I need something that will let me dispense liquids in controlled amounts. I need to dispense anywhere from a single drop of water to maybe 10-20 drops, and in a separate mechanism, something to dispense up to 2 cups of water.
Where can I find parts for something like this?
If you mean very-controlled amounts, I'd say The Lee Company. They can be a bit pricey (I got a quote in the $60 range for a very small 5V dispensary solenoid, they probably have much higher), but they have everything from picoliter inkjet up to beverage quantities.
http://www.alltronics.com/cgi-bin/item/23U013/PMP/Papst-ECA-27.11-Peristaltic-(Wobble)-Pump
with a proper controller, i'm pretty sure this pump is pretty accurate. I remember seeing a similar one that claimed 70psi and fine accuracy, but i cant seem to find it. i think this one has less operating pressure.
(edit: hmm, i'm beginning to think this is the 70 psi one)
Would this little pump help at all:
Drug dispensers are usually something like a leadscrew driving a syringe plunger, but that might be just cause the drugs come in syringes for dispensing...
Maybe you can get some advice from this guy as featured on hackaday.
Gordon
If you don't want the liquid coming into contact with the pump, you could use a peristaltic pump. They work by squeezing a tube to force the fluid through. You can measure the flow rate by counting the revolutions of the motor. They come in a large asortment of sizes and flow rates.
Try http://www.aptinstruments.com/Merchant2/merchant.mv?Screen=CTGY&Store_Code=AI&Category_Code=P2
Maybe you can use a small normal pump and an eyedropper type nozzle, then let the drops fall past an optical sensor and count them. Does the larger volume need to be as accurate? Maybe you could use a scale to sense the mass of the fluid in the larger jar.