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i-Phos Budget Spectrometer

jaypeecee

jaypeecee

Member
Joined
21 Jan 2015
Messages
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Location
Bracknell
Hi Folks,

For those people who would like to know more about the spectrum of light being emitted from whatever aquarium lighting you own, the i-Phos Spectrometer is a great piece of kit. I've been using one of these for about a year and I wouldn't be without it. This is it:

http://chriswesley.org/spectrometer.htm?ref=DIYLightSpectrometerDescription5

It's basically a 40cm long tube with some optical components (including a webcam) inside it. And, it plugs into a USB port on your Windows PC. The only problem that I had when first setting mine up was webcam driver compatibility. I ran into problems on my old Dell laptop. But, my wife's old HP laptop (Windows 10) then came to the rescue. The i-Phos uses some software known as Theremino Spectrometer, which can be installed from:

https://www.theremino.com/en/downloads/automation#spectrometer

The guy that makes the i-Phos, Chris Wesley, is very helpful.

It is necessary to calibrate the i-Phos before use and the Theremino software has provision for this. It is possible to use a compact fluorescent lamp (CFL) - remember them? But, I bought a selection of seven LEDs that span the visible spectrum from 400nm - 700nm. More about these in a later post.

Attached is a sample spectrum from my setup.

And, finally, the price. It will set you back around £75. A bargain.

JPC

Blue_Sky_Door_Open_08.jpg
 
Nick72 said:
What units are measured in the y axis?
Click to expand...

Hi @Nick72

The y-axis is simply displaying relative intensity. It is without units as intensity would need to be measured with a PAR sensor and this would measure all light from 400 nm to 700 nm (or better). But, the spectrum tells us a lot about the light being emitted. For example, we can see how well aligned it is to the absorption spectrum or action spectrum of our plants. We can also see where there may be an excess of light that may promote algae or cyanobacteria.

Hope that helps.

JPC
 
Hi @Nick72

Following on from my reply above, it would also allow us to see which parts of the spectrum give our plants that extra 'zing' or make the colours 'pop'.

JPC
 
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Hi Everyone,

For the record, I want to make it clear that I have no commercial interests whatsoever in the i-Phos business being operated by Chris Wesley. Just in case anyone was beginning to have any suspicions. I am a customer just like any other customer.

JPC 🙂
 
Nick72 said:
How would you use this to see if you had excess light potentially causing algae?
Click to expand...

Hi @Nick72

There are several ways that I envisage. One would be to see how much light is being emitted in the green part of the spectrum. Plants reflect a large proportion of green light (that's why they appear green). But, the green part of the spectrum is also absorbed by a pigment known as phycoerythrin, which is used by BBA. And, BGA absorbs that part of the spectrum peaking around 610 nm (orange/red). So, an excess of lighting in these parts of the spectrum must surely promote unwanted BBA and BGA (cyanobacteria).

I cannot present adequate proof of my hypotheses as I simply don't have the resources to do so. But, I invite anyone who is sufficiently interested in this very important aspect of our hobby to at least give my thought experiments due consideration. And then, let's discuss it. If my hypotheses won't hold water (pun intended), I can live with that.

I'd also like to add that some people have observed an increase in algae and BGA/cyano since the advent of LED lighting where we previously would have had fluorescent tubes. Not only is the output/intensity of LED lighting (typically) higher than fluorescent lighting but I invite anyone to compare the spectra of these two lighting options. They are very different.

JPC
 
jaypeecee said:
I'd also like to add that some people have observed an increase in algae and BGA/cyano since the advent of LED lighting where we previously would have had fluorescent tubes.
Click to expand...
I was slow to adopt fluorescent tubes, still ran some of my tanks on incandescent bulbs until they were banned. I always seemed to get better plant growth with them, and no algae problems. Unfortunately, I don't know why that would be. 🙂
 
Hi Folks,

The attached image below shows the Absorption/Absorbance spectra for chlorophyll a, chlorophyll b and five pigments found in plants, algae and cyanobacteria. It doesn't show the response of the human eye; this peaks at around 565 nm and is a bell curve on each side of this wavelength with a 50% sensitivity at around 520 nm and 610 nm.

Pigment_spectra.jpg

I have not attached what is known as the Action Spectrum but there is a strong correlation between the combined absorption spectra of all pigments and the Action Spectrum. I have added the image above as it will hopefully help to make some sense of what I had posted earlier in this thread. The key word here is 'hopefully'!

JPC
 
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Hi...The i-Phos HD is an reasonable instrument for those of us who do not require a proficient unit to degree wavelength and one of the most excellent bargains I've found on the net for utilize in my laser pastime to date. At approximately 1/10 the taken a toll of a moo conclusion proficient unit, I don’t see how anybody who has to degree light wavelengths or ghastly transfer speed to a determination of approximately 2 nanometers from 370 to 950+ nm can go off-base at the cost advertised (When the computer program was legitimately calibrated I was able to degree precisely 1064 nm from a steady source through a 1 mm wide opening.
 
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