calculator progam

Oh given that age range you gotta keep it simple and therein lies the challenge.

By limit number entry to 3 do you mean 3 decimal places ie 1,000 (they will not grasp this large a number)
OR entering 3 different values ie 1 + 2 + 3.

I think you are going to have to rely on more graphics ie display both the number (assume 3) and some symbol say apples (3 of em)
Next line would be say two and would show two apples
Next line would be subtract yielding 1 and would show only one apple.

I think you would be a lot better off using a computer and some canned software designed to teaching kids. PLC is too "engineery" ?? to deal with kids their short attention spans, their need for both graphics and sound.

Dan Bentler

Yes, limiting the number is what I'd like to do. What I don't know is what box or coil to use to do it? What does that look like ladder logic? What variables are needed?

If you have more available inputs why not have the 3 number range as seperate buttons? then you would solve the multiple presses when each button is pressed have one assigned to values 1 2 3

You can't be serious...? RDRast is consistently knowledgeable, helpful, and professional and has been a productive member of this community for years.

Protiusmime said:

RDRAST:

If you think your arrogant, snide, and sarcastically rude reply is of any help to Parky or anyone else for that matter... please think again. I am sure Parky is hardly aware of the number of requests for homework help that comes across this forum from PLC students. Why then, would you treat them with such disdain? Are you trying to embarrass them into proper behavior so they never again "bother" you? Replies in these forums are by choice. Please choose to be a help and one who encourages (and patiently gives the correct example to) those who are just getting their feet wet. Keep the water clear instead of throwing up a stench. Believe me, your disdain far outweighs your demonstration of PLC knowledge, and even more, leaves a far worse lasting impression of disrespect for yourself.

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It's been awhile since I've used a DL, but I think you need to use a LDD before the ADDD and an OUTD after. As far as three button presses, you could use a counter with Preset=3 and ignore button presses after the counter is done.

For ADD I found they have something called an iBOX now and hope it works. Thanks for the counter idea, after a good nights rest I was thinking that was a solution and i will try that out...

I am a teacher and I can relate to students who won't think for their self and want everything to be easy. So I understand some forum members frustration. Some of my better students can code better than most engineers when they graduate. Some have never programmed before and don't know the difference between a nibble and a byte. I think a rpn calculator would be an excellent example for students to learn about arrays, push pull FIFO, math instructions, and basic data types in general. How would you build the keypad using only 4 inputs,4 outputs? They need the basics before they can track broken bottles down a queued coveyor, program a UPS or Amazon warehouse, control a temperature or level loop, configure a modbus interface,etc... Or even think about object oriented plc programs or state machines. Students can control a lot of equipment using ladder logic without ever fully understanding the data types that lay under the surface.

brooks, thanks for digging this thread. seriously.

Steve Bailey said:

Another hint:
When you finish this course, write a letter to whoever establishes the course content and ask them to revise it so that it uses real-world applications.
[snip]
Parky100, please know that I'm not criticizing you for your instructor's shortcomings.

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Yes, if my third grade teacher had had our class do 1-d <-> 2-d array translations using div and mod, I would have had a lifetime appreciation for 'remainder division!'