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'[EE]: sunshine detector'
2000\12\20@165920 by P.C. Uiterlinden

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What 's the best way to make a sunshine detector?

The purpose of this detector is to control (via a PIC of course)
electrically actuated sun screens in front of a window of my house.

First question is: would I need two photo sensors (one "looking"  to the
sun, one looking in the other direction, so a differential measurement
can be made)? Or would one sensor suffice (by measuring the absolute
level of brightness)?

Second question: would a sensor in the visible light range be the best
choice, or UV (or perhaps even IR)?

I'm considering to do a first test with a TSL230 (Texas Instruments).
This device outputs a frequency proportional to the irradiance (visible
light), so interfacing to a PIC is straight forward.

Does anyone has experience in this field? Any suggestion is welcome.

Paul.

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2000\12\20@184305 by Chris Carr

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> What 's the best way to make a sunshine detector?
>
> The purpose of this detector is to control (via a PIC of course)
> electrically actuated sun screens in front of a window of my house.
>
> First question is: would I need two photo sensors (one "looking"  to the
> sun, one looking in the other direction, so a differential measurement
> can be made)? Or would one sensor suffice (by measuring the absolute
> level of brightness)?
>
> Second question: would a sensor in the visible light range be the best
> choice, or UV (or perhaps even IR)?
>
> I'm considering to do a first test with a TSL230 (Texas Instruments).
> This device outputs a frequency proportional to the irradiance (visible
> light), so interfacing to a PIC is straight forward.
>
> Does anyone has experience in this field? Any suggestion is welcome.
>
The angle of the sun above the horizon cannot be discounted as a parameter
if you intend controlling horizontal shutters. Think about physical geometry
before starting with the electronics. You may be able to construct a canopy
over the windows that will eliminate the need for electronics.

Heresy on PicList

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2000\12\20@204426 by Barry Gershenfeld

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>> What 's the best way to make a sunshine detector?
>>
>> The purpose of this detector is to control (via a PIC of course)
>> electrically actuated sun screens in front of a window of my house.

>The angle of the sun above the horizon cannot be discounted as a parameter
>if you intend controlling horizontal shutters. Think about physical geometry
>before starting with the electronics. You may be able to construct a canopy
>over the windows that will eliminate the need for electronics.
>
>Heresy on PicList

If you just want to know if the sun is out you could darned near
sense it thermally...

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2000\12\20@221515 by Tony Churchill

picon face
I recall from a greenhouse light measurement problem that one person had
used a simple photocell to measure the level of light. He housed it in a
transparent box and applied a coating (paint) to the box until he achieved a
satisfactory result. This was Omni-directional and apparently worked quite
well. If cost is a factor I suspect that this would be about as cheap as you
can find.

----- Original Message -----
From: "P.C. Uiterlinden" <spam_OUTpuiterlTakeThisOuTspamHACOM.NL>
To: <.....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU>
Sent: Wednesday, December 20, 2000 1:42 PM
Subject: [EE]: sunshine detector


> What 's the best way to make a sunshine detector?

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2000\12\20@223640 by Byron A Jeff

face picon face
>
> What 's the best way to make a sunshine detector?

Best is always subject to debate and seriously depends on the criteria.

>
> The purpose of this detector is to control (via a PIC of course)
> electrically actuated sun screens in front of a window of my house.

>
> First question is: would I need two photo sensors (one "looking"  to the
> sun, one looking in the other direction, so a differential measurement
> can be made)? Or would one sensor suffice (by measuring the absolute
> level of brightness)?

Depends on the application. And "looking to the sun" is a completely different
and more difficult activity. Essentially that's tracking.

Best guess is to start with absolute, see if it meets your needs, if not
then examine other strategies.

>
> Second question: would a sensor in the visible light range be the best
> choice, or UV (or perhaps even IR)?

Mine was visible light. I needed to control my outdoor lights.

>
> I'm considering to do a first test with a TSL230 (Texas Instruments).
> This device outputs a frequency proportional to the irradiance (visible
> light), so interfacing to a PIC is straight forward.

Well before you do that you may want to make a $5 electronics run and test
the real simple detector I put together. It consists of a 555 timer,
a CDR light sensitive resistor, and a handful of components. Essentially
it does the same as the TSL230, though not nearly as linear. In short
hook up the 555 in astable multivibrator mode with the CDR as R1 (the top
resistor connected between pins 7 and 8. The the frequency of the 555 will
depend on the amount of light shining on the CDR, the brighter it gets,
the faster it vibrates. BTW I found it useful to parallel the CDR with
a fixed resistor so that the slowest frequency can be capped.

