Re: [DIYbio] Re: DIY Plate Reader

[Otto Heringer]

This is not exactly what you looking for, but is probably a good framework to build the 96 wells plate for what you want to do:
http://www.iorodeo.com/content/12x8-led-array-96-well-microplates
http://www.iorodeo.com/content/microplate-holder-led-board

Em sexta-feira, 17 de julho de 2015 16:36:10 UTC-3, Sebastian escreveu:

If you use a photodiode as your sensor, remember its only as good as the power you feed it. You will need a very clean and stable voltage source (5v 3.3v, etc) so the ADC has a static reference. No matter how many bits of ADC accuracy you get, if you have a noisy power rail your signal to noise ratio will drop like a brick. There are many chips on the market that have integrated systems called transimpedence amplifiers but due to the miniaturization of the very high impedance gain resistor inside the chip itself Iv've found varied degrees of sensitivity across the same batch and identical part number chips. You can either spin your own PCB with a chopper amplifier  that has "zero-drift" and ultra-low noise or compensate for the variation in sensitivity. 

Ive built a few spectrophotometer prototypes for an upcoming publication with my research partner this fall (PLoS, nothing fancy) and have been doing some heavy reading on photodiode theory and practically own every kind of Light-to-X sensor where x is the modality (frequency, voltage, analog, digital, etc) from Mouser. There is no perfect sensor for the job. Also most of the light sensors, due to their chemistry, are biased toward the red/infrared side of the spectrum. Most white LEDs don't have a good full spectral range. Go for xenon lamps if you can, just be sure to cool them or they'll melt your enclosure.  Another thing is if you are reading multiple sensors at once, arduino may not be the best. We are switching to the Parallax Propeller system since it has 8 completely independent cpu cores at 80Mhz each. I don't know why more people don't use these little beasts in their projects.

Two books I'd recommend if you happen to go the photodiode route are:

-Photodetection and Measurement by Johnson

-Photodoide Amplifiers by Graeme

Also two very very good intro electronics books:

-The Art of Electronics third edition by Horowitz and Hill

-Practical Electronics for Inventors

Unfortunately I cant share my designs until we publish this fall, which will be open source, but I can offer you my two cents on the matter of spectrophotometery. Been wanting to make a plate reader and have some ideas as well but the need for it is not present in my current research goals. We can exchange notes later if you'd like. Good luck!

Sebastian S. Cocioba

CEO & Founder

New York Botanics, LLC

On Jul 16, 2015, at 4:51 PM, Abizar Lakdawalla <abi...@gmail.com> wrote:

A simpler approach is to use a android or apple tablet as an illuminator (many apps that provide bright RGBW colors, I use a free app called "Lightbox"). Place the plate on top of the tablet and then take a picture through an app, such as "ELISA Plate Reader" on Android. The App will then give you values for a 96 well plate. Enzo also has an ELISA reader app. You can also determine HSV values through most photo processing software such as GIMP or JImage. Jiamge already has a module for quantitation of grid images such as 96 well plates. For the photo softwares you just need  to take an image through a regular camera and import into the software. 

let me know if you need more details.

Thanks

Abizar

On Saturday, August 29, 2009 at 4:34:38 AM UTC-7, Inventoriffic wrote:

Hi,

I am planning on building a microplate reader for some experiments I
have planned. I'm just going to outline my plan to see if others have
some better ideas, or see folly where I don't :). It's been many years
since I was in biotech and I never went into the hardware side before.
I am using an arduino based platform for this.

1. Proof of concept Build basic prototype spectrophotometer
 - insert curvette's manually to switch between sample & controls
 - basic LDR + LED combo
 - no wavelength filter

2. Programmatic wavelength alteration for the basic spec
 - test a laser based light source
 - use a diffraction grating + servo to alter the wavelength of the
light source

At this point I will test the accuracy at a local lab.

3. Build prototype stepper motor based plate reader
 - designed so that I have control over x-y position + wavelength

My major question is around finding a good diffraction grating (or
alternative wavelength modifier) that I can control easily to get the
desired output wavelength. Any ideas? All criticism is helpful :)

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