Sandaysoft

Project Status Update.
The phototransistor with gain interface is a problem because of the very low photo current versus induced noise even if using screened cable.
Have found an alternative from Osram - SFH-5711 which have a logaritmic characteristic which I now think is exactly what is required.
It means for illustration that the signal level change is the same for the range 1 to 10 Lux as for the range 10000 to 100000 Lux.
Further I am now studying the so called 1-wire concept.
Maxim has a four channel A/D converter directly useable on a 1-wire system.
Only a 3-lead cable is required for 1-wire system (+5V, GND and data) meaning all the required electronics can be placed in the sensor unit itself.
In the PC end only a 1-wire/USB adapter is required (found one on http://www.hobby-boards.com/catalog/product_info.php?products_id=1503)

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The only snack about the photosensor is that it is only available in a SMT package 2,4 x 2,1 mm with four terminals.
So I need a good magnifying workshop lamp with light and the smallest possible tip for my solder iron (I am 67 and eyes have been better).
Best regards

Ole

Hi Ole
At 66 I find the same - I use a headband magnifier - a bit like a sun shield with lenses which I modified with a flip down jewellers eye glass for really close work. We just go to prove you don't lose the enquiring mind even if the other bits of the body don't work quite so well !!
I guess to get a good horizon to horizon line of sight a fairly high mast and long cables are neccessary (my mast is about 20 metres away above a barn roof to see over some trees) - would a wireless link for the data prove any better assuming the electronics can be built into the sensor. Or if in the end the data comes down to on or off could the sensor switch a 5V line ?
As I've said before my electronics knowledge is severly limited so that might be a completely useless idea.
Regards
Alan

Hi Allan.
Good to hear we both are 'products' of the last war - fringe benefits of our age is we don't have to interfere with the ugly phenomena called 'work' (as far as I remember thats the word ?)
I just briefly checked what is mentioned about maximum cable length for the 1-wire system.
Ordinary 4 leads telephone cable can easely achive 30 meters and using better cables like Cat-5 much longer length can work.
I am not still fully confident if 1-wire is the way to go, but it looks attractive in terms of simplicity just with a 1-wire / USB adapter in the PC end.
I do think that making a wireless link is a bit more complicated.

That is a possibility, but actually my plans for the software part is to display the results as shown in my entry of Mon Oct 26, 2009 3:31 pm which will also count the sunshine hours per day, week, month.
At present counting sunshine hours here in Denmark is not an urgent issue - rain counting is more popular.
Best regards
Ole

Hi Ole
I stll do a bit of work to keep the little grey cells working.
Maybe I'm oversimplifying but if you had a 'stopwatch' counting the on time during the 2.5 minute blocks (then reset) the software knows the date and time so your graph would still work.
On another subject I wondered about condensation misting up your glass jar.
Like Denmark Cornwall is grey and days seem short.
Regards
Alan

Hi Alan.
Fully agree on the grey cells - your genious idea combined with my knowledge of electronics and programming keeps them alive.

That is actually very precise what the software will do.

I have thought about that problem and I will make some small ventilation holes in the bottom plate where the glass jar is sitting.
I am still working on the design of the next prototype and I will send the drawing later.
Best regards
Ole

Hi Alan.
Attached shows record for the last hour of daylight to day (very grey and weet).
According Cumulus sunset was at 16:36 and dusk lasted untill 17:15
I have reduced the signal from the reflector by 50% just for illustrative purpose.
As seen the two signals follows each other quite nice which they also should do when no sun is present.
A perculiar issue is that the reflected signal is quite stable compared to ambient light - as it was raining during that periode I suspect that raindrops causes the fluctuations on the ambient signal.
A small amount of noise might also have an influence wherefore I will make a new electronic interface and put that up to the sensor - it will comprise the gain selector and a buffer amplifier to eliminate any induced noise.

The next exciting event will be some sunshine - next 5 days forecast says no.
By the way I have further studied the 1-wire system and I think it will be a bit to complicated (long personal learning curve) so I will stick to the present set-up with the USB A/D converter down and the mentioned electronics up.
Best regards
Ole

Thinking aloud ....