BTW while I've never done it, this 555 action should be easily duplicated
using a couple of PIC pins. Consider.

 B0-------CDR-------+--R1--CAP------GND
                    |
                    B1

The following steps should get a proportional reading.

1) Make B1 an output and ground, discharging the cap. Make sure that R1 is at
least 20 ohms to limit the current through the PIC I/O pin.
2) Make B1 an input and B0 an output set to 5V. The cap will charge through
the CDR and R1 and will eventually register as a 1 on B1's input.

The length of time that it takes B1 to go from a 0 to a 1 is proportional
to the current resistance of the CDR which is coupled to the amount of light
shining on the CDR. Again you may want to parallel a somewhat high value
resistor with the CDR so that complete darkness doesn't take forever.

BTW has anyone had good luck with circuits like this?

With both of these techniques you will want to have hysteresis averaging
a bunch of samples and delaying a while after performing an action. I checked
for 20 seconds of consecutive light or dark readings with a mix causing
no action. Just reviewing my code (now two years old) I don't see the timeout
after switching for light and dark, just resetting the 20 second counts
for both light and dark.

It worked fine until my relay blew. I'm in the process of switching to
a time based system.

Hope this gives some insight into the process. I advise starting with the
simplest scenario, hardware, and software, and only refine it when it
doesn't meet your needs.

BAJ

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2000\12\20@224527 by David Huisman

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You could make a device to modulate the sun and then your system would only
respond to sunlight that is addressed to your house.

This would make it immune from interference from the moonlight, reflections
from passing satellites, "Star Wars" lasers, car headlights and kids with
torches.

Just kidding.

Merry Christmas everyone,

Regards

David Huisman

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2000\12\20@231325 by Dan Michaels

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>
>The purpose of this detector is to control (via a PIC of course)
>electrically actuated sun screens in front of a window of my house.
>

It may actually be easier than you think. Put the sensor "inside"
the house behind the movable sun screens - possibly in a box with
a diffuse translucent cover, pointed toward the window.

Feed sensor to a threshold comparator, and you'll never get more
light than you want. Change to a heat sensor, and you'll not
get more heat than you want.

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2000\12\20@232251 by Dale Botkin

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On Wed, 20 Dec 2000, P.C. Uiterlinden wrote:

> What 's the best way to make a sunshine detector?
>
> The purpose of this detector is to control (via a PIC of course)
> electrically actuated sun screens in front of a window of my house.

Paul,

I am thinking of the exact same thing for the miniblinds in my office.  In
the morning the sun shines directly into my eyes, but after it's past a
certain angle I want them open.

I was thinking of a light sensor at one end of a longish tube, set so that
sunlight hitting from a low enough angle would hit the sensor and start
closing the blinds.  As the sun rises further, the tube would put the
sensor in shadow and the blinds could be opened.  The PIC comes into play
because I think an R/C servo would make a dandy blind closer/opener.

Now that I really think about it, I'm thinking of maybe two of the
tube-and-sensor assemblies, one outside the blinds and one inside.  That
way I can just close the blinds enough to eliminate the glare, and open
them back up when the sun gets above the critical angle.

> First question is: would I need two photo sensors (one "looking"  to the
> sun, one looking in the other direction, so a differential measurement
> can be made)? Or would one sensor suffice (by measuring the absolute
> level of brightness)?

I have seen this method used to automagically flip rearview mirrors to
their anti-glare (up) position.  My old '88 Aerostar had it.

> Second question: would a sensor in the visible light range be the best
> choice, or UV (or perhaps even IR)?

Good question.  I'm thinking any of the above would work, but UV would
probably be less prone to false triggers from street lamps and car
headlights.  *I* don't care about that for my office, but you might.

> I'm considering to do a first test with a TSL230 (Texas Instruments).
> This device outputs a frequency proportional to the irradiance (visible
> light), so interfacing to a PIC is straight forward.

I hadn't thought much about the particular sensor to use, I'd figured
pretty much any photodiode, phototransistor or maybe even a CDS cell would
work.  Hey, maybe even a solar cell across a resistive load, driving the
PIC analog input...  how's that for overkill?  ;)

> Does anyone has experience in this field? Any suggestion is welcome.

No experience, but I'm wandering the same path, so maybe we can help each
other out.

