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Sunshine Recorder

For discussion of DIY weather equipment - sensors, accessories, improvements to existing kit etc
apenwith
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Sunshine Recorder

Postby apenwith » Fri Jun 05, 2009 1:18 pm

Hi
I mentioned in the Fine Offset forum that I was prototyping a McCleod type recorder and here it is. (don't laugh - it IS a prototype).
The white glass bulb (ordinary 2 quid bulb from B&Q) will reflect a spot of bright sun down the tube irrespective of the sun's position. The tube is roughly parallel to the earth axis. A Maplin's light detector circuit seems to work fine. The LDR is mounted in the end of the tube.
A little fine tuning and the circuit will turn on only when the sun is bright enough to cause a shadow. Not a bad definition of sunshine hours. I would like to be able to detect the on/off switch - perhaps via a serial port connection to the computer but that bit beats me as yet. An interim might be to use the relay to start/stop a battery clock.
The final version will look a bit smarter but the pic attached will give the general idea.
Any suggestions for improvement/computer linking etc would be welcome.
Regards
Alan
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beteljuice
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Re: Sunshine Recorder

Postby beteljuice » Fri Jun 05, 2009 5:25 pm

Am I missing something ?

Wouldn't the diameter of the 'collection' tube have to be >= than the bulb diameter, and / or have a convergence lense to the diameter of the sensor ?
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apenwith
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Re: Sunshine Recorder

Postby apenwith » Fri Jun 05, 2009 10:01 pm

Hi
No - angled up from the position of the LDR sensor the whole of the bulb is visible. The idea was to keep the tube diameter as small as possible to minimise extraneous light and create a greater sunshine/cloud contrast, So far it seems to work but the winter sun/cloud contrast might be more of a problem. For the ten pound (!) cost it looks quite promising but weatherproofing and finding a horizon to horizon site present more problems. If further tests look positive I'll post more but if anyone has a way of detecting an open or closed circuit via rs232 I'd love to know. I'd need a programme which (possibly) detects DTR and asociates that with the system clock. In the meantime I'll do some limited (pending site etc) tests with a battery clock.
regards
Alan

apenwith
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Re: Sunshine Recorder

Postby apenwith » Sat Jun 06, 2009 5:46 pm

Hi
Today was a perfect day to test the prototype - scattered cumulus (an omen ?) travelling fast in a brisk northerly and sun between.
I attached a cheap battery clock with a second hand to the light sensitive switch and - hey presto - the clock started a second or two after the sun caused shadows and stopped as the cloud obscured the sun and the shadows faded.
Next experiment is with a small light weight version that could be fixed to my mast without being too affected by the wind. Christmas baubles come to mind (but where are they in June ?) so the whole thing could be enclosed in a 3 inch by 8 inch transparent tube.
In answer to betelgeuse - the original Mcleod recorder did have a lens to project a circular image onto light sensitive paper but the light sensitive resistor operates as long as it see a reflection of the sun anywhere on the sphere.
I'd still appreciate a computer whizz to tell me how I can sense an on/off voltage - either RS232 or printer port - even better a simple circuit to send on/off data via usb.
Regards
Alan

apenwith
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Re: Sunshine Recorder

Postby apenwith » Tue Jun 09, 2009 12:25 pm

Hi
From the Heath-Robinson of the weather world.
The latest protoytpe version of the recorder head - very much miniaturised (see pound coin).
Initial tests (indoors with a bright light) seem positive. Next bright day will be the real test.
I'd still like a way of sensing the relay on/off via the computer and logging times - any help out there ???
Regards
Alan
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apenwith
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Re: Sunshine Recorder

Postby apenwith » Thu Jun 11, 2009 1:13 pm

Hi
The metallised globe didn't work - too many reflections from brightly lit clouds etc. So back to the white bulb but a smaller version - and now it seems ready for some field trials.
Not the best of days today with high overcast but enough sun to produce shadows - just.
The voltage balancing variable resistor is a bit fiddly - maybe a low v/resistor in series to give some fine tuning. The sensor head is attached with 25 metres of cable and still works fine.
I realised I didn't need to weatherproof the whole thing so the sensor tube is covered by a thin plastic cover. The relay starts and stops a watch - as it's only a twelve hour watch there could be a problem of deciding whether the sun shone N hours or 12 + N. As long as casting shadows is valid sunshine data I think this could work.
So attached is prototype Mk 3.
Regards
Alan
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apenwith
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Re: Sunshine Recorder

Postby apenwith » Sat Jun 13, 2009 8:34 am

Hi
Trials with my Mcleod type electronic recorder seemed to justify derigging my pole and
mounting the recorder head. I'm sure it's a possible solution though maybe it needs a more
sensitive voltage sensing circuit. I'm surprised I've not had more comments - or others
experimenting - as there were earlier sunshine recorder discussions on the forum.
Here's how it looks in situ.
Suggestions most welcome
Regards
Alan
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apenwith
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Re: Sunshine Recorder

