jimbom
Member
gentlemen,
I have been programming plcs for 15 years but almost exclusively discrete i/o. Recently, I took on a project with both analog and discrtet i/o. The system is comprised of a slc5/05 processor with digital and analog modules. I control a hydraulic cylinder with a linear transducer for feedback with a proportional valve. PV is 4-20ma and CV is -+10v. I have the PID loop working properly with target sp set by a button on an HMI. It extends when hit the + button and retracts when you hit the - button. The problem is that in auto mode the operator controls the cylinder but on occassion the operator will take the system out of auto mode and put it into manual mode. At this time he will move the cylinder manually with a selector switch. Since the PID loop is still functioning it will try to move the cylinder back to its last setpoint position. Is there any way to turn off the PID function at this time? Disable the output channel? or in manual move the linear transducer value into the setpoint value? Any input (pun) would be greatly appreciated.
Thanks
Jim
I have been programming plcs for 15 years but almost exclusively discrete i/o. Recently, I took on a project with both analog and discrtet i/o. The system is comprised of a slc5/05 processor with digital and analog modules. I control a hydraulic cylinder with a linear transducer for feedback with a proportional valve. PV is 4-20ma and CV is -+10v. I have the PID loop working properly with target sp set by a button on an HMI. It extends when hit the + button and retracts when you hit the - button. The problem is that in auto mode the operator controls the cylinder but on occassion the operator will take the system out of auto mode and put it into manual mode. At this time he will move the cylinder manually with a selector switch. Since the PID loop is still functioning it will try to move the cylinder back to its last setpoint position. Is there any way to turn off the PID function at this time? Disable the output channel? or in manual move the linear transducer value into the setpoint value? Any input (pun) would be greatly appreciated.
Thanks
Jim