Micrologix 1000 DC Motor control.

[TheStarr]

Ok, I feel much better now knowing that no one's life is at risk.

So on to the brakes. I wouldn't even try to create my own brake system. It would be much easier to buy a motor with an integrated brake.

But for what you are doing, a stepper is the correct thing to use.

We mostly use the 3540 MO controller ($275 each) for industrial conveyor applications. You would need one for each motor, and the stepper motors of course.

But if it were me trying to do this project, I would use something like this:
http://cgi.ebay.com/3-Axis-Stepper-...in_0?hash=item19b3691590&_trksid=p3286.c0.m14

A 3 axis stepper setup. It is designed to run on PC Software, but could easily be modified for PLC control.

Do that and I assure you will learn some very valuable knowledge.
http://www.omega.com/ppt/pptsc.asp?ref=3540M&Nav=autj01

 

[bigoldblack]

Ok, I feel much better now knowing that no one's life is at risk.

So on to the brakes. I wouldn't even try to create my own brake system. It would be much easier to buy a motor with an integrated brake.

But for what you are doing, a stepper is the correct thing to use.

We mostly use the 3540 MO controller ($275 each) for industrial conveyor applications. You would need one for each motor, and the stepper motors of course.

But if it were me trying to do this project, I would use something like this:
http://cgi.ebay.com/3-Axis-Stepper-...in_0?hash=item19b3691590&_trksid=p3286.c0.m14

A 3 axis stepper setup. It is designed to run on PC Software, but could easily be modified for PLC control.

Do that and I assure you will learn some very valuable knowledge.
http://www.omega.com/ppt/pptsc.asp?ref=3540M&Nav=autj01

Getting the set of stepper motor seems very nice but since I'll already have my motors coming, I will test them out first before thinking of going this route.

If I were to not use the PLC at all and use the software provided, would it be possible to do something like this:

I have 9 pushbuttons, one for each parking spot, If I push one button, can it automatically be programmed to move to the certain location. I know this is possible using ladder logic as I've done something similar.

If it is possible doing that, I'll really consider it. Just by looking at the controller, it doesn't seem to have any extra wiring for me to put pushbuttons in.

Maybe I need to get a closer look at the circuit. But this is certainly an option I could be thinking about. If I cannot use buttons then I'll just have to manually do this on the computer which would not look as nice visually.

 

[bernie_carlton]

Somehow, with only DC motors, you have to ahve some input verification that each movable section is at the desired destination. With stepper motors at least you have an implied feedback (X number of pulses have been issued). Otherwise you'll need something to verify that the lift (for example) is at the desired height. Unfortunately, except for safety equipment, the items necessary in the real world are also needed in a model. The DC drives I suggested (DART) will only provide power. You'll have to provide the intelligence via the PLC or whatever.

 

[Norml]

I think you could easily integrate the 1100 into the system. The Dart controllers (and others) have analog inputs that you could drive with the 1100's analog out (0 - 10V for example). If you had a limit switch before each stop position (PLC inputs), you could decelerate the motor then send a 0 volt signal to the drive to stop it. You should be able to end up pretty close to where you want to be.

As previously suggested, relays on the PLC outputs can be used to both select which motor to use and swap the DC leads to reverse direction.

Maybe holding position could be accomplished some other way such as a solenoid operated clamp - or something. Be sure to check your I/O count. Getting really fancy might require an expansion module for the 1100. Sounds like a fun project.

Oops - never mind about the analog stuff. I had the ML1100 in my head instead of the 1000.

 

[TheStarr]

Nine seperate push buttons seems like alot. Maybe you need to think on a bigger scale.

If you were the designer of a commercial car park (like the one at the Volkswagon plant in Germany) that had 200 stalls, would you have 200 buttons? Probably not.

You would need to program a GUI (Graphical User Interface) to make input to the system.

If you were to get the stepper setup, you could use HTML to inteface with software through BASIC.

From a PLC stand point, you would use a PanelView HMI (Human Machine Interface) to control the system.

If you are going to use the DC motors, then you will need a lot of I/O (Input/Output) for control. More then your current PLC has available.

At this point, it may be easier to use relay logic and micro-switches. You would have three buttons for the three vertical columns and three buttons for the three horizontal levels.

Your logic would be a lot of "If button a and button d are pressed then run motors x and y until switch a1 and d1 are made. When switch a1 and d1 are made then drive motor Z...... blah, blah, blah"

Lots or 1950s technology. Can it work, yes. Will you learn something, yes. Will that knowledge get you a job, probably not.

So really what you need to develop is a "Specification" (use the search function) to determine your goals.

Then you can decide whether your budget is large enough to accomplish your goals.

I know it seems like a pain, but getting these details worked out before you drill the first hole will save you time and money and will result in a better final product.