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discoveries, is not "Eureka!" (I found it!) but "That's funny ..."
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2000\12\21@002908 by Gennette, Bruce

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Get a ldr (light dependant resistor) and measure its resistance in total
darkness(~10M), shaded room at noon(1 to 5M) and in sun light(~500R). Get a
trimpot resistor whos value is around the ldr's resistance in the shaded
room (typically 1M).

Wire them up as a voltage divider with +5V to one side of the trim pot, out
the centre leg, then through the resistor to 0V. A PIC input pin connects to
the junction of the 2 resistors.

Put the ldr in a tube and point it towards the window, towards a wall and
put your thumb over the tube to create different light conditions.  Set the
trim pot to its mid position.

When it is dark the high resistance of the ldr means that
10,000,000R/10,500,000R = 19/20ths of the +5V is lost in the ldr and 1/20th
lost in the trim pot, so the PIC I/O pin sees 4.75 which it interprets as a
Hi.  Current flow through the resistors will be 5V/10,000,500R = 0.49uA

When it is sunny the low resistance of the ldr means that 500R/500,500R =
1/1,001th of the +5V is lost in the ldr and 996/1,001th lost in the trim
pot, so the PIC I/O pin sees 0.005V which it interprets as a Lo.  Current
flow through the resistors will be 5V/500,500R = 9.9uA.  Warning - do not
turn the trim pot to 0R, because the current will increase to nearly 20mA!

Adjust the trim pot to get the trigger point you require.  Then measure the
resistance in the trim pot and substitute a fixed value resistor to reduce
cost.

What we have built here is a 1 bit analog to digital converter changing
light levels into a digital Hi or Lo.

You will need to debounce this VEEEERRRYYY SLLLLOOOWWW switch with software.
You'll also need some reality checking; if lots of small clouds are rushing
past you don't want the sun screens constantly openning and closing - put a
sun time=true minimum limit in your program.  Dark plastic filters over the
end of the sensor tube can help to dampen the swing too.

bye.

> {Original Message removed}

2000\12\21@045306 by Alan B. Pearce

face picon face
>Hey, maybe even a solar cell across a resistive load, driving the
>PIC analog input...  how's that for overkill?  ;)

Why use an analog input? Get an old solar powered calculator, and with a
suitable load resistor on the reclaimed solar cells you should be able to use it
as a digital input. I would think that the array of cells that seem to be in
these things should produce a logic high for 5v logic.

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2000\12\21@091118 by M. Adam Davis

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Making a sunshine detector is easy.  Put a light sensitive device (LDR,
phototransister/diode, etc) in the area you want to sense the sun in.

It sounds, however, as though your real desire is to measure either 1) the
angle of the sun, or 2) whether the blinds are keeping the direct sunlight
out.

Take two translucent film canisters, put a short wall between them, and
aim them at the sun (so the wall is perpendicular to the path of the
sun).  Depending on the height of the wall past the canisters, a given
angle of the sun will shine more light on one canister than the other.  If
you have LDRs (Light Dependant Resister, such as the venerable CDS cell
(Cadmium Sulfide?)) then you can measure the resistance and tell which one
is getting more light, which would give you angle of the sun within the
range of your detector.  You can use a resister divider from the LDRs
going to a comparaor if all you want is "The sun is within the angle of
interest, close the blinds" output.

-Adam

"P.C. Uiterlinden" wrote:
{Quote hidden}

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2000\12\21@173324 by J Nagy

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>> What 's the best way to make a sunshine detector?
>>
>> The purpose of this detector is to control (via a PIC of course)
>> electrically actuated sun screens in front of a window of my house.
>>
>> First question is: would I need two photo sensors (one "looking"  to the
>> sun, one looking in the other direction, so a differential measurement
>> can be made)? Or would one sensor suffice (by measuring the absolute
>> level of brightness)?
>>
>> Second question: would a sensor in the visible light range be the best
>> choice, or UV (or perhaps even IR)?
>>

       Our ELM337 was designed with this in mind (12C508 based). It uses a
single CdS cell to detect the presence of visible light but provides a 10
minute delay before changing states. This prevents someone's headlights in
the driveway  affecting your blinds or sprinkler system or whatever. If
you're using a PIC, it's easy to make delays this long.


       Jim Nagy
       Elm Electronics
 ICs for Experimenters
http://www.elmelectronics.com/

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2000\12\21@175020 by Peter L. Peres

picon face
A reliable sunshine detector can be made using a bolometer sensor. Nearly
all the other methods will react to fake light from street lighting,
thunder, advertising etc.

