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Author Topic: move rod 30 cm back and forward in a straight line  (Read 2893 times)
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Hi, I want to use arduino to move a thin, lightweight and rigid plastic rod approximately 30 cm back and forward in a straight line. What is the easiest and most inexpensive arduino solution for that?

I can't just attach the rod to a servo because that would give a circular motion. What other actuators or machinery could I use?


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I don't think you connected the grounds, Dave.
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What is the easiest and most inexpensive arduino solution for that?
Tie the rod to a hamster, and use the Arduino to stick a pin attached to a servo into the hamster's derriere.

Seriously, what sort of displacement, and how fast and accurate does it need to be?
« Last Edit: July 24, 2011, 07:29:56 am by AWOL » Logged

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Hi there. The rod needs to move 30 centimers "out" and then 30 cm back "in" again. I must control and change the movement from arduino. It should for example be possible to move the rod 10 cm, stop, move 5 cm more, move 15 cm back, then move all the way out. Speed is not very important. It would be a plus if it could move "out" from 0 to 30 centimeters in about 3 seconds.
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KE7GKP: I need to move a rod 30 centimeters in a straight line. I'm not sure how the piston will achieve that. The piston arm is not moving in a straight line. I guess I could replace the yellow block in the illustration with the rod. But then I'm still not sure how to get it to move in a straight line. Did you have any idea for that in mind?
edit: the rod should extend 30 cm "into the air". The 0-30cm part of the rod that is extended at some time can't be attached or rest in any surface.

I can't think of any more details that are really relevant for the question.

Are there no actuators that work extend itself similar to how you manually extend the handle of a compact umbrella?
« Last Edit: July 24, 2011, 09:54:31 am by roiny » Logged

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But then I'm still not sure how to get it to move in a straight line
It looks to me like the piston is moving in a straight line.
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Another method is to use a stepper motor attached to a thread rod, and then have a threaded follower travel up and down the rod as the motor rotates in either direction. You can use end of travel sensors to detect the start and ending points of travel you want, using either optical or magnetic sensors. This can be scaled small or large as stepper motors come in all sizes.

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AWOL: Sorry, I meant the connecting rod for the piston. I don't know this terminology well.

retrolefty: that sounds complex and expensive. Is there any kit for that that I can just plug the rod into and then control from arduino? Can you give an example of some arduino project that uses such a solution. I get zero hits for this search: http://www.google.com/search?q=arduino+"threaded+follower"

« Last Edit: July 24, 2011, 10:06:45 am by roiny » Logged

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retrolefty: that sounds complex and expensive. Is there any kit for that that I can just plug the rod into and then control from arduino?

I'm sure that somewhere out in the industrial world there is a linear actuator that you could use, but if would probable cost hundreds of dollars if not more. Part of being a hobbyist is figuring out how you can build your own components out of simple and inexpensive parts, rather then hoping there is a plug and play solution ready for you at a price that your willing to pay. 300mm travel is not a simple task, and you have not given use torque requirements, travel speed requirements, size restrictions, power requirement limits, etc.

Here is one linear actuator that has 12" of travel, it uses a geared motor and a threaded rod method:

http://www.pololu.com/catalog/product/2312

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KE7GKP: Please believe me when I say that I can't think of any more details that are important and would not only distract and that I'd rather not go into. If that is frustrating then think of this made up scenario and you'll be in the right ballpark for the type of movement and action I need:

MacGyver needs to from a distance extend a rod through air and very lightly press a button with it. But there is no problem if the button is pressed hard either. If he doesn't move the rod in a straight line laser sensors will sound an alarm that means trouble. (MacGyver also has no shoestring, chewing gum or paper clips at hand so there are no quick workarounds. He needs Arduino!)