 

[bigoldblack]

I think you could easily integrate the 1100 into the system. The Dart controllers (and others) have analog inputs that you could drive with the 1100's analog out (0 - 10V for example). If you had a limit switch before each stop position (PLC inputs), you could decelerate the motor then send a 0 volt signal to the drive to stop it. You should be able to end up pretty close to where you want to be.

As previously suggested, relays on the PLC outputs can be used to both select which motor to use and swap the DC leads to reverse direction.

Maybe holding position could be accomplished some other way such as a solenoid operated clamp - or something. Be sure to check your I/O count. Getting really fancy might require an expansion module for the 1100. Sounds like a fun project.

Oops - never mind about the analog stuff. I had the ML1100 in my head instead of the 1000.

I can see how using the relays would work for controlling it all but I'm going to attempt to try and move more than 1 axis at once if all the ladder logic goes well. This project would be very fun if it all works out but if it doesn't, it'll be a disappointment and a waste of money. But I am determined to finish it since it's very interesting and I'm learning a lot.

Nine seperate push buttons seems like alot. Maybe you need to think on a bigger scale.

If you were the designer of a commercial car park (like the one at the Volkswagon plant in Germany) that had 200 stalls, would you have 200 buttons? Probably not.

You would need to program a GUI (Graphical User Interface) to make input to the system.

If you were to get the stepper setup, you could use HTML to inteface with software through BASIC.

From a PLC stand point, you would use a PanelView HMI (Human Machine Interface) to control the system.

If you are going to use the DC motors, then you will need a lot of I/O (Input/Output) for control. More then your current PLC has available.

At this point, it may be easier to use relay logic and micro-switches. You would have three buttons for the three vertical columns and three buttons for the three horizontal levels.

Your logic would be a lot of "If button a and button d are pressed then run motors x and y until switch a1 and d1 are made. When switch a1 and d1 are made then drive motor Z...... blah, blah, blah"

Lots or 1950s technology. Can it work, yes. Will you learn something, yes. Will that knowledge get you a job, probably not.

So really what you need to develop is a "Specification" (use the search function) to determine your goals.

Then you can decide whether your budget is large enough to accomplish your goals.

I know it seems like a pain, but getting these details worked out before you drill the first hole will save you time and money and will result in a better final product.

I have most it planned out for awhile and I knew I was going to run in some problems but I'm ready for them. The reason I don't have fewer buttons is I don't want to change the interface. I do have a microcontroller that I could be using for this which may make the finish product look a lot better but my programming skills would need review.

I chose to have 9 buttons is a because I wanted each position to be specifically programmed and located using SFC so it is easy to follow and adjust. I believe this could be implemented with a microcontroller and a numpad but thats going too far from what I want to do. If I were to do it using SFC with a lot of latches, I think I will have enough I/Os.

I want to know the basics first and if I were to have extra time (most likely not), I will try new and better ways to doing things.

 

[bernie_carlton]

I, for one, want to say hooray for someone who wants to try and experiment to work things out. This is much better than the "I have two day until my final and I require someone to give me a complete answer now!". You'll be assured of having many hints and suggestions as you progress through this learning experience. They won't be hints because we somehow know the real final answer and we're holding it back. It's because, as in the "real-world" everything is different, even a model, and we can only point in, we hope, a helpful direction.

 

[leitmotif]

OK How sophisticated does this have to be and what is the money budget?

so I looked things over
from your photos you are going to have 3 shafts with 3 slots to park 9 cars.

you are working with 3 axis ie left right up down and in out.
have some ideas.
1. Looked at the motor you intend to use and see it has no speed reduction. Even with a DC controller you are going to need a mechanical speed reducer to achieve the torque you are going to need. you are going to need some way of mechanically reducing shaft speed. Recommend a gearbox - check with Grainger for motors and controllers and with Burden Surplus for the motor/gearboxes.
2. I think the least of your problems are going to be the PLC.
3. Since you have 9 options on where to place car you could call each shaft A B or C and each slot 1 2 or 3. this would only take 6 switches and would result in nine options
switch A and switch 1 would tell it to go to bottom left
switch C and switch 3 would tell it to go to top right.
Start stop switches and maybe "place" or "get car" switches.

there will be a tradeoff with motors and controls.
Stepper will give you much better positioning control but at higher cost and a bit more complexity.
DC will be a bit cheaper including controllers but at loss of accurate position control. An encoder will allow for good position control but with a price tag.

I think I would stop and think more about how you are going to achieve position control ie in real world elevators "leveling".

interesting project otta be fun
Dan Bentler

 

[bigoldblack]

OK How sophisticated does this have to be and what is the money budget?

so I looked things over
from your photos you are going to have 3 shafts with 3 slots to park 9 cars.

you are working with 3 axis ie left right up down and in out.
have some ideas.
1. Looked at the motor you intend to use and see it has no speed reduction. Even with a DC controller you are going to need a mechanical speed reducer to achieve the torque you are going to need. you are going to need some way of mechanically reducing shaft speed. Recommend a gearbox - check with Grainger for motors and controllers and with Burden Surplus for the motor/gearboxes.
2. I think the least of your problems are going to be the PLC.
3. Since you have 9 options on where to place car you could call each shaft A B or C and each slot 1 2 or 3. this would only take 6 switches and would result in nine options
switch A and switch 1 would tell it to go to bottom left
switch C and switch 3 would tell it to go to top right.
Start stop switches and maybe "place" or "get car" switches.

there will be a tradeoff with motors and controls.
Stepper will give you much better positioning control but at higher cost and a bit more complexity.
DC will be a bit cheaper including controllers but at loss of accurate position control. An encoder will allow for good position control but with a price tag.

