Need help with reed sensor in ferris wheel

[oldskewl]

After deciding to put a reed switch on my model ferris wheel, I am having issues with the darn thing.This is what I have so far:

[I:2/4](XIC)------------JMP

[I:2/3](XIC)-----[I:2/4](XIO)-------TON1
| |
|--------[T4:3/DN]((XIC)----|

[T4:1/EN](XIC)---------------------[OTL](O:3/4)

[T4:1/DN](XIC)---------------------[OTU](O:3/4)

[T4:1/DN](XIC)----[I:2/4](XIO)-----TON2

[T4:2/EN](XIC)---------------------[OTL](O:3/5)

[T4:2/DN](XIC)--------------------[OTU](O:3/5)

LBL-----[I:2/4](XIC]---------------------------TON3
| |
---[T4:3/EN](XIC)-[T4:3/DN](XIO)--

[T4:3/EN](XIc))-------------------------[OTU](O:3/4)

[T4:3/DN](XIC)--------------------------[OTU](O:3/4)

Ok...I:2/4 is the reed sensor and O:3/4 is forward and O:3/5 is backward...
the problem is how can I stop the reed switch activating whenever the magnet comes close to the swithc when it is going forward and backward without wanting to load/unload (that is what the reed switch is for) hypothetical people. Any assistance will make me very happy. Thanks in advance!

 

[oldskewl]

anyone?

 

[randomFire]

What determines when you don't want to load/unload?

 

[oldskewl]

What determines when you don't want to load/unload?

That is what I am asking for help with. I have never worked with reed switches and need some proverbial nudging.

 

[oldskewl]

What determines when you don't want to load/unload?

Okay, here is what I am wanting to do (panic mode is starting to set in):
Load/Unload at the beginning (I assume that involves the reed sensor)
Go forward twice around and go backward twice around
Load/Unload

I also am going to add a photocell to simulate someone waiting in line and after the cycle is complete...load/unload

I REALLY NEED HELP WITH THIS!

 

[Lancie1]

You might want to look at the programs in this thread from member "bobc1957" for a model of the Hershey Park, in Hershey PA, including the loading, running, and unloading of a double Ferris Wheel. This program was based strictly on time cycles. A sensor certainly would make it better.

http://www.plctalk.net/qanda/showthread.php?t=38078&highlight=double+ferris+wheel&page=2

I suggest that you list all the controls that you have available, all the input-type sensors, switches, photoeyes, and then all the output-type items that need cotrolling, such as your Ferris wheel motor forward, motor reverse, and any other devices involved. Then someone can help you to find the correct logic.

 

[Lancie1]

Here is a print-out of the RSLogix500 program on a SLC-5/02 with 3 I/O modules. I see many ways to improve and simplify this logic. Suggestions?

Could I:2/3 be START/STOP Maintained-contact Switch?

Is this the correct cycle?

(1) When Reverse motor direction goes off or is off at start-up, look for closed reed switch and brake wheel at that point.
(2) Load people. (This is not implemented now but the wheel could move incrementally for 3 seconds and stop, then repeat for the number of seats until all are unloaded and loaded).
(3) Run forward for 30 seconds (model time!).
(4) Kill forward motor and wait for wheel to brake, or coast to a Stop.
(5) Run Reverse for 30 seconds.
(5) Repeat cycle (go to Step 1).

 

[oldskewl]

Here is a print-out of the RSLogix500 program on a SLC-5/02 with 3 I/O modules. I see many ways to improve and simplify this logic. Suggestions?

Could I:2/3 be START/STOP Maintained-contact Switch?

Is this the correct cycle?

(1) When Reverse motor direction goes off or is off at start-up, look for closed reed switch and brake wheel at that point.
(2) Load people. (This is not implemented now but the wheel could move incrementally for 3 seconds and stop, then repeat for the number of seats until all are unloaded and loaded).
(3) Run forward for 30 seconds (model time!).
(4) Kill forward motor and wait for wheel to brake, or coast to a Stop.
(5) Run Reverse for 30 seconds.
(5) Repeat cycle (go to Step 1).

