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  • jayjohnsonuga
    started a topic Click PLC Will Not Communicate Across Data Tap

    Click PLC Will Not Communicate Across Data Tap

    The scenario is we have a bar code scanner, Click PLC(c0-00dd2-d), wireless serial device server, and cnc control. The wireless serial device server has two serial ports. One is used for communication with the cnc control. The other is used for communication with the Click PLC and bar code scanner. The bar code scanner and Click PLC are connected with a data tap. Now I have wired the connections for the PLC and bar code scanner to use different sets of pins so that the devices can't interfere with each other and wired the out on the tap to combine the transmit pins.

    The problem I have run into is when both the bar code scanner and the Click PLC are connected to the tap only the bar code scanner communications are received. The Click PLC shows that it is transmitting but nothing is ever received by the wireless serial device server. I have tried switching the devices around to verify that both ends of the tap work. Also I have tried only connecting the Click PLC to see what happens and it works when it is connected by itself from both ends of the tap.

    So what I can't figure out is why the Click PLC communications do not get through when both devices are connected. Any suggestions would be much appreciated.

    I could switch to using a modem data splitter, but those cost twice as much.

  • jayjohnsonuga
    replied
    Originally posted by Tinker View Post
    What serial device server are you using? I found a Moxa NPort W2250 at just about your price, and it does "RS-232/422/485", I don't know which model of CLICK you are using, but if you have one with RS485, you might consider having the barcode reader talk to the CLICK and have the CLICK re-transmit that data and its own data to the device server via RS485. That way only one device is talking to that port on the device server. However, I'm not sure reciving the barcode data intothe CLICK is going to be all that easy
    I figured out how to get the Click to receive the bar code scanner's output and retransmit. If anyone is interested in seeing how I did it. I can send you the ladder from the Click and an explanation of how I did the wiring.

    Leave a comment:


  • jayjohnsonuga
    replied
    Originally posted by scott.lawrence View Post
    EP-COM-008 Ladder example for receiving ASCII input. Typical application would be a bar code scanner or weight scale that sends data to the PLC and does not require any communication from the PLC


    http://support.automationdirect.com/examples.html#com

    Thanks. I will take a look and see if I can figure it out.

    Leave a comment:


  • scott.lawrence
    replied
    EP-COM-008 Ladder example for receiving ASCII input. Typical application would be a bar code scanner or weight scale that sends data to the PLC and does not require any communication from the PLC


    http://support.automationdirect.com/examples.html#com

    Leave a comment:


  • jayjohnsonuga
    replied
    I think I have found the issue. Voltage on the Click transmit pin is -5.5. Voltage on the bar code scanner transmit pin is 4.6. So I'm guessing this voltage mismatch is causing the issue???

    Now I have something I can show the bean counters explaining why we need to get the modem data splitter.

    Also going to try Tinker's idea of connecting the bar code scanner to the Click. Any suggestions on what to put in the ladder to receive the info from the bar code scanner?

    Leave a comment:


  • Do-more PE
    replied
    Yes. RS-232 is very voltage and ground sensitive.

    Leave a comment:


  • jayjohnsonuga
    replied
    I've got a new thought after reading more about rs232 communications. Could the problem be that the bar code scanner is using one voltage and the Click a different voltage? Would that cause an issue?

    Leave a comment:


  • jayjohnsonuga
    replied
    Originally posted by Tinker View Post
    True enough, but that is not what you are trying to do. You want two devices to talk to (one way) to your serial device server, which means both transmiters (bar code reader and CLICK) are conected to the one recive line of the server, with bipolar RS232 that is not permisible.

    Well, BlackBox says: "All nine pins are wired straight through", so there is nothing stopping data from coming out and causing the two RS232 signals to fight with each other. While you are using different pins on the input of the tap, you jumpered them togeter at the output, so the two transmit lines are connected together.

    What serial device server are you using? I found a Moxa NPort W2250 at just about your price, and it does "RS-232/422/485", I don't know which model of CLICK you are using, but if you have one with RS485, you might consider having the barcode reader talk to the CLICK and have the CLICK re-transmit that data and its own data to the device server via RS485. That way only one device is talking to that port on the device server. However, I'm not sure reciving the barcode data intothe CLICK is going to be all that easy


    I am using the NPort W2250A. I have done a new test. Two Clicks using the data tap and that worked. Then tried two bar code scanners and that worked. Any new thoughts?
    Using Click c0-00dd2-d only has two ports and one is for programming only.
    Last edited by jayjohnsonuga; 12-13-2013, 09:07 AM.