Automatic lights use a CdS sensor usually. They are pretty dumb and react
to birds and other obstructions.

I think that one can use a CdS photoresistor and a microprocessor to do
some filtering to remove the unwanted stimuli. I also think that using a
clock in the microprocessor to tell it when daylight should be there will
help a lot to avoid blinds closing when lightning hits in the middle of
the night or when passing cars illuminate the sensor for a few seconds at
night. Same for opening them because a bird is plucking its feathers while
sitting on the sensor. I am speaking from experience here. Three CdS
photoresistors in series, spaced out about 20 cm from each other in a
horizontal translucent (PE) tube oriented NS did it for me. Better incline
the tube to your latitude's sun angle away from the pole in your
hemisphere. The inclination helps dirt to slide off. I still had to do
some filtering and it used to be fooled by things like fireworks at night
and heavy clouds during the day. A CdS sensor can be used with the AN512
scheme.

Remember that exposure to strong light will cause a CdS to temporarily
change its Rdark.

Peter

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2000\12\21@184208 by Dale Botkin

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Thanks for all of the suggestions for sunlight sensors, but I think
what we're actually after is a *glare* sensor, something to tell when the
sun is not only present, but within a fairly narrow angle.  The best
suggestion I've seen so far was for the split-tube arrangement.

I hope to be able to try some of these some time after the first of the
year.  If I get the chance to do so, I'll post the results here, of
course.

Dale
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2000\12\26@170321 by P.C. Uiterlinden

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Byron A Jeff wrote:
>
> Paul Uiterlinden wrote:
> >
> > First question is: would I need two photo sensors (one "looking"  to the
> > sun, one looking in the other direction, so a differential measurement
> > can be made)? Or would one sensor suffice (by measuring the absolute
> > level of brightness)?
>
> Depends on the application. And "looking to the sun" is a completely different
> and more difficult activity. Essentially that's tracking.

Sorry, that's not what I meant with "looking at the sun". I merely tried to
depict the situation where one sensor is directly exposed to the sun, while the
other always is in the shade. In such a setup, if the sun is blocked by clouds,
each sensor would be illuminated roughly by the same amount of light.

> Best guess is to start with absolute, see if it meets your needs, if not
> then examine other strategies.

Yup, that's sound advice: stepwise refinement.


> > I'm considering to do a first test with a TSL230 (Texas Instruments).
> > This device outputs a frequency proportional to the irradiance (visible
> > light), so interfacing to a PIC is straight forward.
>
> Well before you do that you may want to make a $5 electronics run and test
> the real simple detector I put together. It consists of a 555 timer,
> a CDR light sensitive resistor, and a handful of components.

Hmm, interesting suggestion. It will be slightly cheaper than a TSL230. But
with the amount of dollars (or guilders in my case) I will save by building
all this my self, $5 or $10 dollar is not really the issue here.


> BTW I found it useful to parallel the CDR with
> a fixed resistor so that the slowest frequency can be capped.
>
> BTW while I've never done it, this 555 action should be easily duplicated
> using a couple of PIC pins. Consider.
>
>   B0-------CDR-------+--R1--CAP------GND
>                      |
>                      B1

This is also an interesting option. Only downside is that it costs an extra
IO pin.

Browsing through the application notes on the microchip site, I found several
notes describing similar setups (e.g. AN512, also suggested in another
mail in this thread).


> With both of these techniques you will want to have hysteresis averaging
> a bunch of samples and delaying a while after performing an action. I checked
> for 20 seconds of consecutive light or dark readings with a mix causing
> no action. Just reviewing my code (now two years old) I don't see the timeout
> after switching for light and dark, just resetting the 20 second counts
> for both light and dark.

I already have that covered in my software: the blinds will be shut after 3
minutes of continuous sunshine, and raised after 12 minutes of continuous no
sunshine. I copied those numbers from a description of a commercially available
sunscreen controller.

> It worked fine until my relay blew. I'm in the process of switching to
> a time based system.

That's too bad. Why not just replace the relay?

> Hope this gives some insight into the process. I advise starting with the
> simplest scenario, hardware, and software, and only refine it when it
> doesn't meet your needs.

Thanks for all the suggestions. Really appreciate it!

Paul.

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2000\12\26@170331 by P.C. Uiterlinden

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Dale Botkin wrote:
>
> I am thinking of the exact same thing for the miniblinds in my office.  In
> the morning the sun shines directly into my eyes, but after it's past a
> certain angle I want them open.

