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Author Topic: ideas for creating linear movement/ general suggestions for approach please  (Read 1688 times)
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Hi,

What i want to ask you, is if you have maybe a better idea on how to get what i want. Maybe a cheaper/ easier way on how to do this. As this is supposed just to be an experiment those around 40€ for that motor are a bit expensive for me:

into an airtight container i want to put in a cetain fixed volume of like 40ml to create a small overpressure of like 10-20mbars.

As delivery device i thought about an syringe like this:
http://www.ebay.de/itm/100ML-Spritze-Dosierspritze-fur-Agrar-mit-Schlauch-Neu-/170867741295?pt=Infusion_Injektion&hash=item27c882d26f

i want to push and pull that syringe controlled by arduino. I doesnt matter if its possible to put in like steps between 40ml and 0ml, only 40ml pushing down directly to 0ml all the time would be perfect. What is important is repeatabilty, so it should always be those 40ml/ 4cm pushing and pulling.

For pushing and pulling i thought about a linear stepper motor like this:
http://www.ebay.de/itm/290756617726?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

Maybe you know a different cheap way to put the rotating movement of a motor into the pushing in pulling.
This principle would be a possiblity too:

but id think getting a fitting gear and wheels and everything around i need would be even more complicated, but maybe you have an idea or know where to get the stuff i need.

kind regards

« Last Edit: September 13, 2012, 03:28:19 pm by lax123 » Logged

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I don't think you connected the grounds, Dave.
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Why not a simple lead screw arrangement?
It could be driven by a stepper or a geared DC motor.
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i forgot this:



hi, thanks for the hint. could you maybe show me a google picture of what you mean. as im not english i dont know what exactly you r refering too.
« Last Edit: September 13, 2012, 03:36:22 pm by lax123 » Logged

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into an airtight container i want to put in a cetain fixed volume of like 40ml to create a small overpressure of like 10-20mbars.

I think you'll manage to find a way to pressurise a sealed container, but doing it by a specific amount might be harder. Which parameter do you need to control - is it the volume displaced, or the final pressure?
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this is my plan:

the container is of known volume, inside the container is a random amount of water, but around like 2 litres container and 0,5 water. by pushing in a fixed known volume and knowing the temperature and the current atm pressure and measuring the increase in overpressure inside i should be able to calculate the volume/amount of water inside the container. for getting atm pressure inside the container it would be opened before this syringe procedure.

i thought about a small pump or peristaltic pump but i think that would not work

« Last Edit: September 13, 2012, 05:07:08 pm by lax123 » Logged

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btw, it doesnt have to be syringe and motor at all. if you can think of any other way to reach that, arduino controlled. any suggestions r welcome :-)
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Syringe idea

http://www.lynxmotion.com/p-825-vacuum-gripper-kit-with-wrist-rotate.aspx
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I think I see what you're getting at now. Is 10-20 millibars worth of compression going to give you enough accuracy in your volume calculation?
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 I was thinking for linear movement, I would use a threaded rod connected to a stepper motor to spin the rod. You would need a bearing surface to interface the load of the threaded rod to the syringe.

 This is way too expensive but, here is an example of a linear actuator. http://progressiveautomations.com/linear-actuators-introduction-part-a-40.html
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thx,
PeterH, i hope so. As sensor i want to use mpx7002dp, 2% accuracy with zero-auto. Pressurerange -20mbar -  +20mbars. Usually i think, "stuff" has its best accuracy at the end of its range, so thats why i wanted 20mbars.
I also have an mpx5001dp, which has its range up to 100mbars, but accuracy is around 5%, maybe that would be an option too. if i have a fitting setup id experiment to see if using weight/density/temperature->volume gives same results as calculation via pressures.

cycle, i think you linked something i already have in my first post :-)
http://www.ebay.de/itm/290756617726?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

zoomkat, thx for the idea. it looks nice but also like a lot of work and hard to do, as you need the equipment, metall, tools to create something like that.
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You could maybe press the plunger with a simple cam
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Hi,

whats a simple cam? sry im not english

pushing would not be sufficient, i need pulling too.  as the backpressure of 20mbar would not be enough to put the syring / or something else back to the starting position due to (i hope thats the right term, using google translate) static friction
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A cam - like in an internal combustion engine - the thing that lifts the valves.

« Last Edit: September 14, 2012, 05:53:18 am by AWOL » Logged

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With such small volumes and pressures, I suspect you could get away with a simple hobby servo operating a pair of bellows.
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thx,

but idk about that pair of bellows, how to "drive" it and about its "fixed" volume with its flexible parts.

so far id think zoomkats suggestion link and AWOLS leadscrew r the best suggestions i could implement.


I painted what i think would work, is that what awol was talking about with his leadscrew?

I have problems finding those parts on ebay, what i call threads is that a leadscrew?
What i call screw, how would you call that? It needs to be bigger then a regular screw as i have to attach somehow that syringe.


* Unbenannt.png (7.29 KB, 578x291 - viewed 40 times.)
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