My question also seems relevant in general. There might be many possible arduino projects that need to control the protrusion of a rod for a certain distance. Either there are already threads with such solutions that work well with arduino in which case I'm very thankful to get links to them as I didn't find them when searching (is there some way to limit forum searches to only keywords in thread titles?). Or there are no threads with such solutions in which case it could be of use to others to here discuss such solutions more in general.

retrolefty: thanks, I didn't know the term "linear actuator". http://en.wikipedia.org/wiki/Linear_actuator That's what I'm after. The linked one is very expensive. So let's go back to DIY alternatives. You wrote
Another method is to use a stepper motor attached to a thread rod, and then have a threaded follower travel up and down the rod as the motor rotates in either direction.
Is "threaded follower" the technical term to use when looking for components to buy? Or are there other, better terms for such a component? Stepper motors and thread rod are easy to come by. There will be no noticeable pressure on the rod in my use case so a very small rod (and similarly small size of the other components) would work fine. It can also be somewhat larger if that means the parts are easier to find or more inexpensive.
« Last Edit: July 24, 2011, 10:46:48 am by roiny » Logged

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Get a length (>= 30cm) of threaded studding and couple a motor to one end of it.
Attach your plastic rod to a nut that is incapable of rotation (constrain it in a channel, or stop the rod) and screw the studding into the nut.
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AWOL: I'm right now reading up on details in other threads for coupling of a (stepper) motor like that. I took what retrolefty wrote about a "threaded follower" to be a component for that. If you know of any particularly useful prior arduino projects that have implemented that then please post a link. Also, alternative names for such a coupling component are useful so I know what to look for/ask for when purchasing it. If such parts are easy to find in some type of discarded electronics then that would also be useful information.
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Please believe me when I say that I can't think of any more details that are important and would not only distract and that I'd rather not into

That's probably due to you not being to wrap your head around what is needed to make your project successful. You seem to be playing the game of "keep bring me ideas and I will tell you when I am happy".

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(MacGyver also has no shoestring, chewing gum or paper clips at hand so there are no quick workarounds. He needs Arduino!)

An arduino is an electronic device that really has little to do with the mechanical issues which are troubling you.
You may do well to do some research on mechanical linkages and movements. You could make a very small scissor lift, a DIY linear actuator (I've seen a small one on youtube using a servo motor), a push/pull cable like the ones in bicycle controls, telescoping rod sections, ada, yada, yada.
The best way to search this forum and the old forum is to use the Google advanced search page (below), using the site/domain option at the bottom of the page.

http://www.google.com/advanced_search?hl=en
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KE7GKP & zoomkat: thanks for the feedback again but If I can just figure out a solution that works in the MacGuyver scenario then I'll sort things out from there. So let's just assume that is exactly the use case at hand. That is a pretty straight forward use case I think. I'm under the impression that it is ok to post here even when you don't know all the proper terminology and aren't even natively english. I also thought this forum section was a fitting place for general and initial project questions that relate to both arduino and hardware. The mechanical issues I'm asking about are arduino related since I'm in the end looking for a solution that is arduino controlled. So even if there are 15 different mechanical ways to do this I was hoping there'd be some prior cases of DIY solutions for this with a working arduino system and that was suitable for a beginner and not very expensive.


You could make a very small scissor lift, a DIY linear actuator (I've seen a small one on youtube using a servo motor), a push/pull cable like the ones in bicycle controls, telescoping rod sections, ada, yada, yada.
I will do more searches using those terms. But I keep getting loads of hits even when I try to narrow the search. I guess there just are so many posts with "motor" and "linear" in them. That's why I'm hoping for anyone familiar with specific working solutions made to work specifically with Arduino could post a link to a thread with such a project. I'm also doing searches for a component that I (somehow) secure to a stepper motor cog and that then moves a threaded metal rod. Information on product names for such a component and on how to secure it to a stepper motor are of help here. I found this http://www.instructables.com/id/Quick-and-easy-electric-cylinder-prototype-.../  but using superglue can't be very durable.
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Look up DIY CNC machines. In particular the reprap 3D printer project has all sorts motors coupled to threaded rods and nuts.
You seem to want the world to conform to your way of describing things. It is better if you try an learn what everyone else calls things.
You want a liner actuator, have you looked for this? After you see the prices you will consider threaded rods and nuts.
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Grumpy_Mike: I apologize if I used the term incorrectly. "linear actuator" was mentioned earlier and I thought it could be used as a generic term for an actuator with the functionality of protruding something linearly. I only want that functionality. I'm very open to a solution with threaded rods and nuts. But I'm looking for details on just how to get that to work out, specifically the part that goes between the threaded rod and the motor.
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