PLC idea for freshman high school student (my daughter)

[TConnolly 13]

My daughter is in a 9th grade technology class at school. Apparently her teacher has an interest in PLCs but has never actually worked with one, but he has been itching for many years to have a student who can do a PLC project for their class project. He found out that I am a PLC programmer so now he is suggesting my daughter to do something with a PLC. I don't have a lot of equipment and don't particularly want to spend a lot of bucks but I do have a fixed SLC-500, a ML1K, and a really old GE Series One with a hand held programmer. I have a handfull of push buttons, a limit switch, a few 24v valves and some Bimba pencil air cylinders, a water bed pump and a photo-eye. Anyways, I'm looking for ideas for something simple that won't cost much in the way of new hardware and that would be easy to program. A light chaser would be cheap and simple but unfortunately, it's not cool enough to suit my daughter. All suggestions are welcome.

[BobLfoot 302]

If the 24V Valves will handle H2O and you have piping, using the water bed pump as the pressure generator for a water fountain display could be pretty cool. The bimbas could move the jets around and the valves turn jets on and off. The PE could trigger the whole thing to start when somebody walks by and the pushbuttons could select patterns. You might also tie in a cheap radio/cd player for music timed to your show. The SLC 500 can probably drive it all.

[TConnolly 13]

Not a bad idea Bob, but there is just one thing that is so very wrong with it. If my wife sees something that cool then I'll find myself in the yard with a shovel and one very large pile of rocks building a full sized version so fast I won't know what hit me. Edited 21 Nov 2006 by Alaric

[BobLfoot 302]

Surely you can convince her that full size with pricey industrial vavles is impractical.

[Crossbow 296]

You could always tell her that local zoning ordinances prevent the installation of anything cooler than a sprinkler unless you also plan to put one in front of the town hall. Residents are not allowed to have anything cooler than the municipality.

[Guest]

not sure if it would fit your budget, but several years ago I helped some high school students come up with a “robot movement” idea ... something like a “poor man’s feed screw” ... basically they took electric screwdrivers apart and mounted the “motor ends” onto pieces of “O-Strut/Kindorf” with hose clamps ... they replaced the screwdriver bits with 1/4-20 all-thread rods which ran the length of the O-strut ... we (well, actually I) used a table saw to whittle grooves into a 2X4 block - suitable for sliding back and forth along the strut ... we mounted a “nutplate” at the bottom end of the sliding block and ran the all-thread rod through the nutplate ... the PLC would energize either a “forward” relay or a “reversing” relay to run the screw back and forth along the strut ... the kids mounted limit switches along the strut as PLC inputs ... training idea: throughout all of this (except for the table saw part - for obvious safety reasons) I kept a strict “hands in my pockets” approach to the project ... specifically, I would allow myself to coach - and describe - and even to direct - but NOT to touch anything ... the kids were able to honestly say that they “built it” all themselves ...

[BobLfoot 302]

KEWL RON you topped mine

[TConnolly 13]

Ron, I like that idea, especially the idea of using electric screwdrivers. Safe. Cheap. Simple. Cool. Once again, I owe you one.