Automatic Titration device

[markdem]

Hi All,

Just for fun, I have decided to start a project to try to automate one of the tasks I have with my aquarium and build a automatic titration device. However, I am having some problems working out the best way to go about building it.
Short description of how this thing works.

1. I have a bottle of aquarium water.
2. I have a bottle of red stuff.
3. I need to put 10mL (+/-.5mL) of aquarium water into a clear mixing container.
4. I then need to put .1mL(+/- .02mL) of red stuff into the container, wait and then put another .1mL in there until the aquarium water turns blue. The maximum amount I need of red stuff per test will be 1mL.
5. I then need to flush the clear container out.

Testing for colour change is no issue. That part is done. I do have issues with how to meter the liquids.
I was thinking of using some form of a 3 way valve and a syringe. The valve would take the red liquid from the bottle, the valve would switch and then the syringe would the be pushed forcing red stuff into the mixing container. Same would be done with another unit for the water.
Problem is, I can't find any valves with small (talking .1mm to .3mm) holes. If I use a valve that is 3mm, I will not be able to make sure all the liquid from the syringe will make it into the mixing container.

Does anyone know where I can get a valve like that. It needs to be rather cheep (<$50) and made out of plastic or some other material that will not rust. NO copper!

Or, does anyone have any other ideas of how I can do this?

Thanks

 

[BradtheRad]

Here is a method I've seen used to dispense a fixed amount of food to animals automatically.

A horizontal disk with a small indentation or cup. (You would make the volume .1 mL.)

A motor rotates the disk slowly all the way around once. The cup passes through the red stuff, and fills up.

The disk continues to rotate. The cup passes over the aquarium water, and it empties.

It would take work to make this mechanical device. You would need to create a good seal on the storage tank of red stuff, where the disk rotates against it.