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.
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.
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.
lax123:
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?
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
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.
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.
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.
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
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.
lax123:
but idk about that pair of bellows, how to "drive" it and about its "fixed" volume with its flexible parts.
To drive it you would just need to push or pull the two sides together, easily done with a mechanical linkage operated by a servo.
I'd expect the displacement to be consistent, if not very predictable. If consistency does prove to be a problem I expect you could improve it by enclosing the bellows. I'd have thought this was much easier to build than something capable of generating enough force to operate a syringe - I'm envisaging something that takes significant force in both directions, and needs to be positioned accurately.
Bellows might have issues such as being made of flexable materials, and finding a bellows with a small area end so a lot of force isn't required to generate pressure.
Not find; make. It just needs a couple of paddles hinged together with a plastic bag trapped between them. I see this as being literally a five minute job to get something working.
PeterH:
Not find; make. It just needs a couple of paddles hinged together with a plastic bag trapped between them. I see this as being literally a five minute job to get something working.
Kind of like a zip lock sandwich bag between two pieces of wood?
That's the sort of thing I had in mind. Large quantities of tape or elastic bands securing the bag onto a small hose, and you've got the connection to the measuring chamber. The nice thing about this approach is it's all low tech and doesn't need much construction. Not as refined as motors driving nuts spinning around threaded bars all mounted in an assembly driving a syringe and all that, but I much prefer to get something simple working and then improve on it as necessary.