Postby apenwith » Sun Jun 14, 2009 9:47 am

Hi
My last word on the subject.
It works - I can record bursts of sunshine as short as 5 seconds - I doubt the Campbell Stokes can achieve that.
If anyone tries the experiment using the Velleman (Maplin) light sensitive switch I'd recommend changing the 100 microfarad capacitor for a lower value (I used a 33 micro farad). It reduced the reaction time and made the adjustment of the light level much easier.
Here in west Cornwall (or anywhere) a headland or a hill can trigger off a line of cloud which affects one area and a couple of miles away the sky stays clear so sunshine recording is a bit meaningless - but I find it interesting or maybe it's just the challenge of finding a way to do it !
Regards
Alan

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beteljuice
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Re: Sunshine Recorder

Postby beteljuice » Sun Jun 14, 2009 10:39 am

:D Well done !

Please do keep us up-to-date with any observations / mods.

Any chance of a pic with an 'arrow' and / or lines on it to clarify its orientation both to earth axis and Sun path ?

I started a drawing then realised I was creating something too sensitive to scattered light, although changing the sensor 'gnoman' length or the 'reflector' diameter would alter its characteristics (I think) :?

diag.png
I was thinking a sensor on a skewer stuck in a poundland 'mirror ball', either being hung or positioned in a plant pot base :lol:
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......................Imagine, what you will KNOW tomorrow !

apenwith
Posts: 418
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Weather Station: w8681 BlakeLarsen Sun Recorder
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Re: Sunshine Recorder

Postby apenwith » Sun Jun 14, 2009 12:46 pm

Hi Beteljuice
Well maybe not quite the last word.
I thought about a mirror ball but if you mean the ones with a mirror mosaic stuck on I think
there would be too many gaps (judging by the sort of reflections they cast) and they would
probably reflect bright clouds as my metallised version did.
Having the ldr sensor in a tube means the ball and the tube itself shades out a lot of scattered
light. The white ball seems not to reflect white cloud light only an image of the sun.
The orientation is earth axis - about 40 degrees to the horizontal and pointing south (ie ball
north). The elevation angle is not critical as long as the rim of the tube doesn't shade out the
sun at its lowest (winter) angle.
I'm still using my watch as a timer (a bit fiddly soldering wires to the button cell contacts to
utilise an external battery) but I'd still like to find a computer interface to an on/off switch. HELP!
I may have to adjust the sensitivity for different seasonal sunlight strength although it might be
possible to compare ambient light by putting a LDR behind frosted glass (away from the sun)
and comparing that with the reflected light off the ball.
Just for interest - the cost in pounds - Light sensitive switch 6.95 - golf ball light bulb 1.00 -
watch (lidl) about 2.99 and a few bits of scrap aluminium.
Regards
Alan

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hans
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Re: Sunshine Recorder

Postby hans » Sun Jun 14, 2009 8:57 pm

looks like a very interresting project.
sunshine recording is what the fine/offset misses.

this is very promissing.
some ideas to help:
maybe a "stopwatch for pc"(google) might work,
there was one that also used the joystick connection (for on/off) (a normaljoystick uses microswithes)
also some make a csv-file for records,something for the programmers here.(maybe a small script in cumulus?) ;)

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steve
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Re: Sunshine Recorder

Postby steve » Sun Jun 14, 2009 9:11 pm

If you can work out a way to interface it to a PC, I'd certainly consider adding support for it to Cumulus. I'd also be tempted to build one myself - somewhat cheaper than the £250 for the Davis add-on for the VP2! I'd want a wireless connection, though ;)
Steve
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hans
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Re: Sunshine Recorder

Postby hans » Tue Jun 16, 2009 3:10 pm

well.not as easy as i thought,getting the data/signal to a pc.

did found a few schematics,but these are very old,intended for msx! and old printer connections,so no option.
most of the pc/laptops have usb.
i did find some for that, but they are not as cheap,as the intention was for this feature.
anyway,here i found some solutions,maybe it gives some people a starting point.

http://www.audon.co.uk/io8g.html

http://www.audon.co.uk/mypclab.html

http://www.farnell.com/datasheets/61216.pdf

http://www.lascarelectronics.com/pdf-usb-datalogging/data-logger0983706001196084444.pdf

skyewright
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Re: Sunshine Recorder

Postby skyewright » Tue Jun 16, 2009 4:19 pm

steve wrote:If you can work out a way to interface it to a PC, I'd certainly consider adding support for it to Cumulus. I'd also be tempted to build one myself - somewhat cheaper than the £250 for the Davis add-on for the VP2! I'd want a wireless connection, though ;)

I've not tried it myself, but what some people have done is 'hack' an Oregon temp/humidity (or temp only) unit, replacing the temp resistor with a light sensitive/dependent resistor.

No use to a VP2 owner of course, but wireless nonetheless. ;)
Regards
David

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steve
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Re: Sunshine Recorder

Postby steve » Tue Jun 16, 2009 4:55 pm

I do have a WMR928, but none of the external sensors seem to be working.
Steve
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