Apart from the reasons you mention, keeping the heat out is also
important
to me, also when I'm out.

> I was thinking of a light sensor at one end of a longish tube, set so that
> sunlight hitting from a low enough angle would hit the sensor and start
> closing the blinds.  As the sun rises further, the tube would put the
> sensor in shadow and the blinds could be opened.

In my situation that would result in a too narrow angle, I guess. What I
want is something like 180 degrees: if the sun shining at the front of
the house, shut the blinds. Therefore I was thinking putting the sensor
in
a little box with an opaque (milky) top (or perhaps even half of a table
tennis ball).

> The PIC comes into play
> because I think an R/C servo would make a dandy blind closer/opener.

And of course to build some timers. You wouldn't want the blinds to be
adjusted with every small cloud passing the sun.

> Now that I really think about it, I'm thinking of maybe two of the
> tube-and-sensor assemblies, one outside the blinds and one inside.  That
> way I can just close the blinds enough to eliminate the glare, and open
> them back up when the sun gets above the critical angle.

Too complicated for me, see above.

> > First question is: would I need two photo sensors (one "looking"  to the
> > sun, one looking in the other direction, so a differential measurement
> > can be made)? Or would one sensor suffice (by measuring the absolute
> > level of brightness)?
>
> I have seen this method used to automagically flip rearview mirrors to
> their anti-glare (up) position.  My old '88 Aerostar had it.

Interesting! About two months ago I drove a rental car in the US that
had
something similar. Only difference was that is was done all in solid
state
(LCD perhaps?). I noticed that the mirror went greenish when lit by
headlights from cars driving behind me. This was new to.

> > Second question: would a sensor in the visible light range be the best
> > choice, or UV (or perhaps even IR)?
>
> Good question.  I'm thinking any of the above would work, but UV would
> probably be less prone to false triggers from street lamps and car
> headlights.  *I* don't care about that for my office, but you might.

Me neither. Streetlights and car headlight will be too faint to trigger
the sensor anyway. If not, than discriminating between sunshine and
daylight
without direct sunshine would be impossible.

> > I'm considering to do a first test with a TSL230 (Texas Instruments).
> > This device outputs a frequency proportional to the irradiance (visible
> > light), so interfacing to a PIC is straight forward.
>
> I hadn't thought much about the particular sensor to use, I'd figured
> pretty much any photodiode, phototransistor or maybe even a CDS cell would
> work.  Hey, maybe even a solar cell across a resistive load, driving the
> PIC analog input...  how's that for overkill?  ;)

If that's what's lying unused in your toy box, it wouldn't be overkill
at all.

> > Does anyone has experience in this field? Any suggestion is welcome.
>
> No experience, but I'm wandering the same path, so maybe we can help each
> other out.

When I have something working you'll be the first (among several
thousands
others) to know. Via this awesome mail list, that is.    :-)

Paul.

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2000\12\26@170336 by P.C. Uiterlinden

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"Peter L. Peres" wrote:
>
> A reliable sunshine detector can be made using a bolometer sensor. Nearly
> all the other methods will react to fake light from street lighting,
> thunder, advertising etc.

I learn a new word each day (and forget at least the same amount).

From the follwoing URL:
http://www.britannica.com/bcom/eb/article/6/0,5716,82656+1+80503,00.html

bolometer
instrument for measuring radiation by means of the rise in temperature
of a blackened metal strip in one of the arms of a resistance bridge. In
the first bolometer, invented by the American scientist Samuel P. Langley
in 1880, a Wheatstone bridge was used along with a galvanometer that produced
a deflection proportional to the intensity of radiation for small deflections.
A later bolometer consists of four platinum gratings (each of which is made of
a series of strips) inserted in the arms of a resistance bridge; two of these
gratings, in opposite arms of the bridge, are placed one behind another, so
that the openings of one are opposite the strips of the other and are exposed
to the radiation, theother opposite pair being shielded; this arrangement
doubles the effect on the galvanometer and also compensates for any extraneous
temperature changes. Changes in temperature as small as 0.0001º C may be
detected in this way.

The spectrum bolometer consists of a single strip set on edge, in an arm of a
bridge. It is used for exploring the distribution of intensity of radiation
in a spectrum.

