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jnordhag
February 12th, 2006, 10:41 PM
I am a Mechanical Engineering student working on a Senior Design project that is over my head, please help.



I have a Twido PLC which needs to communicate with the controller from a light-curtain sensor. The controller will output either an RS232 or RS485 signal in ASCII format, and the PLC has an RS485 port. Is either of these easier or preferable to work with from the PLC end of things? What do I need to do in the PLC programming to receive the signal from the light-curtain controller? I don't know how to get this into my ladder program, or what to do with it once it is there. Any help on this topic would be very much appreciated.

Thanks,
Jon
CaseyK
February 12th, 2006, 11:39 PM
Check your light curtain for a NO or NC (normally open or normally closed) contact, that can be wired directly into one of the Twido inputs.

Serial communication, if in fact it is posible, will probably be difficult, at best.

regards.....kc
jjvijay
February 13th, 2006, 01:36 AM
WHAT FOR U ARE USING SERIAL COMM BETWEEN CONTROLER WITH plc
jnordhag
February 13th, 2006, 11:46 AM
The light-curtain is made up of 128 separate beams. The controller can output exactly which beams are broken and which are not, but it is in the form of an ASCII serial signal. We need this information as an input to the PLC.

Jon
10baseT
February 13th, 2006, 11:59 AM
If you do that (serial coms) , by definition , then you won't be using the light barrier as part of a safety dependent process .

These comms are not generally used in the way you imply -
jnordhag
February 15th, 2006, 12:26 AM
The light-curtain is used to detect width and position of an object; it is not being used as a safety device like most are. From my understanding, the serial port is normally used to connect and communicate with slave PLCs. I thought that it might be possible to set up the light-curtain controller as a slave to the Twido PLC, but I don't know if this will work, or how to do this. It is not a common on/off input; it is a serial signal which I haven't found much information on. I have read some about saving the signal into the memory in the PLC and then calling it out in the ladder program. Is this a possible approach? I really don't have a understanding of how this connection works and am searching for any help possible.



Thanks for the replies,

Jon