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mag
09-29-2008, 09:09 AM
Hi, i'm new at this I just ordered the basic stamp kit and this is what i'm attempting to accomplish.

1.- I need to monitor line speed on an assembly line.

2.- I need a photosensor to "see" the product

3.- use the line speed to find out how fast the servo needs to run
···· (how do I make the servo turn faster?)

4.- When product is detected·Servo will do 1/3 turn than stop and wait for the next product detected
···· (I don't know how to do this.· Do I need a standard servo? or·the contious type?)

5.- that's it! simple........ right???

Basic idea is the servo needs to turn faster as the line speed on the assembly line increases.
And it will always do 1/3 turn.·

Mike Green
09-29-2008, 09:27 AM
I don't think a servo will work for you. You probably need to use a stepper motor.

A conventional servo will move through roughly a 180 to 270 degree range of motion only. There are mechanical stops at the end of this range. You can somewhat control the servo's speed by changing its position slightly as much as 50 times a second.

A continuous motion servo allows control of the servo's speed and direction, but there's no control of servo position. You can't reliably and accurately turn it 1/3 of a turn for example.

A stepper motor allows you to accurately control the position and speed of the motor, but needs a controller. You can either buy a controller (like from Parallax) or you can use the Stamp as a controller by adding switching transistors to turn on and off the power to the motor windings. There are Nuts and Volts Columns on this subject that you can download from Parallax. Go to the main web page, select the Resources tab, then use the Nuts and Volts Columns link to see the index.

mag
09-29-2008, 09:39 AM
Thanks for replying Mike.

Ok, here's what i know so far.

1.- scratch the servo idea and move to stepper motor.

2.- Do my homework and read the Nuts and Volts columns.

Question:

I would need a control for the motor plus the Stamp to control the rpm and photosensor inputs am I right?

Mike Green
09-29-2008, 10:09 AM
Download the StampWorks Manual and source code files (www.parallax.com/Store/Microcontrollers/BASICStampModules/tabid/134/txtSearch/stampworks/List/1/ProductID/144/Default.aspx?SortField=ProductName%2cProductName (http://www.parallax.com/Store/Microcontrollers/BASICStampModules/tabid/134/txtSearch/stampworks/List/1/ProductID/144/Default.aspx?SortField=ProductName%2cProductName)) and look at Experiment #27 starting at page 150. This discusses controlling a stepper motor using a Stamp and a stepper motor driver (for handling the voltage and current required).

Read the "What's a Microcontroller?" tutorial to learn how to program a Stamp. Chapter #7 goes into detail on the use of photosensors.

mag
09-30-2008, 07:17 AM
Ok, I went to the Nuts and Volts section and found quite a bit of information
nothing really specific to what I'm trying to accomplish.

Thanks for the reference to the stamp works manual.
I'm reading it right now.

One question though, my application might need a
significantly larger size stepper motor than what is
described on the manual, does this
deviate me from what the manual says? or will it
be the same exactly as far as what I need to make it work?

Another question about stepper motors.
Are there limiting factors to how fast·it
can spin? like mechanically?

I'm just wondering because I sat down and did the math
on how fast I might want this motor to run and
given I need it to move 1/3 turn, per event
this means it will need to do 1/3 turn 10 times per second.·(12,000rpm)

(that would be continuous speed but there's a gap between each product
which triggers the movement, so maybe 12,000rpm is a bit much.)

that's the fastest I might need it to go.
I of course will start slower much slower maybe 1/3 turn 3 times per second.·(3600 rpm)
and increase the speed from that point.

I hope I made sense..

Mike Green
09-30-2008, 07:24 AM
The faster and the bigger the motor needs to be (any motor), the more energy it takes. You'll need to use a higher voltage and supply more current. From the microcontroller's standpoint, you will need a bigger controller and a bigger motor power supply. I can't give you specific advice since I have limited personal experience with stepper motors. Perhaps someone else will chime in with suggestions.

Franklin
09-30-2008, 09:04 AM
I think you math is off 1/3 *3 * 60 = 60rpm and 1/3 * 10 * 60 = 200rpm

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- Stephen

mag
10-01-2008, 09:24 PM
Thought I was gonna get some advice on stepper motors.

but no..·Instead I got·a math lesson.

Thanks, you are right!!

That leaves me a whole lot of rpm to play with! meaning perhaps a more
affordable stepper motor.