    Leave a comment:


  • plcnut
    replied
    Tinker may have mentioned a solution that would work for you:

    Txd from the Barcode scanner to Rxd of CLICK.
    Txd from CLICK to Rxd of your serial server.

    If you can stream the data from the bar-code scanner into the CLICK and then send it right back out of the CLICK to the Server, then that may be your best option.

    NOTE: I have very limited experience with the CLICK, and have never attempted data handling with one.

    Leave a comment:


  • Tinker
    replied
    Originally posted by jayjohnsonuga View Post
    The tap allows one device to listen to whatever communications are going on between two devices.
    True enough, but that is not what you are trying to do. You want two devices to talk to (one way) to your serial device server, which means both transmiters (bar code reader and CLICK) are conected to the one recive line of the server, with bipolar RS232 that is not permisible.

    Data can't go back through the tap, data only comes out. Which is fine for what I want.
    Well, BlackBox says: "All nine pins are wired straight through", so there is nothing stopping data from coming out and causing the two RS232 signals to fight with each other. While you are using different pins on the input of the tap, you jumpered them togeter at the output, so the two transmit lines are connected together.

    What serial device server are you using? I found a Moxa NPort W2250 at just about your price, and it does "RS-232/422/485", I don't know which model of CLICK you are using, but if you have one with RS485, you might consider having the barcode reader talk to the CLICK and have the CLICK re-transmit that data and its own data to the device server via RS485. That way only one device is talking to that port on the device server. However, I'm not sure reciving the barcode data intothe CLICK is going to be all that easy

    Leave a comment:


  • jayjohnsonuga
    replied
    Originally posted by bcarlton View Post
    Or... add another wireless serial device server to give each device its own port.
    Can't do it. Too expensive. I have to duplicate this 50 more times. So sure if this was the only machine I had to do then yeah just buy another wireless device. $312.50 for a wireless serial device server or $27 for data tap. Budget is $450 a machine. Plus there are other things I need like wire, cat 5 cable, db9 modular adapters, dc to dc converter to go from 24v to 5v.

    I could use a modem data splitter, but it's $61.50. Which would put me over by $20. So if I can't get the data tap to work I may just not be able to do all 50 machines.

    Leave a comment:


  • jayjohnsonuga
    replied
    Tinker,

    The tap allows one device to listen to whatever communications are going on between two devices. Data can't go back through the tap, data only comes out. Which is fine for what I want.

    Leave a comment:


  • bcarlton
    replied
    Or... add another wireless serial device server to give each device its own port.

    Leave a comment:


  • Tinker
    replied
    Originally posted by scott.lawrence View Post
    the tap you linked to is a tap... i,e, it will allow you to parallel data flow to a monitoring device. It's not a splitter...

    Originally posted by jayjohnsonuga View Post
    scott.lawrence that is exactly what I want to do. I want to get data from two devices on one serial port. Data only goes from the devices to the port. I wired the two devices on separate sets of pins then combined them on the other side of the tap. This should allow both devices to use the same port without interfering with each other on the other side.

    However, only one devices communications are getting through when both are connected to the tap.
    While it might sem like that "is exactly what [you] want to do" it is actualy the oposite, the tap is to get data from one device to two devices. You want to go from 2 devices to 1 device, not easy to do with the (officialy) bipolar RS232 signals, many devices will work with a unipolar version ofthe signal, and the diodes Scott sugested might work, but if your bar code reader is keeping its optput high, even a diode won't help, still it could be worth a try.

    Another posibility would be to use a realy to select which signal is going to be sent to the wireless thing, since the CLICK is a PLC it can easily control a relay. You'd want to leave the barcode reader normaly connected, and the CLICK would switch the relay only when it was sending data.

    Leave a comment:


  • plcnut
    replied
    According to the site, all pins are wired straight through, with a side tap for a scope/listening device. As near as I can tell it is tying both Tx's to the Rx. Add a diode inline with each Tx line and it may work.

    Leave a comment:

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