Need help with reed sensor in ferris wheel

[OkiePC]

I need to make a Youtube video, how to go from state chart to state engine in thirty minutes or less.

I sense the need to "anticipate a discrete position sensor to "cog" the driven wheel to a repeatable loading position if the sensor is mounted at the very bottom.

You can do this with a timer which is used to measure the normal duration, and offset it (subtract a few ms) to drive the output, allowing for coast and stop time so that it "lands" with the sensor "made".

Measure how long it takes between pulses and set an alarm if you're supposed to be moving and it times out....reset the timer so that is doesn't nuisance fault when starts occur, and set the anticipatory timer to stop the wheel to a value a few milliseconds before the the measured time between carriages...

But first, design your program with a paper page, with circles representing each state, then arrows with the transition definitions written along them to interconnect the states, and then I will show you how to translate that into a pure state engine in RSLogix (I have to use the free version at home.)

Paul

 

[Lancie1]

Ferris Wheel Revision 3 (change in photoswhitch function to reset to Step 1.)

 

[oldskewl]

For some reason the PLC will not run the program with B3:0/2 and B3:0/3 in rung 000...and B:3/2 will not latch for some reason...also, if the person steps away from the photocell before C5:1 is done-B3:0/1 will not activate...

question from a inexperienced PLC programmer, why is the O:3/4 in rung 4? Just curious...plus, if the bits are reset, will that also reset the CTU? For some reason, the counter will not reset when the conditions say otherwise

 

[Lancie1]

I think that the Counter Reset has got deleted. Let me check.

Yes, on Rung 0003, underneath the B3:0/1 Unlatch Output, place your cursor to the left, and right-click, select "Extend Branch Down". Now add a "RES" (Reset) instruction, with address "C5:1".

Also add the Counter Reset branch to Rung 0011.

There is another error on Rung 0007. Change the 2nd instruction T4:3/DN to T4:4/DN COAST FORWARD timer.

Here is updated R4 with the above changes.

 

[Lancie1]

You kicked around several ideas for how the photoswitch should operate. What did you finally decide to do? Without any instructions or feedback, I left it as it was in Revision 2.

 

[oldskewl]

You kicked around several ideas for how the photoswitch should operate. What did you finally decide to do? Without any instructions or feedback, I left it as it was in Revision 2.

Sorry...I went with revision 2....went and tried to workthrough the program most of today and it came to the point where I was frustrated (hence the message that I was going to change everything)...BUT with revisions of the program- I am going to run the new version that you posted this evening on monay...as I have several other things that need to get done and I am burned out a lil'...

Haven't hooked up the motors yet as I wanted to get the program pat down before hooking it all up...

Thank you for your assistance again!

 

[Lancie1]

Okay, thanks for the feedback. I think you are close now. Good luck, and hang in there.

Here is the working LogixPro version, if you want to test it without a PLC, and compare it to the RSLogix R4. I am over-the-hill and not as sharp as I once seemed to be, eyesight is poor, memory foggy, so I forget more than I ever knew. To run LogixPro, you would need the software from thelearningpit.com

 

[oldskewl]

Went with what you provided and changed it around...took out some stuff like the photocell (It was a pain in the arse anyway) and included some counters to count the reed sensor contacts...awesome! It is finished except for adding in an SQO routine for the lights and that shouldn't be that hard.

Thank you for the direction...it was extremely helpful and educational!

 

[Lancie1]

Congratulations. Would it be okay if you printed your final version to a PDF file and posted it for all to share?

 

[oldskewl]

Congratulations. Would it be okay if you printed your final version to a PDF file and posted it for all to share?

Yup, will do when I get back to school and put it on the hard drive...it is quite different in some aspects then what we worked through...it's weird, I was pulling my hair out and getting frustrated as all get out...

Then I decided...calm down and start fresh...took me like 15 minutes after I dropped the photocell (my instructor told me I already had two inputs and outputs figured out)...I walked through the program switching and unswitching the reed sensor until SHAZAM! Goollllyyyyy....by juv I had it!

Now if I can get the SQO issue figured out...

 

[Lancie1]

If you have a set sequence of lights, you could make all the outputs in the last positon of the sequencer = "0" (all outputs off). This will prevent any lights from being left on when the sequencer finishes its cycle. Otherwise, if the sequencer is routinely stopped BEFORE the last position, then you have to use Clear, Move, or Masked Move to set the outputs to 0 after you exit from sequencer control.

 

[oldskewl]

Actually, I used I:2/4 [XIO] and used a CLR O:3.0...worked like a charm. SHAZAM! XD

 

[Lancie1]

I think you are starting to learn this stuff now! Be careful, it can be addictive. I have been programming for long after there was any need for me to do it. Many people do crossword puzzles for fun, while I do PLC programs.

 

[Lancie1]

Actually, I used I:2/4 [XIO] and used a CLR O:3.0...worked like a charm. SHAZAM! XD

Oldskewl, what if you had a typical situation where you used Outputs O:3/0 to O:3/6 for your ferris wheel, but Oututs 3:7 to O:3/15 were used for other equipment, maybe the tunnel of love and the roller coaster and some other rides?

Now when you do a "CLR O:3.0", the PLC will clear all bits in output module O:3, not only stopping the ferris wheel lights, but a bunch of people get stranded on the various rides. What should you do instead (if you still have a job after the customers are evacuated through the emergency exit ladders)?

 

[oldskewl]

My capstone project...I gutted a K'Nex Ferris wheel motor and created a program using a PLC500 to load a passenger, give a five second delay, and then move on to the next chair until all 8 chairs have been loaded/unloaded. After the first stage, the Ferris Wheel will go forward for two full rotations and then do the same in reverse...and then the process restarts.

Here is the link:

http://www.youtube.com/watch?v=YrSoVhvWj5k&feature=youtu.be