Need help with reed sensor in ferris wheel

[Lancie1]

What I would like to see now is the program logic. What are you using to stop the wheel? It appears that you now have a motor with a brake.

Wow, what a mess of wiring! I guess they don't judge based on neatness and reliability anymore. It is all about flash and glitter. The real world will not be so easy.

...until all 8 chairs have been loaded/unloaded.

For all this time you have been saying 4 chairs. Why the deception? Did you expect saying 4 instead of 8 would lead to a more accurate program?

 

[Lancie1]

The most realistic part of your model is how it sways and flexs during each start and stop. Reminds me of those fly-by-night carnivals of my youth where you risked your life to get on one of the machines hauled in on a truck and set up with little regard for customer safety.

 

[oldskewl]

What I would like to see now is the program logic. What are you using to stop the wheel? It appears that you now have a motor with a brake.

Wow, what a mess of wiring! I guess they don't judge based on neatness and reliability anymore. It is all about flash and glitter. The real world will not be so easy.
For all this time you have been saying 4 chairs. Why the deception? Did you expect saying 4 instead of 8 would lead to a more accurate program?

I implemented 8 chairs at the last minute to help a little with the drift...no deception...to stop the chairs I had the motor do a reverse for .750 seconds- the motor is shot but it served it's purpose...concerning the wiring, it looked a lot worse at this point as I had already been graded and took it a part before I realized that I forgot to film it...so, I put it back together really quick and filmed for my own purposes!

Why all the hate Lancie1?!?!

 

[Lancie1]

No hate, just frustruation from yelling into a canyon with no echos.

...to stop the chairs I had the motor do a reverse for .750 seconds- the motor is shot but it served it's purpose.

Makes sense, a sacrificial method can do a job but not for long. I have done a few of those on real plants where there was some production deadline to be met, with time after to fix it right.

 

[OkiePC]

I think Lancie's frustration stems from the fact that we got little feedback from you after suggesting multiple methods to help.

If you had said why you didn't flesh out some of the ideas, he may have been able to overlook the wiring of a rookie

I was wondering what his complaints were while I waited for it to finally load. At the end when the camera finally showed more than 1/4 of the thing I saw what he was talking about.

As for the project, I think it is pretty decent overall on the surface, looks like a passing grade...not sure what the class...

Behind the curtain, however, it is obviously a piece of junk, which may satisfy its intents fully. Sorry, not trying to be cruel, but you said yourself the motor was cooked because of your design.

I was more worried about the things being said by the voices in the video, some of it I could not make out...overall the tone was one of luck and doubt...

Control engineers are never going to give you a thumbs up for something like that. Best I can say is "do better next time".

Don't be put off by criticism...use it.

 

[oldskewl]

Like I said...the wiring was a quick job after I was graded...I had taken apart the project but forgot I wanted to film it!

The motor was the one included in the K'Nex kit and is pretty much served it's purpose and it was for one project only...calling it junk however is a little harsh...the program worked and it executed perfectly-so, I am happy!

In th world, I would of course have something more stable than a toy ferris wheel...

Concerning the comments on the film, I was talking to someone that did not turn in his assignment and waited to the last minute...there was no doubt but an observation that one of the magnets was not activating the reed sensor on a dry run....

Anyway, before heading out, thank you for any input that you put in and have been quiet for suggestions as I was trying to figure out on my own and had finals to study for

 

[OkiePC]

See, if you had said that earlier something like 'hey here it is this project can only consume 15% of my college attention, I just gotta get by thanks'. Or 'I have $19 to eat this week and one small pile of junk with which to get this grade', but most importantly, 'This Kinex ferris wheel I gutted is ... tall and has ... seats ...'.

It's Kewl, OldsSkewl. I should also applaud your open-ness and willingness to expose yourself to the slanted criticisms of a bunch of old phaarts.

Paul

 

[Lancie1]

..the program worked and it executed perfectly-so, I am happy.

Great, but it is never too late for some "lessons learned".

I learned something watching your video. For 2 minutes, the focus was on a PLC input, the reed sensor switch at the bottom of the wheel. Why? I kept thinking, "when is he going to show the devices doing the work, the motor, the gearing, the PLC, and the program?" Instead we see the picture of the seat switch while the wheel goes round and round. Obviously this little switch is supposed to be Very Important. Why?

I think the answer is related to my previous quesion asking why students focus on the Inputs:
http://www.plctalk.net/qanda/showthread.php?t=78143

In this case the reed switch was supposed to signal to the PLC that a seat was in the Unload/Load position, so that it could be stopped at exactly that point. Many of us tried to figure out ways to make that happen. Unfortunately you concentrated on ways to have The Switch do the work of making the wheel stop. In reality, the only device controlled by the PLC that could stop the wheel was the motor. Most any good programmer could have made the wheel run through its cycle (using timers) without ever looking at that Very Important Do-Nothing Switch. So in the final program, does the switch actually stop the wheel? I bet on "NO!". Instead, the motor is cogged to a stop by a reversed voltage and a timer, when the switch happens to be closed. It appears to work, the sun is shining, the bees are buzzing, and some wrong ideas were learned.

Finally after 2 minutes, I saw the entire wheel and realized that a simple spring brake rubbing against the seat top horizontal hanger would have stopped the wheel in the forward (loading) direction, at any seat with no motor reversing needed. With a little testing, the spring could be made to compress as the wheel braked to a stop, then decompress as the wheel reversed slightly until the seat settled exactly above a loading position. As any PLC program, it needs careful complete control of the motor. The genius should be in the program, not in the switch inputs.

 

[Lancie1]

Ideally, the reed switch (probably a photoswitch would have been more flexible) should have been on a movable support mounting, so that it could be moved or position-adjusted to offset the coasting of the wheel. Then the switch could have triggered the motor to Stop, and the wheel would continue until it coasted to a stop exactly above the loading position (due to a spring brake).