GPS cordinates into PLC

I'm developing a system for ships using a Schnieder Micro PLC and have been asked if it would be possible to connect it to a GPS receiver to get longditude and latitude cordinates. Any one done any thing like this before or point me to some info. I've got an extrex and was going to have a play with using RS232 instuctions to extract the cordinates from it.

US Navy developed using GPS and navigation for autopilot and positioning. Aircraft also.

May be easier to look for system already developed and on market ??

I would think by now local marine stores would have something - may not meet your accuracy or reliability standerds but you don't know til you check.

Dan Bentler

Check out http://www.boondog.com/%5Ctutorials%5Cgps%5Cgps.html for info

Ask your Schnieder rep if they offer a GPS module for that particular PLC. Siemens (S7) and AB (ControLogix) offer one used to time-stamp S.O.E. (sequence-of-events) recording for utilities.

http://www.hiprom.com/Products/1769hpGPS/1769hpGPS.htm

This site has a GPS card for the Controllogix Platform, with Rockwell. You would have to change out the plc, but it has everything you need.

The keyword is NMEA0183. Google it, it's a simple ASCII protocol used by GPS and other marine equipments.

You have to write a PLC program that from the incoming ASCII string:
- pick out the right sentence
- pick out the right field(s) and it's contents
- convert row(s) of letters to a number e.g. "1" "0" "5" "." "4" -> 105.4


Be also aware of that even if NMEA0183 define the electrical interface to comply with EIA-422 you will also find talker output with RS232 or a quasi 5V relative to ground that is not a differential system. An example of the last one is GPS from Simrad.

The "advantage" with the 5V relative to ground signal, is that even if it is outside both the RS232 and the RS422/485 standard, it was possible to connect it to them all! Well, at least with the PLC I used.