1400 with 1762-IF4 AI card

[Bryan Whitfield 0]

Hello,

I have a 1400 with a 1762-IF4 analog input card.  

I am using a LVDT for positioning on a hydraulic cylinder.  

The LVDT is reading fine and resolution is good.

Input configured for 0-10, no problems there.

I have the AI Channel filter set to " None, 130 ms update" ( lowest setting)

MY PROBLEM:

I need to stop the cylinder on a dime with dependable repeatability.  Not getting that result.

I am currently of the troubleshooting opinion that the AI is too slow for what I'm trying to do (Remember-Filter at "None, 130 ms update")( or, am I misinterpreting the 130 ms) 

I have this exact same LVDT in other applications with other AB PLCs, ( all be it, newer ones) with profound accuracy.  

Does anyone know of a corner I'm not looking into?

Please help.  Factory Acceptance Test tomorrow!!! Doesn't look like I'm gonna make it.

 

Thanks,

Bryan Whitfield

 

[TimWilborne 108]

What are the "newer" PLCs that you've successfully done this on?

[Bryan Whitfield 0]

CompactLogix 5343

[pturmel 157]

1 hour ago, Bryan Whitfield said:

I have the AI Channel filter set to " None, 130 ms update" ( lowest setting)

Yup, terribly slow.  A 1400 is just not a fast platform, and limits like this highlight that.

The best you can do is a two-stage approach to the target.  Trigger decel early to a creep speed, then stop from creep.  The creep speed would be chosen to yield the desired target tolerance with a latency of (130ms + scan time).

[Bryan Whitfield 0]

Thanks Pturmel and Tim,

You have confirmed my thoughts.  I'm digging through dusty shelves all over the country trying to find a PLC I can go pick up.  

Many Thanks,,,,and Tim, I really enjoy your YouTubes, they've bailed me out more than once.  I was shocked when I saw you pop up in a reply.  

If anybody thinks of a miracle, please post back.

 

Thanks to all

Bryan

[TimWilborne 108]

One other thought, does the 1400 have built in analog inputs?  I wonder what their update rate is.  Glad you like our videos!

[pturmel 157]

If you can't find a suitable PLC quickly, you might consider putting an external hydraulic controller between the 1400 and your device.  I've had good results with Delta's products in the past.  They support AB's SLC/PLC-5 register-style messaging.

{ Maybe not.  Brutal pricing. }

[Bryan Whitfield 0]

Tim,  unfortunately not, on the onboard AI.

Pturmel, lol on the brutal pricing.  

I'm making my rounds with our sister sites to see if I can borrow a 5343 and rack and cards long enough for the test. I found one in Tampa, be driving all day and night to get.  

Again,  Many, Many Thanks,

Bryan