RS485 (differential) to single-ended

[bernie_carlton]

We are attempting to interface an AD H0-CTRIO counter to a system which has a differential (RS485 driver) quadrature encoder signal. We need to convert from the RS485 level signal to the single-ended (9 to 30 VDC ON signal) necessary for this counter. I don't want to build anything so I don't want schematic diagrams. I'm looking for an already made industrial convertor. There are pleanty of RS485 to RS232 converters out there but I need the single-ended output. Any references?

 

[randylud]

Possible!

Bernie, Have you looked at Blackbox?

 

[bernie_carlton]

I have tried B&B and they have a RS485 to TTL but I need it to go all the way to the high level (9 - 30 VDC) required by this counter card. The ones at Blackbox seem to be RS485 to RS232 which is even farther away from what I need. I'll keep looking though - thank you.

 

[Derek McFarland]

Try BEI

Opto-Isolator

 

[kamenges]

I've had pretty good luck using off-the-shelf solid state relays like these. You want to make sure any SSR you choose can handle the frequency. But outside of that you should be golden.

Keith

 

[bernie_carlton]

So far Derek's suggestion seems the best - will keep you informed.

 

[bernie_carlton]

Just to follow-up, as I promised, the isolator/convertor from BEI (as suggested by Derek) was the solution. The counter module is the CTRIO for the AustomationDirect PLCs. The folks at AD and at Host Engineering (who make it) didn't have any advice for me when I asked for signal conversion devices but this turns out to be the best soluution.

 

[elevmike]

Question:

Why not just replace the encoder with one that's compatable with the counter module?

 

[bernie_carlton]

The system being monitored by the counter module was two servos in a Master-Slave configuration. We were tapping off the differential command lines between the master and the slave.

The normal system has two pushers moving a case through a machine. They are coupled together mechanically with the system being driven by a normal 3 phase AC motor. The regular encoder is coupled by means of a small chain.

This system was such (I am told by our mechanical designers) that it was physically impractical to link the two pushers mechanically, thus the two servos. It was also impractical to attach our normal encoder to one side. Therefore we had to tap from the linking command signal which was fixed as a differential signal. Thus the interface.