Automated fluid dropper?

Hi,

I want to release droplets of water one-by-one on command, and have been doing some research on how to do that, but I'm wondering if anyone has some other ideas or has heard of a ready-made solution.

So far I have come across:

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-peristaltic pumps with really low flow rates, like the one here

http://aptinstruments.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=AI&Product_Code=SP100VO&Category_Code=

It goes down to 0.09 ml/minute, which should be small enough. I can selectively turn the pump on and off, feeding water to a small tube or dropper end, producing the water drops. These are pretty expensive, the cheapest one I've seen is around $60.

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-DIY systems like the one pictured here with a solenoid opening and closing a safety pin on a tube.

http://www.maggiecarsonromano.com/index.php?/projects/what-made-the-wound-wound-the-thread/

Maybe I could tune the distance of the solenoid so it just opens the pin a tiny amount, and a drop or so is allowed through.

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-or I could use a more typical water pump, attach it to something with a really small aperture. I could turn the pump on and off. I have a hard time picturing drop-by-drop control with this, I might be able to release very small amounts, and maybe some 2nd reservoir between the motor and dropper could be designed to aid this.

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Is there a ready-made solution to what I'm trying to do? If I just get a regular water pump what should I look for? Ideally I'd like to get a pump that's as quiet as possible, too.

Thanks bros. Josh

How fast do you want the droplets to drop ie how many per minute and what degree of precision do you want on ensuring 100% drop count. Bear in mind that drop size and speed will be influenced by water temperature since it is surface tension that creates drops.

One idea you could use is to have a wick dippled into your supply and this will create a constant stream of droplets (determined by the wick permeability) then under the wick you have a shutter/diverter mechanism controlled by a servo motor. Drops demanded, servo rotates to show aperture, no drops demanded, servo rotates to block aperture and reroute droplets to a secondary reservoir.

Main problem with that would be synchronising drops to shutter. You'll loose some and cut some. However you could create a drop sensor such that the shutter could be synchronised to drops about to fall.

And as in all previous requestor requests, please tell us what you are trying to do - this may influence the use of brain cells

jack

I believe a DIY peristaltic pump like Richard suggested would be a good bet.

I have seen a mechanism to squeeze a syringe -- a bit of threaded rod and a stepper maybe. This might be another option, depending on how much, overall, material needs to be metered out.

Some things that might help would be to know if the material has any unusual properties -- high viscosity, temperature, corrosiveness. Any difficult cleanup requirements?

Another idea – I once heard of someone using old ink-jet print cartridges to squirt something other than ink. The interface on the cartridges – at least some brands — has been reverse engineered and documented.

You might be able to use a servo to squeeze something like the bulb of an eye dropper, or use it to control a small valve. You would need a setup for continous feed of the liquid, and small check valves. Check the aquarium supplies at walmart or petsmart for small airline valves, tubing, and check valves. A lot of variables control the actual size of drop produced.