Micro 1400

[jd_hartzell 0]

Ok guys I have a project was wondering if some one could help me out. I am programming a hydraulic press and I need a ramp over time program that is close loop so I want to wait until the press has stopped moving at a low pressure then at that point take over and ramp say 100 tons to 1000tons over 3 secs while monitoring the pressure transducer I have a prop relief valve to do this everything is 0-10vdc where do I start will the PID function in the RS500 work? if so can some one do an example? or is this the way to go Help!!

[PLCMentor.com 60]

Ok you mention that your ramp needs to be closed loop. I think what you are saying is that you need to control the pressure closed loop (thus the PID) and then you need to ramp that pressure from 100 to 1000 psi. In thinking about this, you need to separate the two tasks. You have a need to control the pressure and the PID instruction is the best means in which to do this. Then you need to ramp the SETPOINT of the PID from 100 to 1000. During the ramp your PID will work to maintain the feedback pressure at the setpoint required. You can ramp the setpoint by simply adding to it a controlled amount controlled by a timer or an STI (timed interrupt) routine. There is also a ramp instruction (RMP), but I have never used it. It may be a little overkill for your requirements. Now if you had a linear response on your output and input I would just ramp your output signal and do without the PID to simplify things. I suspect from your post that you need to control your pressure as there are factors that can cause the pressure to be different at a set output.