Ramp up analog output with ladder Rockwell Studio 5000

[josumaru]

Hello! Hope you are great. I need to make a change in a PLC with ladder logic. I will mount a analog valve and I need to control it in ramp up control. Basically en 10 seconds the analog output should be 10% 4-20mA (this is the maximum). And ever 1 second should ramp up 1%, to closet should be more fast, also with timers. Anyone can share the most efficient ladder logic to do it? I was thinking with timers and MOV fuction, with comparers. Less and GTR.

In function block we have the RMPS but not in logic. Thank you buddies!
Greetings,

 

[idiotsecant]

so you know your output must range from 4 to 20, and your ramp timer ranges from 0 to 160(S), right? So there is a formula you can multiply a timer.ACC by in order to produce a proportional value somewhere between 4 and 20, right?

 

[josumaru]

Yes. The analog output can be a variable, I put a example of 10%. I want to ramp up until X% (4-20mA) in X seconds. I can scalate the timer to the analog output. But im looking for a good ladder logic, also I can use timer.tt until get the acc to ramp up.

 

[JunQ]

An edge per second plus a CTU(ramp up) would be suitable for you. Preset = 100 let you scale 0-100 to 4-20mA and .ACC is current open%. At the same time, a CTD, preset = 100 as well, will let you close the value from open position. In the ladder, toggle Start bit to pause/continue the ramps so you can have a chance to maintain the opening under whatever condition you want.

 

[OkiePC]

I've done this a few times over the years as far back as my PLC-5 days. What I found most straightforward was to use a timer and load its preset with the desired ramp time. Next, calculate a Real number as the timer.acc/timer.pre. Be sure to clamp the result between 0.0 and 1.0 because the timer.acc can overrun the pre by a few counts. Then multiply that scale factor by your top-of-ramp output tag and send it to the target address.

 

[Rob...]

Instead of a timer you could use a timed task, and just add/subtract an amount calculated based on the cycle time of the task.

 

[MarkNightingale]

Hi,

I have attached an AOI that I use exactly for this function.

It is attached as a zip file. Download it, and then rename it to a .L5X file and import it into your software. Its pretty self explanatory how it works.

Let me know if you need any help understanding it.

Cheers

Mark

 

[josumaru]

Thank you all, the real MVP.