Alternative chemical sensors, such as webcam spectroscope

Charlie

rsevs3 wrote:

Just a bit of an update for anyone who cares about this.

I believe we all care... well I do, Im just not smart enough to add anything worth while. Great read though... I lurve experiments!

rsevs3

TBH Charlie the concept is easy. From there i just spend lots of time google-ing it. I think you would be plenty smart enough.

Having done a small amount of programming has helped in the last few days, but other than that i has been a case of start learning from scratch.

It is amazing how motivating lazyness is...

Bob H

rsevs3 wrote:

It is amazing how motivating lazyness is...

Gee whiz here all along I thought Lazyness was the Mother of Invention :wink:

BullwinkleII

re: RaspberryPi

!

35 $ for a pc on a credit card sized board with built in sound and high definition video

DrLuke

Just skimmed the whole thread. Will need to go back and read the references/links to catch up. Watching with interest.

I'm assuming nothing else that would likely be in the water is overlapping the absorption frequencies of ammonia etc. i.e the spectral curves are distinct enough that you won't require spectral unmixing.

If this is a stupid question just leave it and I'll find out when I get time go back and do the readings.

rsevs3

I am not really sure yet DrLuke. That is one of the big ones that will need testing. I am currently trying to work out hoe to read the HITRAN database which has the absorbance in a wide range of frequencies. I think... :lol:

I am waiting o. A few parts to arrive so I can start thinking about the physical online device. That will aid my development too. Currently I can calculate the absorbance over the entire spectrum. Then I will need to find/determine the molar absorbtivity and from that can calculate the concentration. I think that for a simple test like we are looking at we should be a let to just select a few frequencies.

Also in the to do list is set up a calibration system so I can calculate the wavelengths. At present I have not done anything that the spectral workbench can't do except for calculate absorbance which is easy enough. All I have done is worm out my own way of doing it and I'm am using python instead of processing.

Hopefully all that made sense. Been up for over 24hrs.

Sent from my GT-I9300 using Tapatalk 2

DrLuke

Makes sense.

My arduino and other stuff is sitting around doing nothing. Making robots etc is cool, but doesn't really serve a purpose for me, so would like to use it on something worth while/useful.

Hopefully I get some time so I don't look all talk.

BullwinkleII

I have no idea what the device is called or anything useful like that, but today my doctor put a clothes peg-like device on my finger.

It had a little LED display built right onto the peg and it measured my pulse, AND dissolved oxygen! She used words like infra-red when I asked how it worked.

I dont think she had a clue how it worked to be honest.

Sorry doc if you're reading this

It sure does make you feel like you are being cared for when you can get a blood O2 level without even being attached to that machine that goes PING!

It also might add to this discussion in some way, or at least bump this interesting project.

BullwinkleII

and...

A bossy nurse posted this link to my blog. It seems Arduino make a dissolved oxygen thinggy.

DO stamp..
http://www.amazon.com/dp/B0078WUJUO/ref=cm_sw_su_dp

Probe...
http://atlas-scientific.com/product_pag ... ensor.html

rsevs3

Thanks for the links BW.

Atlas Scientific has some cool stuff but the cost is up there. Yet another thing to add to the wish list...

creuzerm

I found this thread from Bullwinkle's blog. I read the whole thing and found it fascinating.

I am starting to use old android powered smart phones as computers with built in cameras. I found an app that gives the spectrograph. https://play.google.com/store/apps/deta ... learnlight 1 smartphone could be used to measure 2 different systems at the same time by alternating between the front and rear cameras.

I had thought about doing an intermittent pump to move water into the sampling area as I have cyanobacteria accumulation issues on any surface but than somebody mentioned sampling the water stream. Genius! Create a laminar flow (soda straws in an oversized section of pipe works I hear) with a square or rectangular orfice, and we have a nice, consistent stream of water to shine our light through.

Doing this in the right location in our system flow could also give us some insight into suspended solids and other parameters as well.

Bullwinkle, about your finger-clothes-pin - that works off of the hemoglobin in your blood for a reagent. It doesn't measure directly. http://en.wikipedia.org/wiki/Pulse_oximetry

But this brings up another point. What if we can use reagents that are organic that our system will consume after we introduce it for measurements? Like cabbage juice. A cabbage juice 'IV drip' to measure PH is simply fertilizing the system. Plus, we can grow our own test kit!

Keep up the good work. I've added this project to my list of projects to do.

creuzerm

So I've been doing some digging around, reading up on some of those links.

We need a white LED light, a diffraction gradient, a camera, and a computer to do this stuff. My android phone has all of these.

I also have a 3d printer & some old recordable CDs/DVDs. I am going to design a mobile phone based lab that uses the glassware that comes with the aquarium test kits that most of us probably already have.

I am thinking that making a box that you put in front of the phone's camera and flash, you can reflect light off of a CD/DVD piece at the back of the box. This should give you your minimum focal distance for the camera.

Every phone will need it's own design as the camera/flash geometry is different between phones. But if I design this right, I should just need to key in some measurements to the center of the lens and flash and let the computer sort out all the math for the reflector angle and such.

I am seeing 4 pieces that need to be made. The box & lid, a sample cover to block light from the vial sticking up & some sort of frame clip or case that holds & positions it correctly to the phone.

Do I put the slot before or after the water sample?
What am I missing? What don't I understand correctly? Ideas? Suggestions?

Ronmaggi

Those are the most useful first two posts I have ever seen! How do you measure ph with cabbage juice?

rsevs3

creuzerm it is cool to see someone else interest in this stuff.

Firstly, I dont think the CD will reflect the light as you think it will. To get the light back to the camera will require mirrors that are a concave shape i think.

You are a lucky person to have a 3d printer. I have been keeping my eye on them for a while and keeping an eye out for a good deal. It is worth a shot to see if you can get the light to reflect.

For the phone software, check out the publiclaboratory. Warren has just released an android app i think that may be of interest.

rsevs3

creuzerm wrote:

I had thought about doing an intermittent pump to move water into the sampling area as I have cyanobacteria accumulation issues on any surface but than somebody mentioned sampling the water stream. Genius! Create a laminar flow (soda straws in an oversized section of pipe works I hear) with a square or rectangular orfice, and we have a nice, consistent stream of water to shine our light through.

This was precisely my plan. I was reading about the square glass/quartz tubing you can buy as well, but it is slightly cost prohibitive.

I was also looking at buying a 3d printer to manufacture the parts to hold it all funnily enough.

My thought for processing were the raspberry pi though, reason being is that not everyone has a spare smart phone in the cupboard and you can also use a programming language of your choice, rather than just java.

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