Arduino-powered Pipette Pump

I'm going to preface this by making it clear that I'm an alright programmer but have next-to-no knowledge of anything mechanical, so, I'll take any mocking and/or derision firmly in stride because I definitely deserve it.

This is a pipette pump. While you can't see it in the picture, the wheel is kind of like a gear, in that it has regularly spaced indentations which, I believe, would allow you to place a linear rod with equivalent indentations next to it to control the rate that it draws in liquid.

Leaving aside for a moment the calculations necessary to determine what fraction of a rotation corresponds to what volume of liquid and the force required to turn the wheel - I obviously plan to do that once I've got a better idea of what I'm going to need to do - does anyone have any ideas as to how to implement something like this?

It's obviously a small-scale project of no real significance but I'm interested in seeing if I can automate the most tedious part of my day to day. I'd like to be able to press one of three buttons, corresponding to 9ml, 1ml and 0.1 ml respectively - this much I actually know how to do - and have the pipette draw in that much fluid. The viscosity of the fluid isn't a factor as it's always essentially constant.

Like I said, I get electronics reasonably well, it's the 'making them move' part that's nontrivial.

Pipettor: This is a pipette pump. While you can't see it in the picture

What picture?

I know exactly what you are trying to build and I'm sure I could probably draw the missing picture. I've used one a thousand times. If you take it apart you'll find that the piston that moves up and down has teeth that mesh to the teeth in the wheel. What you want to do is somehow mount a stepper motor with teeth equivalent to what is on the wheel. With the stepper you'll be able to precisely control how far it moves. The difficult part is figuring out how to mount the stepper to the pipettor so that it isn't too unwieldy to handle. You'll have to figure out some sort of bracket to hang it on there. This may be a good time to learn a little about 3-D printing.

The other groovy part is that you could also program it so that for like 1 ml it could actually pull up 10ml and dispense in 1ml quantities for when you have to add 1ml of the same stuff to a whole bunch of tubes.

I'd be interested to see what you come up with.

BTW: If your organization has a little money these are commercially available. Check Fisher.

wvmarle: What picture?

I apologize, the picture did not load properly. It's kind of been a Very long time since I've used a traditional forum. Mea culpa.

https://imgur.com/a/hJ8Pr

Delta_G: I know exactly what you are trying to build and I'm sure I could probably draw the missing picture. I've used one a thousand times. If you take it apart you'll find that the piston that moves up and down has teeth that mesh to the teeth in the wheel. What you want to do is somehow mount a stepper motor with teeth equivalent to what is on the wheel. With the stepper you'll be able to precisely control how far it moves. The difficult part is figuring out how to mount the stepper to the pipettor so that it isn't too unwieldy to handle. You'll have to figure out some sort of bracket to hang it on there. This may be a good time to learn a little about 3-D printing.

Thanks so much for your reply. This was my intuition on the matter but, again, I know mechanical things about as well as I know classical german literature.

The other groovy part is that you could also program it so that for like 1 ml it could actually pull up 10ml and dispense in 1ml quantities for when you have to add 1ml of the same stuff to a whole bunch of tubes.

This is pretty much my main motivation for this, yeah. That's exactly what I do with it at the moment already, but manually.

BTW: If your organization has a little money these are commercially available. Check Fisher.

I figured that this already existed - I mean, it's too obvious of an idea not to. Unfortunately, at the moment, my 'organization' is a...to use the word lightly, college, at which I am a student. Particularly one that has contracted out its 'book store' - which also sells all scientific equipment - to the lowest bidder, and that means paying $300 for a $0.30 cent nylon bag, a box to put slides in, a pair of plastic safety glasses that falls apart three times / experiment and a pipette bulb. Had to buy the pipette pump mentioned above out of pocket. I Could go whole hog and buy a commercially available equivalent, but given I've got a bunch of Arduino and electronics stuff kicking around, cheap access to the city's 3D printer, and a working knowledge of solidworks, it seems like a decent project for my spare time.

Thanks so much for your answer!