0.0001º C? Just a bit too insensitive for my application!    :-)

{Quote hidden}

A timer in software will take care of that: close blinds after 3 minutes of
*continuous* sunshine; raise blinds after 12 minutes of *continuous* absence
of sunshine.

Paul.

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2000\12\28@190111 by Peter L. Peres

picon face
>close after 3 minutes *continuous* sunshine

So if someone parks a car with the lights in your driveway and it stays
there for 3 minutes then the blinds close. Ok, maybe this makes sense.
Same for a thundercap making night out of day and opening the blinds just
in time to get dirt onto the windows from the first drops ;-)

The bolometers described by Britannica are metrology grade or whatever.
More everyday use bolometers are much more sensitive than the platinum
ones, because the innards are made of thermistor material. The reason a
bolometer will not be fooled by artifical sources (not easily) is the fact
that it measures the radiation intensity over a wide band of spectrum and
a wide solid angle (170 degrees is common). Since the sun is the strongest
source around by far (~1000W/m^2 on a sunny day at noon) it is easy to set
the trigger point such that only a Jupiter lamp at 5 meters will trigger
it falsely. Additionally it has a slow resonse so lightning and flashes
as well as cold light (streey lighting) will not impress it.

You could use a silicon detector instead if you would apply temperature
compensation and avoid its saturation in full light. Then the output
current would be proportional to incoming radiation flux and you could
have a set point wrt. this.

If I'd do this I'd use a 16C711 and an A/D or two and measure the peak
radiance over the last 7-8 days, median filter this, after making sure
that what I measured was indeed daylight (slow increase and decrease =
hefty low pass + median filter), and apply a trigger point expressed in
percent against this peak value. I'd also use a real time clock to
determine whether it's really day or night and have it override the light
trigger at certain times. The clock only needs to run in 10 minute ticks
and need not display realtime, so it counts binary in a register all by
itself. 24hrs = 1440 minutes = 144 10-minutes = 1(one) 8 bit PIC register.
;-)

Peter

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2000\12\30@002958 by Justin Richards

flavicon
face
Paul,

I have seen a variation of what you propose used for enabling solar panels
to track the sun.

They use a 4 quadrant photo detector (i believe readily available) in a
balanced bridge type of configuaration.  ie the bridge is balanced when the
sensor is looking directly at the light source and is identicle to the
circuit used in CD players to keep the laser aligned with the track.  As the
laser drifts off the track the intensity of the light reflected off the disc
is no longer evenly distributed across the detector the circuit is
unbalanced and a feedback circuit is used to return it to the balanced
condition.  This may hopefully be modified to suit your purpose.

Justin
{Original Message removed}

2000\12\30@174154 by P.C. Uiterlinden

flavicon
face
"Peter L. Peres" wrote:
>
> >close after 3 minutes *continuous* sunshine
>
> So if someone parks a car with the lights in your driveway and it stays
> there for 3 minutes then the blinds close. Ok, maybe this makes sense.

Hmm, in that case your headlights need some adjusting, especially when you
know my sunshine detector will be on the third floor...

[snip]

> Since the sun is the strongest
> source around by far (~1000W/m^2 on a sunny day at noon) it is easy to set
> the trigger point such that only a Jupiter lamp at 5 meters will trigger
> it falsely.

Yup, those were my thoughts too. I was wondering about what number to put
on the intensity of sunshine. Now I know: 1000 W/m^2, thanks. Interestingly,
the data sheet of a TSL230 (programmable light-to-frequency convertor) indicates
a linear characteristic to at least 100k uW/cm^2, which is 0.1 W/cm^2, which
is 1000 W/m^2.

So it seems I can get away by using only one sensor and measure the absolute
intensity of the sunshine, to get an indication whether the sun shines or not.

> You could use a silicon detector instead if you would apply temperature
> compensation and avoid its saturation in full light. Then the output
> current would be proportional to incoming radiation flux and you could
> have a set point wrt. this.

That will be my first try. If that won't work, than I always can add more
complicated stuff later on. Stuff like you mention below:

{Quote hidden}

Thanks for your response. If you don't mind, I'll stick to a TSL230 (which
should arrive by post any day now) and a 16F84.

Happy roll-over! (maybe politically not correct but well meant).

Paul.

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'[EE]: sunshine detector'
2001\01\02@120427 by Alan B. Pearce
face picon face
>So if someone parks a car with the lights in your driveway and it stays
>there for 3 minutes then the blinds close. Ok, maybe this makes sense.

I guess it could be that the daughters boyfriend doesn't want you watching :)

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