[loriz71]

Hi Werk
Can you send me the schematics for the Solar sensor. I've some problem to understand the way to amplify the signal from the photodiode.
Thank you very much

[werk_ag]

I really don't have a schematic for the Solar sensor.

The best I could do was to have published an extensive article about the whole process. Our member uncle_bob was translated it to English. The article is here.

Related signal amplification, I used a simple operational amplifier. See here.

I'm planning to have something like a ready made kit, but it can't be done before next summer, I need several clear sunshine days to calibrate each produced unit (every solar cell is different, and needs different amp gains).

[Live_Steam_Mad]

You have to build yourself the Solar and UV sensors for the WeatherDuino Pro2. Build the UV sensor it's easy, the Solar sensor it's a bit more complex. I wrote a long article on the subject, but it's written in Portuguese language. Maybe you can use google to translate it, and try to understand how it works. Anyway the article is here.
Maybe someone can translate it to English. 

I read the article using Google Translate and it worked very well for translating 99 per cent of it, I understood just about all of it. I see that in my part of the world (St.Helens, NW England, 12 miles from Liverpool), I have a Davis VP2 near by (at Irlam, Manchester) that I can refer to, that gives about 750 Wm^-2 in a fully sunny day in June. This is 750 Wm^-2 / 1300Wm^-2 = 0.577 of your readings in your area in Portugal. I would thus not be getting 130mV drop for Rsh (across the short circuit resistance which is needed) but only 130*0.577 = 75mV drop.

Also, if I was to measure the current through the PV panel by short circuiting the panel through my multimeter on a fully sunny day in June, I would get a proportionally lower value (75mA * 0.577) i.e. 43.27mA for Isc (short circuit current from PV Panel).

Since R = V/I, and since V is lower (75mV instead of 130mV) by the same proportion as I (43mA instead of 75mA for Isc), then both top and bottom of the equation are lowered by the same value, so it cancels out, and my Rsh needed will still be 1.733 Ohms, same as yours.

However my GAIN needed from my voltage measured from short circuiting the panel across Rsh will need to be higher to compensate for the smaller voltage due to less sunlight here, so I will need a gain of 11.92 (6.875 * 0.577), so my R1 and R2 for my op-amp circuit will have to be 4K Ohms and 47K Ohms. Hopefully I have this correct?

So as I see it, the only thing that changes from location to location is the gain needed and the resistances for R1 and R2 to be altered to suit this.

I have sent a PM asking for the little PCB that you are using for the op-amp.

Have you got a schematic for the op-amp circuit board that you can give us a link to?

I would like to know please what exact brand and model number of solar panel you purchased which you describe as being "1V - 100mW", or maybe you can give me a link to the Ebay auction that you got yours from?

I would like to know about the UV sensor next, have you got an article that you wrote about how to build that?

Best Regards,

Alistair G.

[Live_Steam_Mad]

Forgot to add, the above that I wrote is only valid if I use the exact same circuit and components and solar panel that Werk_AG used, whist altering only the R1 value. If I alter any of the components or if the solar panel has different characteristics, then I won't get a linear response in W/m2.

Regards,

ARG

[werk_ag]

So as I see it, the only thing that changes from location to location is the gain needed and the resistances for R1 and R2 to be altered to suit this.

Good to see you studied the matter...
but I think that a sensor must be constructed so as to be universal, and not depend on the location where it will be used, so it is good to build it capable of reading values up to a maximum of 1400 and 1600 W / m2

The only thing that can change the calculations are the solar cell characteristics, it's important to ensure that the R1 value maintain the cell in its linear region. This is what requires quite a few tests.
Unfortunately the solar cell (1V - 100mA) I had used in my prototype units is no more available. Now I'm doing tests with another type of solar cell, more easier to find.
I will give news ...

[Live_Steam_Mad]

Unfortunately the solar cell (1V - 100mA) I had used in my prototype units is no more available. Now I'm doing tests with another type of solar cell, more easier to find.
I will give news ...

I just found a 1V 100mA PV cell (Solar Panel) on Ebay ;-

http://www.ebay.co.uk/itm/6-Pcs-Polycrys...43d2f58aac

...would this be suitable for use, i.e. give very close agreement results compared with your original circuit where you were using your "1V - 100mA" solar panel?

Which exact solar panel are you using in your latest experiments? Got a link to it?

Regards,

Alistair G.

[werk_ag]

By the photos and specs they seems exactly like the ones I use on my sensor!

