germ Posted January 21, 2011 Report Share Posted January 21, 2011 Hello, I have an optical position encoder (actually three of them, one for each axis) that transmits electric signals according to RS-422 standard. There are two quadrature channels (A and B) and a reference/stop channel. How to read this in LabVIEW? There is an expensive NI solution: the NI cFP-QUAD-510 4-Axis, Quadrature Encoder Input Module for Compact FieldPoint. This also requires a chassis and LabVIEW RT, which we don't have. Seems like overkill to me. There are third-party multi-axis RS422 counters with, say, an USB interface like this one: http://accesio.com/go.cgi?p=../usb/usb-ctr-15.html Unfortunately this one won't work, because it can't read quadrature signals. Actually having an added display would be nice. So what I am looking for is a box which accepts 3 or 4 RS-422 inputs and has a display for the counter and a USB, Ethernet, or serial interface from where I can get my position. Any suggestions? Quote Link to comment
ShaunR Posted January 21, 2011 Report Share Posted January 21, 2011 Hello, I have an optical position encoder (actually three of them, one for each axis) that transmits electric signals according to RS-422 standard. There are two quadrature channels (A and B) and a reference/stop channel. How to read this in LabVIEW? There is an expensive NI solution: the NI cFP-QUAD-510 4-Axis, Quadrature Encoder Input Module for Compact FieldPoint. This also requires a chassis and LabVIEW RT, which we don't have. Seems like overkill to me. There are third-party multi-axis RS422 counters with, say, an USB interface like this one: http://accesio.com/g...usb-ctr-15.html Unfortunately this one won't work, because it can't read quadrature signals. Actually having an added display would be nice. So what I am looking for is a box which accepts 3 or 4 RS-422 inputs and has a display for the counter and a USB, Ethernet, or serial interface from where I can get my position. Any suggestions? RS422 is multi-drop and can be cabled for distances up to about 100meters.. You can have all your devices hanging off of one RS422 port (up to 12 or 16 if memory serves). If you can get all your devices with a RS422 interface then you won't need to mix and match with USB. Make sure, however, that the devices are really RS422 compliant. Some manufacturers say that they are 422 when really they are point-to-point but with RS422 line drivers (i.e not addressable). I highly recommend the NI RS422/485 cards. for the PC end. Quote Link to comment
Grampa_of_Oliva_n_Eden Posted January 21, 2011 Report Share Posted January 21, 2011 RS422 is multi-drop and can be cabled for distances up to about 100meters.. You can have all your devices hanging off of one RS422 port (up to 12 or 16 if memory serves). If you can get all your devices with a RS422 interface then you won't need to mix and match with USB. Make sure, however, that the devices are really RS422 compliant. Some manufacturers say that they are 422 when really they are point-to-point but with RS422 line drivers (i.e not addressable). I highly recommend the NI RS422/485 cards. for the PC end. I have also had succes with both the USB and ethernet versions of NI's adapters. Ben Quote Link to comment
germ Posted January 21, 2011 Author Report Share Posted January 21, 2011 RS422 is multi-drop and can be cabled for distances up to about 100meters.. You can have all your devices hanging off of one RS422 port (up to 12 or 16 if memory serves). If you can get all your devices with a RS422 interface then you won't need to mix and match with USB. Make sure, however, that the devices are really RS422 compliant. Some manufacturers say that they are 422 when really they are point-to-point but with RS422 line drivers (i.e not addressable). I highly recommend the NI RS422/485 cards. for the PC end. ShaunR, those are serial interface cards. It is not clear to me that they will work for my purpose: The encoder emits quadrature pulses through the serial interface, but I need a COUNTER to read the position, then poll it from the PC. I don't think a simple serial interface card will do this. Quote Link to comment
Grampa_of_Oliva_n_Eden Posted January 21, 2011 Report Share Posted January 21, 2011 ShaunR, those are serial interface cards. It is not clear to me that they will work for my purpose: The encoder emits quadrature pulses through the serial interface, but I need a COUNTER to read the position, then poll it from the PC. I don't think a simple serial interface card will do this. Well you did ask about rs-422... You aaperently are asking about EIA-422 which just desries the electrical charateristics of the wire and associated ciruitry. You maybe able to use an RS-232 reapeter that use EIA-422. I'd look at Black Box or the like. Ben Quote Link to comment
