Solar sensor

Thanks Pinto. I’ve found this other. It’s clear that a single solar cell and an ammeter is a basic pyranometer. The question is how to convert this analog signal to something PC and WD readable.

http://www.pages.drexel.edu/~brooksdr/DRB_web_page/papers/UsingTheSun/using.htm#design

You could use a 1 wire kit from www.hobby-boards.com and adapt it to a solar cell instead of the pin diode. WD can handle that. Or you could use just about any circuit connected to a labjack which WD can also handle.

Nice. I didn’t know about Labjack. Just a question: what should I have, an U3 unit and some driver and configuration software? Or am I missing anything?

Thanks.

I know WD can work with the U12 (that was the first one, their model numbers are going backwards :roll: ), but I’m not sure if the U3 has the same interface.

it works with that one too (that model replaces the U12)
(i think anyway)

Seem to be the same interface. Differences are:

U3 U12
16 analog inputs 8 analog inputs
20 digital i/o 20 digital i/o
2 analog outputs 2 analog outputs
2 counters 1 counter
2 timers no timer

Surprisingly U3 is cheaper than U12. I’ll try to make some tests, I think it’s the way to have a really cheap solar sensor.

.... would it be possible to make a solar sensor using these small solar cells?

That is exactly what’s been up on my roof for the past 18 months. See my “build” pictures here http://www.41south.net.nz/index.php?option=com_ponygallery&Itemid=74&func=viewcategory&catid=2

I interfaced them with a Hobby-Boards solar sensor PCB and it works an absolute treat :slight_smile:

If you would like any info on the mods involved I would be more than happy to oblige. You can get an idea of the solar graph produces from my 24/48hr graphs http://www.41south.net.nz/index.php?option=com_wrapper&Itemid=47

Thanks Colin, any comments will be appreciated.

My project is a bit different. I use a single 1v, 400 mA solar cell, horizontal positioned without diffusor. A variable resistor is fitted to provide some current graduation. I expect the Labjack U3 to arrive today, so I will test very soon. Here you can see the cell mounted on my “test bed” :slight_smile:

I keep working on it. Some days ago I found an excellent document about using solar cells as pyranometers:

http://www.chuck-wright.com/projects/pv-measure.html

With this info an some advice from Labjack forum, I think I have a working, solid pyranometer. Take a look at the below images. These have been today readings, on a cloudy day in the morning (especially between 11:15 and 12:00), and gradually clearing to a scattered winter sky, almost clear at the evening and dusk. Pic 1 shows solar radiation in the red plot (the other are from solar cells powering my home-made FARS). Pic 2 is the same, a bit clearer. Any comments about it will be welcomed.


Looks good!

Did you screw that into concrete 8O

Do you mean the base where it is fitted? No, it’s stone, granite. On a south window just to test, seeing the whole sun trajectory. But it is clear it would work better once in its definitive place with 360

Nice graphs, and thanks for that link.

Wow, for a test I would probably have used a clamp rather than drilling granite.

Not sure how much effect it has on the viewing angle but is it possible to take that plastic lens off the cell?

It’s been blowing up to 35 knots here today, so I want it secure :slight_smile:

The lens reason is that solar cell is not waterproof. It’s a crystal clear sealed protection. I think there’s no obstruction at all. Anyway, the final resistor adjustment has been made with it, so readings are not affected.

I was thinking of the effect of the lens on the viewing angle of the cell, which would affect the reading, especially at low sun angles.

I’ll check it tomorrow at daylight, and take some detail pics to post. I don’t think so, as the plastic lens lies directly on the cell’s surface.

Can this be adapted to a 1wire circuit?

With the 1wire boards I’ve seen, the photocell device is mounted on the circuit board. this brings up the question of weather tightness. With this setup the board could be mounted in a 2X4 or larger watertight encloser and cable going out to the sensor. Maybe?

You can extend the 1-wire photocell a short distance, although you have to supply your own wire.
This is obviously easiest to do if you are building it from the kit.
Personally, I would just buy a pre-built board with the moisture coating and a spare photocell,
they’re only a few bucks extra.

I wouldn’t try to save the existing photocell, but would just cut it off the board with some diagonal cutters,
and suck the lead ends and the solder out of the mounting holes with a solder sucker.
Then just solder in the new leads to the spare photocell.

Steve

I think you can protect the entire board as I did. Some silicone sealing on all joints and the cable hole. Mine has been outside for a month now, pouring down over the sensor, and nothing has happened.

Another graph showing a full sunny day (red plot). Created with DAQFactory and 10 seconds sample rate. WD still does not show this… or maybe I don’t know how to set it correctly.


Thanks for the info. Did I understand the Hobby-Board box or equivalent will work with a little sealant?

That would make life easier.