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    I want to comunicate tow sureservo drivers model SVA 2100 to a BRX plc model BX-DM1E-18ED13-D also we Add a second serial port BX-PSER4-TERM
    need to set speed on bot servos and read the encoder counts , went the encoder reach a pre set count one of the servos need to run faster than the odeer to rip off a pre cut encolving film
    any examples on how to configuer ports on plc and send recive intructions
    any help is very appriciate

  • #2
    Are the servos in velocity mode? If so, you can set the first velocity parameter of both servo drives to the same thing, and then the servo you need to run faster can have a second parameter at the speed you want. Then when the BRX sees the encoder count is where you want, turn on an output that selects the alternate velocity for the one servo. Then set the velocity back down when you want it to.

    Another way would be to use high speed outputs on the BRX for both servos in a PT mode. Have the encoder velocity be manipulated however you want to reach the velocity you need. Copy that velocity into 2 tags/memory locations. Then when the encoder position is where it needs to be, use a multiplier on the second memory location velocity to increase it by a certain percentage. Your second servo will automatically increase speed since the running velocity move has a faster velocity now. Then you can remove the percentage increase whenever you need to. This way keeps the entire control within the BRX.
    Another way to do that would be instead of increasing the velocity of the second servo in the BRX, communicate a new, higher P1-44 value to the second servo when the speed needs to increase. Then send P1-44 back down to 1:1 when you need to speed to go back to equal.

    Or you can probably do the whole thing over RS485 modbus using one type of servo mode or another. On most machines I typically see things done over modbus type communication as it cuts down on cost of high speed modules, but since you only have 2 servos and the BRX already comes with more than 2 high speed outputs doing everything over modbus seems like a slow and cumbersome way to do it IMO.

    So there are a few ways to do whatever you need, how you do it is up to you. I would personally do all the control in the BRX, so that if I ever need to I also know the current position of each servo in the program. Whereas using velocity modes and switching with discrete IO the BRX wouldnt know where each servo actually is.
    Last edited by MikeN; 06-29-2018, 11:57 AM.