ShaunR Posted January 21, 2011 Report Share Posted January 21, 2011 ShaunR, those are serial interface cards. It is not clear to me that they will work for my purpose: The encoder emits quadrature pulses through the serial interface, but I need a COUNTER to read the position, then poll it from the PC. I don't think a simple serial interface card will do this. Well. NI also do counter timers. But it is's really a sledge hammer to crack a nut. Whenever I come across devices like I think you are describing, I always use a PIC to convert whatever in to RS485 and have a nice serial ascii value returned (you can even do stuff like streaming to the PC). Cost less than $5 a throw, much more reliable and has a huge saving on cabling in multi-device environments. And once you've done it once, you can use it on virtually any obnoxious interfaces with a bit of software tweaking. Quote Link to comment
germ Posted January 22, 2011 Author Report Share Posted January 22, 2011 Well you did ask about rs-422... Well, yes, but I also explained (obviously not clearly enough) my situation. You aaperently are asking about EIA-422 which just desries the electrical charateristics of the wire and associated ciruitry. Sorry, but the documentation that comes with the positioner clearly states RS-422. You maybe able to use an RS-232 reapeter that use EIA-422. I'd look at Black Box or the like. Ben No idea what you are talking about. Well. NI also do counter timers. But it is's really a sledge hammer to crack a nut. Whenever I come across devices like I think you are describing, I always use a PIC to convert whatever in to RS485 and have a nice serial ascii value returned (you can even do stuff like streaming to the PC). Cost less than $5 a throw, much more reliable and has a huge saving on cabling in multi-device environments. And once you've done it once, you can use it on virtually any obnoxious interfaces with a bit of software tweaking. Hmmm....a PIC.....what is that? Maybe this? http://en.wikipedia....microcontroller I am asking for a finished solution, a box that I can buy. Not a chip or something where I have to spend a month building something around it... Quote Link to comment
ShaunR Posted January 22, 2011 Report Share Posted January 22, 2011 (edited) Deleted 'cos can't be bothered. Edited January 22, 2011 by ShaunR 1 Quote Link to comment
jdunham Posted January 25, 2011 Report Share Posted January 25, 2011 ShaunR, those are serial interface cards. It is not clear to me that they will work for my purpose: The encoder emits quadrature pulses through the serial interface, but I need a COUNTER to read the position, then poll it from the PC. I don't think a simple serial interface card will do this. So wait, why aren't you using an NI Counter/Timer card? They are awesome at this. Each encoder should be able to use one of the counters, and the other quadrature channel typically goes into the digital I/O port. Your local NI sales can usually do a much better job than I can of walking you through the nitty gritty of picking the right card and connectors. You may need a 422-TTL level shifter IC. You can either get one for $1.50 from digikey or if you are allergic to chips, you can get one packaged in a $45 device from B&B electronics, and get another $20 of connectors to make it work with your breakout box. Quote Link to comment
germ Posted January 27, 2011 Author Report Share Posted January 27, 2011 So wait, why aren't you using an NI Counter/Timer card? They are awesome at this. Each encoder should be able to use one of the counters, and the other quadrature channel typically goes into the digital I/O port. Your local NI sales can usually do a much better job than I can of walking you through the nitty gritty of picking the right card and connectors. You may need a 422-TTL level shifter IC. You can either get one for $1.50 from digikey or if you are allergic to chips, you can get one packaged in a $45 device from B&B electronics, and get another $20 of connectors to make it work with your breakout box. jdunham, thanks for your reply. I am aware of the $$ NI option. Now we have bought those: Counter to USB converter Hopefully they will work.... Quote Link to comment
jdunham Posted January 27, 2011 Report Share Posted January 27, 2011 jdunham, thanks for your reply. I am aware of the $ NI option. Now we have bought those: Counter to USB converter Hopefully they will work.... Well that does look like a pretty sweet device. However, you're going to need three of them and a USB hub, so that's about $200, and you could have bought an NI 6601 ($400) , a $60 ribbon cable, and a cheap connector block from http://www.daqstuff.com/68_pin_daq.htm and be off to the races. That's a little more money, but you wouldn't have to write your own labview drivers for the device. Of course you'd still have to wire up your own differential level shifter chip, so you may have done the right thing after all. The NI should have much higher data rates but that may not be important for your project. Anyway, good luck with it. Quote Link to comment
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