RSlogix500 help

hi all, im new here and im a student of auckland university, new zealand. I am doing a motor position control project using Rslogix500.

THE Project:- to control 3 motors (accuracy is 1 degree) using the PLC. and also to take an analog input from a photodiode , convert it to digital (ADC) and store the digital info on the plc.

Why am i here:- this is my first time with PLC, just started to learn the basics. Can someone help me with how i can get the plc to control the motors individually to 1 degree accuracy and how do i use the ADC on the plc. I have started a ladder logic on the software but i cnt get the hang of how to get the servo motors to spin to the 1 degree accuracy.

If you have rslogix software and have done similar sort of project then i woud defintly want to have a look at the ladder logic.

all help is appreciated

thankyou

There are likely one or two of us here more than willing to help, but the more details you feed us the better. First up we will need to know more about the hardware setup you are using.

I'm based here in Wellington and there are one or two other kiwis around as well. Welcome aboard PLCs.net.

hi philip,. its great to hear from ya.
Wel at the moment the only thing i have is the software logix500 with rslinx and the plc which i have to program. The choice of motor is up to me as this is for a project and the motor to use will most likely be on of the allen bradley servos.
Motor one should be able to move all 360degree and the other two motors only need to move 180degrees.

The entire project is to allow a user to input their choice of increments through the 180 or 360degree range of angle
e.g. move motor 1 from 0deg to 60deg in 1deg increment and from 61deg to 150 in 5deg increment and so so on. This is for a photometric measurment purpose and at each increment the photodiode will measure a luminares light intensity in analog then send it to PLC which will convert it to digital and then store it in a table so that it may be plotted in graphical form on a pc.

so there u have it, I have a brief on this if u want i can email that to you.

Can we clarify what the catalog numbers are for the hardware. AB has made quite a few PLC's over the years and we need to know what family we are dealing with. We are looking for numbers like:

1747-Lxxx for the SLC500 processors

or

1756-Lxx for ControlLogix,

plus what chassis and I/O you have.

Is the software RSLogix500 or RSLogix5000? (Makes quite a bit of difference.)

sorry. Its micrologix 1500, , Rs logix 500 and Rs links, connecting throught the Rs-232 serialcom port 2.
The I/O config is read off the logix1500, and is, AD_DF1-1 Node 1d local.
Advanced I/O modules, Word 0 is enable- output range 0 to +10vDC and Word1 is enable - output range 4 to 20mA.

These are all the config that i need to setup the micrologix1500 to software logix500 through rslinkx.

With this hardware your options for true servo control are going to be limited.

The main problem will be that the analog inputs are going to be rather too slow for fast stable position control.

The next key piece of info is to establish how fast you need to make the moves that you have described. The faster they are the more demanding it will be.

Fusion, with this hardware option I recommend that you plan on adding a DeviceNet card to the ML1500 and use an Ultra3000I drive w/ DNet interface. Get a drive with the I suffix - its an indexing drvie. You can then send the drive a position command over the devicenet from the PLC - and it will handle all the rest - no need to program the motor control loop, just the position commands.

Alaric said:

Fusion, with this hardware option I recommend that you plan on adding a DeviceNet card to the ML1500 and use an Ultra3000I drive w/ DNet interface. Get a drive with the I suffix - its an indexing drvie. You can then send the drive a position command over the devicenet from the PLC - and it will handle all the rest - no need to program the motor control loop, just the position commands.

Click to expand...

Wouldn't this require RSNetworx for devicenet as well?
This sounds like the easy (but very expensive) way to go, but I have a feeling that's not what the poster was looking for.

hi, thanks for your posts, as above , will i need RSNetworx to connect it all up with the DeviceNet card. i am on a prety small budget of $400bux and with that i can hardly get the motors let alone buy more software from AB.

The other way i thought possible would be to Use C++ programming and use the PLC as a dummy device to accept 1 command at a time, do it, then send a reply to C++ says its complete and take a new command.
eg, istead of runnin the motor all the way with many increments, the software will only send one command, say we want to move the motor from 0 to 30 in 5degree increment..it will work like this- C+ tels plc to move motor from from 0 to 5, once this step it done by plc it will reply and say, that done, whts next, then the C+ will say now move from 5 to 10 and so on ...

This may not be the right thing, im still trying to figure out a way. wht do you guys think?

PhilipW said:

With this hardware your options for true servo control are going to be limited.

The main problem will be that the analog inputs are going to be rather too slow for fast stable position control.

The next key piece of info is to establish how fast you need to make the moves that you have described. The faster they are the more demanding it will be.

Click to expand...

the speed of the system has to be a bit slow, as it is going to be used in a dark room to measure light intensity at different angles. the photodiode will be taking the reading and it needs at least a 2 second wait before taking another measurment for good results. so i think about a 5 second delay is still ok as long as the job is done right, the speed isnt a major issue.