next two terminals: GND and Vcc. The heart sinks. Do I now have to run wires for a DC supply to power the thing? Ok, then what DC range does it want or allow? If you can find an answer to that second question then you're a better man than me (or you work for DTech).The absolutely great news is that you don't need those terminals at all: supplying Vcc is optional, the device can be powered by the serial port alone (probably from DTR, that used to be a common trick). I've seen the question raised of "well then why does it need a Vcc terminal at all"? Frankly I don't know, but I can speculate that it's a fallback if you have say a notebook that can't or won't supply enough juice (though these days a microcontroller can run on microamps, and I assume this dongle has one). There is also a known problem you sometimes get with RS485 if the sender and receiver are on different power supplies, there might be a voltage differential between them, which causes a current flow which interferes with comms. The fix then is to power both ends from the same supply, hence Vcc and Gnd to take power from extra cores in the transmission cable.Notice that the plastic case on this thing has a lip that intrudes around the sides of the RS232 connector. This may obstruct you from pushing the adapter all the way in to the socket on the backplane of some PCs. For me this isn't a problem since I don't like to have dongles sticking out of my PCs anyway - it seems obvious that they'll get broken off. Instead a use a serial cable, and then the dongle clicks into the cable and the plastic case isn't a problem.Last but not least, this device doesn't need the sending software to toggle RTS to control send and receive (line turnaround of half duplex). This is done automatically. The software still needs to be ping pong in nature (i.e. it musn't try to overlap send and receive), but provided it doesn't do that then line turnaround will be much faster and more reliable.All in all, this could well be the perfect RS485 adapter for those who want to use a dedicated PC RS232 port. It's such a shame that it doesn't come with a single scrap of paper telling you what it does!

Used to convert a few jbus 232 to Modbus 485 devices. Worked well.

good

Worked straight out of the box.

Old data standards, yet the design is exceptionally good. Over 100kbs across simple twisted pair cable 1.2km was reliable. Excellent noise rejection along with cross talk (near end, distant end or traversal. Wow i'm impressed. This has good environmental protection by fast reacting semiconductor devices (TVS) 15KV 600W ensures robust ESD protection and other EMC interferrence from industrial motors. Great for older CNC and Robotic control interfaces. I found even normal remote antenna control data link at 1km and highest rate set at 110kbs tge but error rate was 1x10-9 averaged over a month of 24x7 use. I'm impressed. This is a must have adapter for a wired link or orotocol conversion. Highky recommended, Andrew

Device did not work. Wasn't even worth the hassle of sending it back. Will not use this supplier again.Passive RS232 to RS485 Converter, Lightning Protection. Suitable for PC, Terminal Equipment, Industrial Control, Digital Instrument Collection, Multiple Serial Devices to Serial Interface Devices.

The interface is compatible with EIA/TIA's RS-232C, RS485 standards, safe operation, suitable for most current operating software and operating interfaces.