You are risking to have a reasonable solar sensor, spending only a few £ I like when people do home work and share it, so lets go...



For now, forget the greyed part of this circuit. The OP used is an AD822ANZ. Try to get an original IC from Analog Devices, avoid cheap chinese ones labeled only by AD822 (I had bad results with them).

OP output must not exceed 1.1Volt.
One more time, refer to published document about this matter, it's all there.

And for everybody... don't expect that I make calculations for you. I just can't do it.

"Give a man a fish and you feed him for a day; teach a man to fish and you feed him for a lifetime"

[uncle_bob]

I'm planning to have something like a ready made kit, but it can't be done before next summer, I need several clear sunshine days to calibrate each produced unit (every solar cell is different, and needs different amp gains).

Would it be possible to calibrate them against a known light source?
Do you know anyone with some bright lamps with a known spectrum?

[Live_Steam_Mad]

Right, well I've bought one of the Ebay Solar Panels as in that link I gave above, and I'll look forwards to doing the solar tests at some point in the future.

Last night I painted my FO radiation shield a pretty bright white since I didn't like the beige plastic absorbing sunlight and distorting the air temperature readings as much as it does, and whilst I was at it I also swapped over my wind cups (anemometer) for the darker ones that I just bought from Maplin in St.Helens (meant for the N96GY black version of the weather station, where I have the silver / black version N96FY), reason being my original wind cups made IMHO a quite noticeable (if not actually loud) irritating ticking sound from the magnetically triggered reed switch inside. The local St.Helens store has 5 of the darker colored ones in stock and I also bought one of the NF25R ones as well (also identical design, but much whiter plastic), they have one in stock, and I also have wind cups for my N96FY on order so I can have a spare.

The loudest ticking noise came from my original anemometer from my N96FY weather station (WH-1081), the medium loud ticking noise came from the one for the NF25R, and by far the quietest ticking sound came from the N96GY version made from the much darker grey plastic, so I installed the latter one as a quieter replacement for my original one.

I have very sensitive hearing and I could hear the ticking noise 20 feet away across the patio as I was observing last week with my C11 telescope. I also imagined that on a quiet warm night the ticking noise might not impress my neighbour through an open window. I have already been told off once by my neighbour on the other side for having my CG-5 telescope mount on it's fastest slew setting (a bit of a loud noise at night!) and had to turn it down to make it move slower and thus quieter. Don't want to annoy my neighbours.

Here are the links for the replacement parts from Maplin ;-

http://www.maplin.co.uk/p/maplin-replace...25fr-n76nf

http://www.maplin.co.uk/p/maplin-replace...96gy-n09qr

http://www.maplin.co.uk/p/maplin-replace...96gy-n81nf

http://www.maplin.co.uk/p/maplin-replace...96gy-n77nf

http://www.maplin.co.uk/p/maplin-replace...96gy-n78nf

http://www.maplin.co.uk/p/maplin-replace...96fy-n82nf

http://www.maplin.co.uk/p/maplin-replace...96gy-n80nf

...that last one is only if you have the compatible weather station. WDPro2 uses it's own sensors for temp. and humidity and transmitter, which replaces that last Maplin item.

I also noticed whilst I was in the shop that they had sold out of the new 200 GBP weather station with it's all-in-one suite of weather instruments and the color screen, otherwise known as the FO model HP1000 I believe, so it looks like someone in St.Helens or nearby area recently bought one. I notice that Maplin never sold the 3080, the 3080's bad reputation must have preceeded it...

My weather station setup outside can be seen here ;-

http://www.wunderground.com/personal-wea...ENGLAND609

...click on "about this PWS".

Regards,

Alistair G.

[Live_Steam_Mad]

OK so I just ordered the UV sensor (as shown here by Werk http://www.meteocercal.info/forum/Thread...er-station ) ;- off Ebay from China ;-

http://www.ebay.co.uk/itm/271479486164?_...EBIDX%3AIT

...6.65 GBP and free postage, a Gsens brand item code UVM-30A sensor mounted on a suitable PCB module,
and I have e-mailed 2 sellers to see if they have a genuine Analog Devices AD822ANZ part.

EDIT: one of the Chinese sellers replied and says "Yes! Same as picture!", so I have ordered 2 of them ;-

http://www.ebay.co.uk/itm/301222518099?_...EBIDX%3AIT

...at 2.43 GBP and free postage.

Regards,

Alistair G.