Hi,
I am working on aquaculture project where I need to add fluid solution to water to measure its parameter(PH, Ammonia,...), thus I need to precisely add 2 or 3 drop of solution.
The scenario is I need to draw around 10ml of waters and add 2 or 3 drop of solution reagent and mix them and allow the color sensor to detect the color of the mixed solution.
I have look at micro pump, it's not enough to control up to droplet level.
Any idea to control this?
A linear actuator driving a syringe ?
Hi,
It sounds like a HSC chemistry class, where you do titrations to measure pH or certain levels of element and compounds in a mystery solution.
(I do hope they still do this chem prac, I did it back in the early 1970's, had to calculate the error in the final readings from equipment info and chemical specs.)
So I Googled;
Arduino titration
Interesting stuff, including a relatively competent Destructibles project.
They used a peristaltic pump.
It may give you some ideas.
Tom... 
i think syringe is too big and it's prone to problem after several usage. 2 drop of the solution is approx. 0.1ml which I don't think there's such a small syringe for this
@TomGeorge Based on the current technnology, we don't need to do this with PH, EC, ORP, there're cheap sensors available for this. But I am aimed at ammonia, nitrite and dissolved oxygen which is still very expensive with electronic sensors(NH3 is more than 400USD and only 1 year life time, N02 is more than 1000USD).
This will be an expensive project, no matter what route you choose. Precise control of titration requires well engineered equipment.
The Arduino forum is not the place to start looking.
It is not the size of the syringe that matters, it is the size of the aperture of the needle attached to it that matters
Is 0.09 ml/min slow enough for you? (that's the "max" rate at 5 rpm...so presumably even lower flow would be possible)
Only US$ 65........
Not sure if this is in the same level of accuracy that you need, but I have been playing with controlling droplets to photograph them when they 'splatter'. To release a drop I am using a solenoid valve (https://www.ebay.com.au/itm/313254747128) and programming a very short activation time (< 50 ms). I can consistently get a single drop to be produced.
Its not the sensors I was pointing out but the method and hardware.
You can get 0.5ml syringes, if you look at how long they are, you could probably get a small measured deflection to do the job.
You will not be measuring drops but volume, ml, so a calibrated syringe would be ideal.
Have you actually tried some of these methods, such as peristaltic pump, there are many different sizes.
Is there a reason for 10ml of sample, the larger the sample, the bigger the titration, the better precision.
Tom..
PS. Did the Google search give you any ideas?
Thanks, but solenoid valve or peristaltic pump have some inertia and other factor which we can't depending on the specific timeframe.
You are right, actually we need to measure the volume not drop. But at 0.1ml(two drops), it's very difficult.
Yes, maybe we can double the sample and so thus we can double titration, thanks.
Yes, I have thought of syringe too because it's accurate but I think it'll get clogged soon and also will need a servo and need regular maintenance. we need to do 2 test a day.
I think peristaltic pump is a good choice but it need to be used with another sensor(maybe pulse counter) in order to count the number of drop.
Yes, it's slow enough. But how do we make sure we can get two drops?
This is an interesting project.
For laminar flow the flow rate is determined by the dimensions of the tube, the viscosity of the liquid, and the pressure difference across it.
If you can use a very fine needle
and a small dP
you will get a very low flow rate
however fluid viscosity is very dependent on temperature so you would need to control that;
and also need to be able to turn on and off the flow.
You could pre-fill a syringe like this (or much larger ones) and drive them with a motor and screw mechanism to make a syringe pump. Or you could buy a syringe pump
As I know, syringe required frequent maintenance and get clog very soon.
Thus I am looking at peristaltic pump and another sensor to detect the number of drop instead.
BUT I HAVE NO IDEA WHICH SENSOR WHICH CAN DETECT THE NUMBER OF DROP FROM THE PUMP YET. I am searching for sonic or light sensor as to avoid touching the solution.
Have you tried asking Google to search for arduino drop counter? There are many hits, and @Grumpy_Mike posted a solution long ago.
My drop detector was from an article on plotting chaos published in 1994 about strange attractors being formed as the drip rate increased.
It involved a drip passing through an IR beam and being timed and counted.
These were the diagrams from it.
Thanks, thus we need to use Active IR?
Well it is one solution, however I don't know if your physical setup can produce the drops to flow through the air in order to count them. I suspect most of your problems will be mechanical ones.
Another solution that springs to mind is to have the drops fall onto a stretched rubber membrane and have a microphone count the sound of the drips. A bit like a drum.
I want it to fall from the air as I don't want to have anything to touch the solution so that it'll affect its chemical reaction and solution has strong chemical element.
My initial design will be a transparent bottle with 2 incoming pipes(1 for water(10 ml), 1 for the solution(1 to 3 drop, based on the type of solution)). It'll be a closed bottle as I need to use a vibration device to shake the bottle to mix the solution with the water. In such a case, will IR work?
