PLC and moving a Ram between two limit switches, and back via momentary switch.

[trellend]

I've got the ram moving forward to limit switch (based on physical user switch), then when switch is reversed, ram goes back to starting limit switch, as long as user holds in the switch.

[ ]-[/]-( ) Easy

I'd like to automate this so a momentary switch makes it latch, drive to limit, pause, then fire the other valve to bring it back to limit switch and stop.

I've seen how to latch

--------------[/Limit]--------------------(O)
| |
--[O]---------

I've been programming C/C++/C#/Pascal/ASM for ages, and I'm just trying to help some friends that have a dead machine. I went with the Click PLC, for cost. I've never done PLC, but have done quite a bit of micro controller work.

//Example if you wanted to scribble, or just plain comment about it is fine. I'm new to this.
X0 out limit
X1 in limit
X2 momentary user button
y0 Ram out
y1 Ram in

If anyone could explain the normal way this is done, I'd appreciate it.

I was thinking of just using a memory bit for each stage, switch sets bit (and master busy bit). Bit drives forward until limit, clears bit and sets new bit.
New bit triggers the reverse function to limit then clears bit and master busy bit.

Or is this typically done using a load of Or Not And logic only?

This is only the tip of the iceberg in this project, but if I can get some standard practices for readability, the rest is just more of the same.

Thanks

Charles

 

[IRstuff]

http://www.automationdirect.com/microsites/clickplcs/click-help/Content/177.htm

?

TTFN
faq731-376

Need help writing a question or understanding a reply? forum1529


Of course I can. I can do anything. I can do absolutely anything. I'm an expert!
There is a homework forum hosted by engineering.com:

http://www.engineering.com/AskForum/aff/32.aspx

 

[trellend]

Perfect, didn't find base index for that, but now that I know all that is there, I can find it. Exactly what I needed.

Has nice simple example programs showing logic control, flow for simple tasks.

Thanks a bunch,

Charles

 

[trellend]

LS = Limit Switch.
SW = Control Panel SW
O = Physical Coil/actual output.

I forgot to clear run, but does this seem logical? (unit is in the mail to me now, can't test)

Is this the general pattern for such a thing? Does have an error (like it will cycle over and over right now)....

 

[controlsdude]

When programming sets and reset or latch and unlatch, its best to program the set with all the states then the opposite program states for the reset. Otherwise your get a condition where it hangs in one state.

Also you cant have multiple output states for Accumulation Forward or back. What is going to happen is the PLC will just execute the last output of this Forward or Back. As it goes thru the logic.

Most PLCs do this

Looks at INputs
executes logic
sets outputs
repeat cycle

 

[trellend]

Are you saying I should

Set (forward, back), then just clear each bit as the task is completed?

 

[controlsdude]

Accumulation Forward or back should be an internal bit and use this bit for the output to go extend and restract. Well you can do both ways, try it and you will see what I mean. There are 1000s way to program, but you need to understand how a PLC works like I was trying to help you understand the way it scans inputs does the logic then turns on outputs, repeat.

 

[trellend]

All the C addresses are bits. Anyways, unit just showed up via Fedex, time to play.

Thanks for the tips/heads up/help.

I'll update post at the end of project with results/pics. This machine is over 100' long, 60' wide and 25' tall.

 

[trellend]

Here is a picture of the machine.

https://drive.google.com/file/d/0B882DaQ0eI-vTjN3eXVvYTdxWFU/view?usp=sharing

100' long is correct, maybe only 25' wide. Definitely 25' tall. I didn't measure because it's irrelevant.

 

[controlsdude]

Looks like fun! Hope your mechanical and electrical support is good otherwise i fail on stuff like this.

 

[trellend]

Got the parts Friday night, started tracing wires and cut out old series one controller Sat morning at 6am. Fully operational by 4pm Sunday. Smooth fast first PLC job.