1. Load/Unload first
2. Forward for 30 seconds (yes I:2/3 is continuous)
3. Reverse for 30 seconds
4. have photocell that represents someone waiting in line- if tripped will wait until forward/reverse is done and will go through seats to find spot for customer
5. repeat

Each seat will have a magnet on it (4 seats) and going over reed switch will be used to lock the seat for 5 seconds for the individuals to unload/load and move on...how can I implement the above to make this thing work?

Thanks for your help.

 

[daba]

I don't think I've ever seen a Ferris Wheel go backwards ?? "But I ain't seen nothin' yet. B-B-B-Baby I ain't....."

Anyway, the point of the post is to warn against using JMP/LBL in your program. This "problem" can be solved with plain, straightforward, easy to understand, vanilla, logic.

One of the drawbacks of JMP/LBL is that if you are viewing the code (as in, debugging), and you can't see the JMP or LBL on the screen, how do you know whether the logic you are looking at is being solved by the processor?

Another drawback is that any "outputs" (and I'm not just talking about physical outputs, but internal bits as well), become "frozen" when you jump that section - this can be a disadvantage.

Another drawback of JMP/LBL is that it makes your code "position dependant" - meaning that any future modifications to the program are harder, because you have to go search out JMPs and LBLs to determine where to put a new rung of ladder, so that it is, or not, affected by the JMP.

Thinking about the Forward/Reverse, if it were my model, I would have two-speed instead. Fast for the enjoyment of the riders on the "paid for" cycle, and Slow, for the loading/unloading where the wheel has to increment round and stop for a while at each seat. During the slow cycle, I would use a counter, and stop the wheel a certain number of times (= the number of seats), to allow unloading/loading.

 

[Lancie1]

Each seat will have a magnet on it (4 seats) and going over reed switch will be used to lock the seat for 5 seconds for the individuals to unload/load and move on...how can I implement the above to make this thing work?

No problem, we worked it out for BobB for the entire Hershey Park model, so this should be a picnic! What we did there was use an overall Cycle Timer for each ride, then used comparison instructions to do different tasks within the cycle time, sometimes needing additional timers triggered at a certain cycle time. In your case, the total cycle time will be variable depending on how many people are waiting, so probably just a straight series of events triggered by timers will work best. I will start work on it. When do you need it?

 

[oldskewl]

No problem, we worked it out for BobB for the entire Hershey Park model, so this should be a picnic! What we did there was use an overall Cycle Timer for each ride, then used comparison instructions to do different tasks within the cycle time, sometimes needing additional timers triggered at a certain cycle time. In your case, the total cycle time will be variable depending on how many people are waiting, so probably just a straight series of events triggered by timers will work best. I will start work on it. When do you need it?

Before saturday if possible...is that possible?

 

[Lancie1]

I have made a rough outline with the outputs, timers, and Step latches. Take a look and see if you think this is the right approach. Also add anything that I have missed.

 

[Lancie1]

Here is a correction, and a few more additions. The Run Reverse Timer on Rungs 007 and 008 was a copy of the Run Forward timer that I failed to change to T4:4. Keep working, you will get there. All you need to do now is fill in the remaining inputs on the left side of the rungs. I am going to convert the program to a LogixPro simulator file and run it to find any remaining errors, and to help finish up the bells and whistles.

Do you know how long of an ON pulse it takes your RUN FORWARD motor to advance the wheel to the next seat position?

If I knew that, I could set Timer T4:2 to the correct time. I think this timer probably needs to be changed from a 1-second time to a 0.01 time base to allow more accurate control of the motor to stop the seats at the correct position. For example, instead of setting T4:2 to 1 second or 2 seconds, with a 0.01 time base, T4:2 could be set to 1.5 seconds, or 1.4 or whatever is needed to make the seat stop at one of your reed magnets.

 

[shooter]

slow speed to sensor.
wait 10 seconds
slow speed until sensor has a positive trigger (it was negative)
wait again 10 seconds.
do this four times.
now lets party run for 30 seconds.
if timer passed then go to start.

 

[shooter]

allright lancie can i have a round free please