I think I would stop and think more about how you are going to achieve position control ie in real world elevators "leveling".

interesting project otta be fun
Dan Bentler

I would say I still have around 200-300 to spend. I like the idea of having the six switches but I believe I would need additional program in the beginning and end of each sequence because of the lift needing to go in and out. This would save me on 3 extra switches though.

Anyways, I received the motors over the weekend and went to an electronic store and got an adapter with an output of 24vdc 1A rating. I tested out one of the motors and went really smooth. I haven't finished building my 3-axis yet so I can't tell how accurate it is.

I'm also worried about the speed of the motor as I was operating it with the minimum voltage. I'm planning to hook some relays onto the PLC to save some outputs for forward and reverse.

What is a good relatively cheap sensor I could use to locate each position or would that not help either? and the price?
I found a lot of them but don't know which would be good for this type of application.

Thanks,

Ben

 

[leitmotif]

If you are trying to learn motor control then by all means stay with project as planned.

OTHERWISE
Another good option and maybe cheaper would be hydraulic or pneumatic. Most college workshops labs have compressed air so pneumatic would maybe be better option at
the loss or cost of poor position holding in cylinder mid stroke.
Limit switches would be less expensive than encoders on motors for postion sensing and throtttle valves would suffice for speed control.

With motor drive I would consider using encoders for both speed and position control and limit switches as final position or safety stops.
In real world I would almost always have a safety limit switch in addition to encoder position sensing.
Dan Bentler

 

[gfr]

A proper installation must have a holding mechanism for each floor to prevent the lift from dropping if the power goes down. A solenoid locking pin would be best but a fail safe(fail secure) type brake would also be a good option here.

I agree with a previous poster who mentioned that you will need mechanical speed reduction. A gear reduction would help maintain the position if you use a worm or a helical gears.

Limit switches are a good cheap way to feed back to the plc. Some limit switches have rollers on the arm that will operates smoothly over a track and when the roller rides into a depression the switch de-actuates.

You might want to hit some surplus and hobby shops for parts and ideas. Find yourself an old photocopier and disassemble it for parts. The old ones use electromagnetic clutches to stop rollers, and are a good source of switches.

If I had your budget to work with I'd be doing it with 12V automotive motors driving them with a computer power supply and the relay outputs of the ML. You'll find lots of 12V motors at an auto wrecker that have really good gear reduction. Think windshield wipers, power windows, antennas, power locks power seats.

What will your lift be made out of ? And how big are these cars ?

 

[bigoldblack]

A proper installation must have a holding mechanism for each floor to prevent the lift from dropping if the power goes down. A solenoid locking pin would be best but a fail safe(fail secure) type brake would also be a good option here.

I agree with a previous poster who mentioned that you will need mechanical speed reduction. A gear reduction would help maintain the position if you use a worm or a helical gears.

Limit switches are a good cheap way to feed back to the plc. Some limit switches have rollers on the arm that will operates smoothly over a track and when the roller rides into a depression the switch de-actuates.

You might want to hit some surplus and hobby shops for parts and ideas. Find yourself an old photocopier and disassemble it for parts. The old ones use electromagnetic clutches to stop rollers, and are a good source of switches.

If I had your budget to work with I'd be doing it with 12V automotive motors driving them with a computer power supply and the relay outputs of the ML. You'll find lots of 12V motors at an auto wrecker that have really good gear reduction. Think windshield wipers, power windows, antennas, power locks power seats.

What will your lift be made out of ? And how big are these cars ?

I think I will go with using the limit switch so I can have some feedback in my circuit. As of now, I'm going to stick with the dc motor I have now as they work fine with a 24vdc 1A adapter.

The lift is made out of wood(20inches long) and the car is 1:16 model cars. I'll post more pictures tonight to show my progress.

Regarding my circuit. I plan to wire the motors like this diagram below using a total of 5 dpdt relays. This should work but I think I would only be able to control 1 motor at a time.
It can also go forward and reverse like you have stated earlier.

http://img229.imageshack.us/img229/1086/motorcontrol.jpg

 

[gfr]

If you want complete control of all three motors independantly then use 6 relays. One for each motor ON/OFF and one for each motor reverser.
A reverser can be made easily with one DPDT relay by cross wiring the NO and NC contacts. If you need a picture I can whip one up for you.