DIY dosing pump

Just thought I would share some info and see if I could get some help.

Inspired by something I saw yesterday I tried making a homemade dosing pump, and it turned out to be fairly simple.

Basically you need an air pump, some sort of air-gang valve, a 2 liter bottle, and some airline tubing. You hook the air pump to some tubing, the tubing to the gang valve, then more tubing is connected to the other side of the gang valve and connected to the lid of the bottle with an air tight seal (so it is pushing air into the top of the bottle. Then you take another piece of airline tubing and put it in the bottom of the bottle, through the lid (air tight seal), and up to the tank that you are dosing stuff into.   Basically you use the air pressure from the air pump to push some sort of fluid up the line and into the tank. You use the gang valve to control how much fluid is being dosed.

One component I think would be needed is a inline one way valve that would keep the fluid from flowing back into the bottle if the pump were to turn off.


It seems like this would be a great way to drip kalk, or maybe add phytoplankton to a tank if you don't want to add it all at once.


What I was hoping to do with it though was to use it for dosing my balanced addatives. Is it possible to dose an accurate amount with an air pump? Also is there any way to get more fine tuned control with a gang valve?

Last but not least, anyone know where to get cheap inline one way valves?


Edited by Kevin - October 31 2006 at 10:39am

couple thoughts...

Ok, so I am tired of trying to test this thing so I just thought I would post it and see what everyone thought.

Here is a picture of what it is and how it works.


So basically you have a small motor that goes fairly slowly. On the little gear piece I made an acryic piece that fit and drilled holes in that piece for various dosing rates. Then I took a piece of steel rod (any rod will work) and bent it to stick in the hole, and bent the other end and hot glued it to the syringes plunger.

The syringe I fixed in place and on the end of the syringe I put a plastic T. One the other ends of the T's I put one way valves that flow the same way.

So here is the operation steps.
1. basically the motor rotates pulling the plunger out, witch creates a vacuum and pulls liquid up the line and into the syringe.
2. the motor continues to rotate pushing the plunger in. The fluid cannot go back down the line because of the one way valve so it continues up the line.
3. The process repeats and basically the fluid can never return down the line because of the one way valves.

I have done some testing with my 3 rpm motor and it produces very consistent results when operating at the same height from source to syringe to output.

Every 2 minutes on mine (trying to get syringe to use its full length) it would push about 4.1 ml of fluid. (If if was pushing the amount I thought it should it should have pushed 6 ml).

The things I don't know is how it will work over time. Namely, how long before the syringe wears out. How long before the one way valves stop working right.

Here is cost of supplies.
1. (1) 3 rpm motor -- $3.99 3 rpm motor (I know it says 2.5 rpm but that is what I bought and it is 3 rpm.)
2. (1) 1mm syringe -- $0.25 at calranch (or try a pharmacy)
3. (2) One Way Valves -- $2.00 -- One way valve
4. (1) Plastic T -- $0.99 from Home Depot for a pack of 5
5. Tubing -- I used rigid tubing hoping maybe it would make flow more consistant. I don't know if that makes a difference.

Also, you will need to figure out how to connect the tubing to the syringe, it is a loose fit with the tubing. I ended up using a larger piece of tubing on top of the syringe and other tubing to make a nice fit.

So in all the dosing pump would cost 7.25 not including the price of shipping and not including the price of a timer. I liked the idea of an electronic timer that would allow you to turn it off to within a minute but you could try and get it to dosing the amount you want on 15 or 30 minute intervals.

So let me know what you think.

Reinventing the wheel is just so much fun.

mark, how quickly does your tubing become too stiff/brittle dosing kalk via this method?

i've thought about dosing kalk as you are but figured that without some sort of chem resistant tubing the tube might become brittle and need replacing quickly, on the order of weeks at most...

-dwn

Thought I would give an update on this -- It half worked, and half didn't work.

The calcium portion worked just fine and I am sure if I still had it up and running it would continue to work. Unfortunatly the alk side did not stand the test of time. The problem is that the wants to precipitate out of solution onto everything. Well it did this inside of the one way valve and prevented it from doing its job, so the solution was sucked into the syringe, and then pushed back from where it came from instead of going up the tube.

I recently saw another post about using an air pump as a doser and I may play with that some more before I give in and do the peristaltic pump.

I messed around with several pumps and check valve schemes to pump water from my reservoir though my kalk reactor to the sump. It's switched on and off by a solenoid operated auto top off device. It's working fine now, but It would have been cheaper and I would have had a lot fewer mishaps if would have just bought a peristaltic pump in the first place. 

 

My kalk reactor is 3 ft tall and the main problems I had were:

Anyway, if you want to save yourself lots of headaches and aggravation, just get the peristaltic pump and be done with it. 

This company has several models: http://www.twopartsolution.com/index.php?main_page=index&cPath=26_31

Edited by gateb - May 02 2007 at 10:15pm