RSLogix 5000 Ladder Ramp Function

Good afternoon,

This is my first post with this website and I am also relatively new to ladder based programming (used mostly SAMA with DCS platforms).

Here's what I'm trying to do in ladder:

I have a pump and a discharge control valve (equipped with an I/P). When the pump is first started, the valve will be placed at 10% until pressure builds to 50 psig. At this point, the valve will be slowly ramped from 10% to 100% over 30 seconds. PID function is not required for this valve at all.

I've attached a screen shot of my software. The problem is the CPT function only provides a result when TON is done. I need it to pass a value continuously over the course of 30s to ramp the valve. Any simpler way of doing this? Any help is greatly appreciated.

The image is a little blurry so correct me if I'm wrong.

This is your equation:

a) When you write numbers without decimals the controller will cast them as DINT. Also, HC_6108_Ramping_Up_Position is declared as DINT.

b) When the controller executes Timer.ACC/Timer.PRE, probably the result is being casted as DINT because the other parameters and the output variable are DINTs. Then you have two possible results: 0 and 1. You get 1 only when the timer is finished.

You can rewrite the equation like

a) I'm adding a ".0" to all the numbers. Now the numbers are casted as REALs.

b) Adding .1 to Timer.ACC is just a trick to tell to the controller "cast this division as REAL". Since the range of Timer.ACC is so big, adding 0.1 won't be significant.

Other way to get the same result is:

You can add some logic to keep the value equals to 100 is the result of the equation is greater than 100.

The picture attached is not clear
You can try this:
(Timer.ACC/Timer.PRE)*90 +10

nhatsen you are exactly correct. Thank you so much for the help.