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Measuring Solar Radiation based on Photovoltaic Cells
So, the fun part will start now. Building the thing!
I'm not sure if the type of solar cells usually supplied with these type of devices are the best for your purposes, but of course, the best way to discover, is trying.
Just a hint: unless you are planning to put something over the solar panel of these garden lights, don't buy just one, because in less than a year the shiny surface of the solar panel will become almost opaque, and it will supply half the current.
MeteoCercal - Air Quality Data
Click here to watch at my ThingSpeak channel



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Hi,

(30-08-2017, 02:02)jgveill Wrote: This model seems to have a better solar panel (crystalline silicon), ... 

https://www.aliexpress.com/item/LED-sola...st=ae803_3

When I looked at that link two days ago, I think it said it has a Crystalline Cell with voltage (2v?), power/current rating and battery (600 mAh?) specified,  but I can't find any of those details in the "Product Details > Item Specifics" tab now.   Confused
EDIT: Ah, looking further down, those figures do appear after several other products. I wonder if they really do apply to that one? The Chinese are now even making "fakes" of some Chinese products. Wink

I have encountered a few low-cost solar garden lights with (Poly-)Crystalline cells, but the vast majority use Amorphous silicon.  However, as Werk implies, they're really only expected to run for a year if you're lucky.  A NiMH cell treated "kindly" may give around 500 charge-discharge cycles, but these are taken down into "deep discharge" every night, 365 times a year.    Sad

Personally, I'd start with one of the small crystalline 4 - 6 volt cells from Banggood such as this or this at just over $1 delivered (or a little more from a local Warehouse).

Cheers,  Alan.
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Thumbs Up 
Alan, 

I looked at your links and that's almost exactly what I tested few days ago that I bought from aliexpress.  The problem with that is to mount it.  You are right we see strange data ... Just below the picture we see ni-mh solar cell ?????  We may think it's the battery certainly better than other models using ni-cad. Protection level is IP65 which is excellent, and that's what I'm looking for.  Other models didn't indicate IP level.  Lower in the page we see more specs : crystalline silicon 2v / .08 watt.  This makes sense.  All othes similar lamps I've seen were 0.06w and much less expensive than this one. 

So I'll try ...  J Guy
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Hi.

It shouldn't be difficult to achieve IP65; just encapsulate the whole circuit in a "potting compound" or a surface treatment .  The batteries are often a soldered, wire-ended cell, so the only exposed component need be the switch.  That could be a magnetic reed switch, but probably not at a reasonable  price point.  However, encapsulation is no use if you want to "recycle" any of the components, or the enclosure.  Interestingly the "10 packs" of lamps on the same site, look very similar but are specified as Amorphous silicon panels and with a much lower IP rating.

The "crystalline" PV panels appear to be about 10 cm2, but that should deliver around 150 mW.  However, the crystaline PVs in the garden lights that I've seen have used just "slivers" (offcuts?) with a much smaller overall active area.  Also, don't expect too much from the batteries, they are often just "button" cells (which is generally sufficient for one day).

However, I did find two with a "real" AAA and AA NiMH cell in a "battery holder", so I could easily measure them in my charger/tester.  The AAA was marked 300 mAh (only about 1/3 of what's possible in that physical size) but actually measured 36 mA (yes ~12%), the  AA was marked 600 mAh (about 1/4 of what's possible) and actually measured ~50 mAh (yes < 10%).  Some Chinese specifications are no more than "think of a number".

Cheers,  Alan.
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You may be right that led lamp is not worth the price but I do not intend to use it.  I will remove everything but the solar panel.  You may also be right that it's not a real IP65 ... I'see in a few weeks.  For the batteries, I previously tested these chinese batteries.  I found exactly the same thing.  I asked for a refund and got it.  I will never buy any batteries from china.  

J guy
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Hello, I read you to prepare the best installation of PV and UV in something waterproof.
https://fr.aliexpress.com/store/group/3-...ea2aEGfgt4

there are domes of surveillance cameras, it behaves well in time.
What do you think?
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Hi,

It appears that those domes are made from Acrylic plastic (which is also known by the trade name "Plexiglass").

I happened to find this link which might be helpful.

It looks as if only the type "G UVT" would transmit (pass) the ~300 nm wavelengths which are the "correct" frequency to measure the "Official" UV Index.  But some "UV Index" sensors measure only UVA (around 350 nm) and "assume" that the UVB will correlate.

Cheers,  Alan.
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I will test with one of the dome of my cameras before ordering. thanks.
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(01-09-2017, 00:07)jgveill Wrote: You may be right that led lamp is not worth the price but I do not intend to use it.  I will remove everything but the solar panel.  You may also be right that it's not a real IP65 ... I'see in a few weeks.  For the batteries, I previously tested these chinese batteries.  I found exactly the same thing.  I asked for a refund and got it.  I will never buy any batteries from china.  

J guy


I forgot to come back ... NO it's not a real IP65 and even the solar panel looks bad.  So I bought a waterproof box with clear  and a 1,5v polycristaline solar panel.  When I received  the box, I checked the readings differences with and without clear cover for UV index and solar radiance. I saw lower readings but as the box was not fixed, angles were not exactly the same so I had problem to see the exact difference and decided it was good enough specially because with apogee clear sky I can calibrate solar irradiance.      

Here's the box : https://www.aliexpress.com/snapshot/0.ht...2808438610

here's the solar panel : https://fr.aliexpress.com/item/1-5V-Mini...0.0.0NxYK6

and here's the UV index sensor : https://fr.aliexpress.com/item/SI1145-UV...0.0.0NxYK6

Everything perfectly fits in the box.  I added spacers in the bottom to have the sensor and solar panel right under the cover.  I wanted to make tests with SI1145 wide spectrum capacity to extract solar radiance but I had problems with I2C library.  The first library I tried was not good at all, after some time sensor was reporting 0.  The Grove library is perfectly working.  Winter is here and readings are really low so ... next spring I will continue testing but so far so good. 

J guy
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"The SI1145 is a new sensor from SiLabs with a calibrated light sensing algorithm that can calculate UV Index. It doesn't contain an actual UV sensing element, instead it approximates it based on visible & IR light from the sun. "

Source: https://learn.adafruit.com/adafruit-si11...r/overview

Why not just use a sensor like the UVM30A or the VEML6075 which are designed to read in the UV spectrum?
These ones are supported by the WeatherDuino software, any others will require changes on the software, which may me a problem on every software upgrade.
MeteoCercal - Air Quality Data
Click here to watch at my ThingSpeak channel



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