As there was no Sun, the reflector was 'seeing' a greater area of sky, so was effectively giving a true ambient level, whereas the 'ambient' sensor is looking at a smaller (non- Sun path) sector of sky, where variations in light level (because of the smaller sector) would be more noticeable - I think

_________________

......................Imagine, what you will KNOW tomorrow !

Certainly a better explanation than my raindrop theory.

Hi Allan,
Everything grey and weet here and will remain the same for the next 5 days according the mets.
I got a little help from the company Maxim IC in US and according what I now know it might not be so complex to go for the 1-wire solution as I thought initially.
As the 1-wire AD converter has 4 channels and so fare only two will be used, I have started to think about UV index measurements.
On snack here is that the protection glass must be a quartz type as ordinary glass works as an UV filter.
My next prototype includes the previous mentioned glass jar with glass bottom which have an outher diameter of 82mm
If we could find a glass tube instead (then open in both ends), I could place a lid on it which includes a quartz window.
Any good ideas on such a glass tube?
I have found a manufacturer in US called Express PCB - free download of schematic and PCB designer.
After PCB is designed, I can calulate the price including shipping.
4 PCB's for our project is total about USD 55 with an equal amount for shipping.
Do you any knowledge of a similar service in UK?
Best regards

Ole

Hi Ole
I came across www.technicalglass.co.uk who might help. They mention making products "to keep a production line going" which sounds to me as though they are prepared to make small quantities of components as replacements for things that get broken. I guess small quantities of pcb's are again uneconomic for most makers but www.p-m-services.co.uk sounded like a small enough company who might be interested.
The UV monitor sounds a good idea with people getting more concerned about skin cancer (here in Cornwall the air is very unpolluted and visitors here often underestimate the effect of the sun - a lot of very red people on the beaches). I would guess you'd only need a small window of quartz glass (maybe a tube) as the detector would need to see around 270 degrees of sky. I'm not familiar with UV detectors - can they be omnidirectional ?
Regards
Alan

Wow, I often drive past that PCB place - what a small world.

_________________
Nothing is foolproof, to a sufficiently talented fool . . .

WH1080PC Rochdale UK, 171m

Hi Keith
That could be handy - maybe Ole could let you have the details and you might be kind enough to call in and see what they could do - nothing like the personal touch.
Regards
Alan

Hi Alan,
Actually in the meantime I came across Acrylic cylinders which comes in many different diameters.
I also found out the acrylic should be very weather and UV ignorant so I think I will go for that in the next design.
I have also investigated a little bit more on UV sensors - there is a few available but the cost is relative high (around £ 30) and not to complicate the project I think we should leave that out until Sun Recorder MK2 pops up on the design desk.
PCB's: it is always a problem for us home-makers but is is almost impossible to handle the smalls chips.
I do have some friends in Chicago whom I have used as post forwarder before - the shipping from Express PCB within US is only $6 instead of $55 to Denmark. The problem with PCB's is always the initial set-up cost while the PCB itselt is not a costly issue (meaning ordering 3 or 10 does make a very big difference).
I might consider to make up a breadboard test of the 1-wire system before jumping into a PCB.
And: FINALLY SOME SUN SHINE
The attached graph shows the result.
My software used GMT + 2 hours (still on summertime) so the dawn was at 07:55 and sunrise was 08:34 on the scale - unfortunately I was not observing the sunrise itselft, but there was some fine clouds in that direction when I went up.
It seems that sun is reflected between 08:09 and 08:29 - that timing is not fully in line with the sunrise time - I think it might be caused by a higher refraction than normal.
Between 08:29 and 08:40 you see a drop - quite sure that a cloud was there.
My next plan is to have my digital camera remote controlled by the software taking a picture say every 1 min so I can establish a correlation to the data and the real life.
But up to now I think the data looks OK for our purpose.
Best regards

Ole

Hi Keith.
I checked some sample quotes on http://www.p-m-services.co.uk/ - prices looks very attractive compared to my US alternative and also compared to my professional experience here in Denmark.
I have attached a 1:1 size pdf drawing of the how the PCB is going to look although it is NOT the final design.
It would be great if you could just pop in and ask for a budgetary price.
Please also ask if they accept files in Protel format.
Best regards
Ole