Anyone with stepper motor specs? or suppliers? I need a larger stepper motor for my app.

mag
10-01-2008, 09:27 PM
Mike Green said...
... From the microcontroller's standpoint, you will need a bigger controller and a bigger motor power supply...
Ok, does this mean the BASIC Stamp won't cut it?
or maybe just the controller I connect to the BASIC Stamp.?

·

Mike Green
10-01-2008, 09:40 PM
No microcontroller can directly handle the voltage and current required for a motor. You always need some kind of external switches. This can be something as simple as one or more power transistors. Bigger motors require bigger power transistors and sometimes other circuitry around them to protect against the power surges involved. The Stamp should do just fine for what you want as shown in the StampWorks manual. You're not doing anything really complex. Sometimes, if the Stamp has to do other things as well, it's better to use an external motor controller that can handle some of the work itself like maintaining the motor's speed without any attention or changing the speed and/or direction over a period of time.

Bruce Bates
10-01-2008, 09:46 PM
mag -

Mike was speaking of the equipment that is external to the Stamp. If you don't mind me saying so, before I went shopping (expensive!) stepper motors and stepper motor drivers, I'd spend a bit of time educating myself about stepper motors and their characteristics. At least learn the appropriate terminology so you can intelligently select an appropriate stepper motor.

The steppers you will find at the link below are NOT CHEAP, but they probably have more kinds of high quality steppers than most anywhere else I've shopped. In addition, you will get top notch assistance if you need it. Sometimes it's not just the product you're buying, but the support behind it as well. If you need some links to read up on steppers, just ask.

Here is the link: http://www.danahermotion.com/website/usa/eng/products/motors/stepper_motors.php

Danahermotion bought out Pacific Scientific, which is the company with whom I dealt.

Often times these very same stepper motors can be found new, and unused from surplus houses, so let me know which stepper you're planning to purchase and perhaps I can save you some money.

Regards,

Bruce Bates

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When all else fails, try inserting a new battery.

Post Edited (Bruce Bates) : 10/1/2008 3:00:09 PM GMT

mag
10-02-2008, 01:25 AM
Bruce Bates said...
mag -


... The steppers you will find at the link below are NOT CHEAP, but they probably have more kinds of high quality steppers than most anywhere else I've shopped. In addition, you will get top notch assistance if you need it. Sometimes it's not just the product you're buying, but the support behind it as well. If you need some links to read up on steppers, just ask.

Here is the link: http://www.danahermotion.com/website/usa/eng/products/motors/stepper_motors.php

...


Thanks for the heads up, infact price wouldn't be so much a concern as much as reliability is.· I'm doing this for an industrial application so what I'm really looking for
is a quality stepper motor and driver, I think the Basic Stamp will do me good since it is really easy to program (though i've seen).

Of course saving a few bucks on the purchase wouln't hurt either. =)

I'm asking questions and like you said trying to get all the facts to be able to make an intelligent decision.

Also the space available on the machine this application is going is limited, so need to look up motor dimensions as well.

If you have some more links please pass them on =)

Thank you all for your input.

Bruce Bates
10-02-2008, 02:46 AM
mag -

Here is a tutorial on simple stepper motors:
http://www.cs.uiowa.edu/~jones/step/

When you're through with that, let me know where you want to go.

Regards,

Bruce Bates

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When all else fails, try inserting a new battery.

mag
10-02-2008, 11:08 AM
Weeee! that's a·rock'm sock'm kinda·tutorial on stepper motors!!!!!

Anyway I skimmed thru it, and what I learned so far from it is
that there are several ways to build a stepper and the way
it's controlled varies depending on it's build type.

One question, I also noticed there are steppers with
finer steps than others, which I think makes them
more expensive.

I need to rotate what ever stepper i purchase·120 deg. at a time
so maybe·coarse stepping is what i need.

I'm not sure though if the finer the step the higher the
price on a motor, but i'm assuming so.
Correct me if I'm wrong. =)

And well All I need to do is build a system that will read a line speed.
use that as a multiplier to turn the stepper 120 deg. thus controlling
how fast it turns depending on line speed.· All this triggered using
a photosensor.

(I don't do much electronic/electric setups, i'm more of a nuts and bolts kinda guy)

Most of the terminology in the tutorial is well beyond the scope
of what i'm willing to dig into the subject.
it gets down to every minute detail possible about steppers, so yes
I missed quite a lot of info, but sincerely i doubt i'll be worrying much
about steppers after this project is completed. (or so I hope.)

Bruce Bates
10-02-2008, 11:50 AM
mag -

I never really checked the price of steppers based on the fineness of their step, so I really can't answer that question. The following folds into this answer as well as another in your post.

