PLC to Control Board

Discussion in 'The Projects Forum' started by roro36, Dec 9, 2010.

  1. roro36

    Thread Starter Member

    Sep 7, 2010
    I have a control board that uses a 10K pot as a power setting. The system is moving to a more PLC based one and I want to remove the manual pot for someting controllable via the plc. However, it should still be able to be controlled manually. I looked at a motorised pot, but they seem hard to get, so I looked at a digital pot. This seems like a good enough solution, but still problamatic as the inputs are limited to 5V. So i thought that beacuse the system is alreafy going to have a plc, I could use that?

    By having buttons for up and down connected to the plc and then a digital to analogue expansion card to give the reference voltage that the card is looking for across the pot. The problem, i think, would be to interface the refernce voltages between the 2 boards. The board in the machine will have its own power supply and is currently sending 0 and 10V to the pot, and the reference signal is then fed back into the board. Now would it be possible to use a plc with an expansion card? Can the expansion card be tied to the same ground as the control board to allow foe an output dc voltage to be read by the control board based on the 2 buttons that we would control the up/down of the output voltage from the DAC?