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Open Source Chemical  Analysis [Everyone Welcome]

m.ratcliffe

A lot of us here are working on hydroponics or aquaponics, a lot of the sensors are outdated and it would be great to have more information about the growing fluid at our disposal. On this page it would be great if we could discuss general techniques and potential prototypes to measure all the things we feel are important in a growing fluid.

 

Aims, to make a cheap [sub $XXX] spectrometer[or other] capable of measuring the quantity of chemicals in a liquid:

>What is needed :

Automated Green House Blog:20.1 - Toying with Chemical Analysis - Essential Nutrients

 

What is bad and can accumulate:

> [Coming Soon]

>Other things we can think of

 

 

Types of sensing [this will grow larger I hope and each one will have its pro's and cons listed]

>IR Spectrometry

>UV Spectrometry

>Mass Spectrometer [Will build this later]

 

Other ideas:

>Change frequency of AC EC measurments, maybe we can see polarisation happen for each element at a certain frequancy.

>Charge a probe to +5 and measure its depletion curve. maybe there will be peaks at certain times as polarisation is reversed.

 

I know very little on this topic right now, but maybe with a few of use we can make it work.

 

 

Maybe we could share the load between us and each tackle a small portion of the problem each, ie write up a little about what we need to measure, each sum up a common technique used today and pro's/cons of automating it.

 

If anyone can think of a better place to house this discussion on Element14, please let everyone know. And could one of the admin tag everyone in it, so all of the other great contest content does not put it in their shadow.

 

Some Useful Links:

http://store.publiclab.org/products/desktop-spectrometry-kit-3-0

 

 

 

 

Message was edited by: Michael Ratcliffe Anyone can Alter the content, please leave a short summary here of the changes

 

Contributors:

 

DAB I cant find a way to link you, but do you want to join the project?

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  • Hi Michael,

     

    Do you have any kind of design in mind? I've read in places that people can achieve some results with a compact disc as the diffraction element, but an optical diffraction grating costs a bit : (

    It would be worth investigating astronomy resources, because they are interested in spectrometers too, and some people have constructed them using a grating, mirrors, optical slit and line CCD (lots on ebay) and appropriate circuitry. However, this is in the several hundred-dollars ballpark minimum (and more if experimentation is needed!). Those CCDs (probably intended for fax machines) are good for quite a large portion of spectrum. Specifying the grating, mirrors etc is a hard thing though without either experimentation (which could get expensive!) or maths, but I don't know any optics experts : ( Free optical simulation software is usually limited to a few elements, not enough to simulate the entire thing : (

    I have a few optics parts (with part numbers and specifications so it can be replicated) so I will try to see what I can do with them when I get some time, but it really will be guesswork to an extent for me image I purchased them in mind to experiment with building a spectrometer a long time ago, but the parts

    are with near-certainty sub-optimal since some of it was guesswork based on what I had read at the time, and what I could calculate (which was not much).

    There could be more unconventional methods that are cheaper to do, but I've not really investigated those.

  • in reply to shabaz

    Hi Shabaz,

     

    I have a few designs I'm working on my self but this thread is to get something that works, it doesn't matter If I like it or would have done it that way. If its works it works and we can all fine tune it as the project progresses.

     

    I would however like to try and keep it as simple as possible even at the expense of accuracy. I know very little on the subject at the moment, but with a bit of reading that can change.

     

    My designs all centre around no moving parts, the the main ones are:

    >Radio frequency attenuation [different elements will block RF if a certain way]

    >Polarisation characteristics [The fluid beocomes polarised, we may be able to get usable data from a polarisation curve]

     

    Not a lot of information in the above explanations, I will write them up after ive tried a proof of concept for them.

     

    It would be great is you could contribute at any level.

  • in reply to m.ratcliffe

    The RF attenuation method you refer to may work, but (just a minor point) maybe the thread needs a name change, because (I think) your aim is open source chemical analysis, and the spectrometer is just one way? Just a suggestion though - I don't have the answer : (

     

    As another idea to throw out there, there is an experimental way concerning impedance measurement. Linear Technology has some parts for this, at a low cost. Silicon Labs has some great oscillators that could be useful too. In essence the frequency is adjusted, and the response amplitude and phase is measured. It provides a 'signature' that you can record and compare with.

     

    I don't know of any good links to this (other than what is on the Linear site), but if I find any I'll post them here.

Reply
  • in reply to m.ratcliffe

    The RF attenuation method you refer to may work, but (just a minor point) maybe the thread needs a name change, because (I think) your aim is open source chemical analysis, and the spectrometer is just one way? Just a suggestion though - I don't have the answer : (

     

    As another idea to throw out there, there is an experimental way concerning impedance measurement. Linear Technology has some parts for this, at a low cost. Silicon Labs has some great oscillators that could be useful too. In essence the frequency is adjusted, and the response amplitude and phase is measured. It provides a 'signature' that you can record and compare with.

     

    I don't know of any good links to this (other than what is on the Linear site), but if I find any I'll post them here.

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