The degree angle (amount of movement) per pulse does vary between stepppers. Some degree angles are considered "standard" and others not so. Generally standard degree angles cost less than those that are not.

As a bit of an aside, I thought I was going to go broke when I had to source a fairly large, precision stepper with a ONE DEGREE step angle. That is VERY non-standard. However, I found out that one degree angle steppers are NORMAL in high speed, 9-track tape drive as used on mainframe computers. I ended up paying less than $50.00 for a surplus, precision, high speed, one degree stepper that I thought might cost me over $500.00. It pays to look around, and not buy the first stepper you find for a particular application.

I'm not sure what you mean by a "multiplier", but you may wish to consider the following. Steppers can be obtained with gearheads. Thus, you can take a given stepper and increase either the torque or the speed (not both).

Here are some other things to consider. Heat is always a factor when sizing and sourcing steppers. So too mechanical attachment, as a loosely attached stepper operated at a high rate of speed at many steps per second, can tear itself up in no time at all. Think of the action of a rotary jackhammer on a small scale.

Another confusing part about steppers is the rated voltage vs. the operational voltage. It would not be uncommon at all for a stepper with a rated voltage of 2.4 volts to be run at 24 volts! Often the stepper controller will take care of this, but it's good to know up front.

If you need more information about anything specific, just ask. An excellent source of information is the many CNC web sites. Many of those guys are stepper geniuses.

Regards,

Bruce Bates

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
When all else fails, try inserting a new battery.

Post Edited (Bruce Bates) : 10/2/2008 5:06:26 AM GMT

Bruce Bates
10-02-2008, 11:50 AM
mag -

I never really checked the price of steppers based on the fineness of their step, so I really can't answer that question. The following folds into this answer as well as another in your post.

The degree angle (amount of movement) per pulse does vary between stepppers. Some degree angles are considered "standard" and others not so. Generally standard degree angles cost less than those that are not.

As a bit of an aside, I thought I was going to go broke when I had to source a fairly large, precision stepper with a ONE DEGREE step angle. That is VERY non-standard. However, I found out that one degree angle steppers are NORMAL in high speed, 9-track tape drive as used on mainframe computers. I ended up paying less than $50.00 for a surplus, precision, high speed, one degree stepper that I thought might cost me over $500.00. It pays to look around, and not by the first stepper you find for a particular application.

I'm not sure what you mean by a "multiplier", but you may wish to consider the following. Steppers can be obtained with gearheads. Thus, you can take a given stepper and increase either the torque or the speed (not both).

Here are some other things to consider. Heat is always a factor when sizing and sourcing steppers. So too mechanical attachment, as a loosely attached stepper operated at a high rate of speed at many steps per second, can tear itself up in no time at all. Think of the action of a rotary jackhammer on a small scale.

Another confusing part about steppers is the rated voltage vs. the operational voltage. It would not be uncommon at all for a stepper with a rated voltage of 2.4 volts to be run at 24 volts! Often the stepper controller will take care of this, but it's good to know up front.

If you need more information about anything specific, just ask. An excellent source of information is the many CNC web sites. Many of those guys are stepper geniuses.

Regards,

Bruce Bates

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
When all else fails, try inserting a new battery.

Geekgirl
10-02-2008, 06:49 PM
·

· Mag,

·Since steppers can start and stop quite quickly, would it be perhaps easier to set the speed·just above·whatever the max possible line speed would need, and then use the photo sensing system to be simply an "event" trigger where the product reaches a certain point, triggers the sensor,·the servo spins to the desired location and then waits for the next trigger?



· Darlene

mag
10-03-2008, 12:07 AM
To relate better what i'm trying to accomplish here's a link to a video.
at minute 1:20 illustrates exactly what i'm trying to do.

Fact is different products are run at different line speeds
that's why I think I need to monitor line speed and than use that
to figure out how fast the stepper needs to turn every time
the event is triggered.

(fast forward to minute 1:20)
Here's the link: http://www.youtube.com/watch?v=Vpas57jbh5U

Actually machine showed on video is been ran quite slow for the
purpose of showing the process.

Actually here's another link to a video wich represents the process
truer to life. =)

(Again fast forward to minute 1:20)
http://www.youtube.com/watch?v=EY4-FHfMrjU

The line speed on a given product starts out always slow for set up purposes,
than it is gradually incremented until the max running speed for that
particular product is reached

Yes, i need to actuate a 3 spade mechanical attachment most likely made
out of aluminun, to fold a back flap on a carton.

Post Edited (mag) : 10/2/2008 5:13:16 PM GMT