obvious newbie, have questions!

stasis

Member
Join Date
Mar 2005
Location
Columbus, Ga
Posts
344
ok...first, some background. I work as an electrician/troubleshooter in an industrial plant that makes corrugated paper (no names, please). I've used PLC's for troubleshooting, editing, etc., but have only written programs using PicoSoft Pro & Moeller Easy software. Our 'tech' guy quit, and his duties have been thrust, much to my objections, upon me. Now I've been asked to write a program for a Micrologix controller for use as a jam detector.

ok, on to the questions...
1. Can anyone recommend a site that goes in-depth concerning integers (sp?), HSC, math & comparators?
2. Is there a way to simulate a program in RSLogix 500, like in the PicoSoft Pro?
3. Any tips about getting started with programming in general?
 
stasis,

Your questions, in order of importance:

(3). Tips to get started: Learn the correct way (as opposed to what 95% of PLC programmers do), and figure out what Outputs that you need for your jam detector. In other words, once it sees a jam, what does it need to do? (Turn on an Alarm bit? Stop the machine?) If you can figure out the output, you are nearly done! :D Listing the inputs to detect the jam is then a piece of cake.

(2) The LogixPRO simulator is available from The Learning Pit (mrplc.com) and allows simulation of RSLogix programs.

(1) This site, of course, offers all those things you mentioned. You should sign up for Phil Melore's newsletter, where a variety of subjects are covered periodically.

If you still need help, make a beginning, then ask more questions here. If you have an urgent situation, send me a private message, and I will give you personal help (for what it is worth!)
 
Last edited:
You may be able to pickup some info in the "Learn PLC's" button on top of the page.

I drew schematics a long time before I came across my first PLC. In fact, I went to the plant to draw schematics for a machine upgrade. When they found out I was an electrician, I was out on the machine tracing down the old wiring. Then I was drawing the new circuit, which wound up being almost identical to the ladder logic.

If you can find your way through a complicated schematic, you shouldn't have any trouble changing the "innards" of it, to the corresponding ladder logic needed.

I learned math functions and blocks out of the manual "on the floor" while several managers stood over me waiting for startup. They are more intimidating, then anything.

regards.....casey
 
well, I wrote the program out in Pico, but found that even with the GFX controllers, the option for a HSC isn't fast enough. And there is no 'compare' block in standard Picos.

There is currenty an antiquated system in place that uses printed circuit boards for operation...three PE's (photo eyes) mounted along the product flow...if the second PE doesn't see the first PE's input in x time, a jam is determined. There is a prox mounted on a shaft used as a motion detector/pulse counter. Jam detection doesn't begin until x pulses per second are measured on the prox. This prevents false jams until run speed is achieved. If a jam is detected, the machine E-stops.

The logic/circuitry seems elementary enough...if I was using relay hardwiring. However, as stated before, I'm completely new to programming.

Thanks for the replies!
 
stasis,

You need a MicroLogic program similar to the following. There are many ways to do this, but this might get you started.


| PE1 PE2 JAM |
| I:1/0 I:1/2 B3/0 |
|---+---| |----+---|/|----------( )----------|
| | | |
| | JAM | |
| | B3/0 | |
| +---| |---+ |
| |
| JAM JAM TIMER |
| B3/0 +---------+ |
|--------| |----------------| T4:1 |------|
| | | |
| +---------+ |
| |
| JAM TIMER EMERG STOP |
| T4:1/DN O:2/0 |
|--------| |---------------------( )---------|

 
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Greetings stasis,

if you have the MicroLogix (or a spare) and the RSLogix500 software already available, then set up a "test stand" on your desk and start experimenting ... you can use spare sensors or just small switches from Radio Shack, etc. to simulate the field input devices ... you don't REALLY need output devices ... you can just watch the system's LEDs go off and on ... once you've started experimenting, then anything that's giving you trouble will become obvious ... you can post your program code here and we'll be glad to help you move forward ...

good luck ...
 
The logic/circuitry seems elementary enough...if I was using relay hardwiring.

Draw it that way. Forget Pico if going to use an ML, look at the instruction set in RSLogix500. Then put your hardwired relay into an ML program.
 

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