Driver to drive?

Phil Hobbs · Oct 29, 2015

On 10/29/2015 4:25 AM, Sylvia Else wrote:

Adding sci.electronics.design, which got left out by mistake.

On 29/10/2015 5:41 PM, Sylvia Else wrote:

I want to make something to detect whether there's direct sunlight
shining on particular place. I thought the obvious approach would be to
use a pair of light dependent resistors (LDR) - one located where it
will definitely be in direct sunlight (when the sun is shining) and
another that is at the location to be tested. Compare the resistances,
and the result should be clear enough.

But this means that at least one LDR will be in direct sunlight for
extended periods, and I can find nothing in the datasheets to indicate
whether the devices will survive that. My concern is UV degradation of
the encapsulation material.

I can put them behind glass, which will provide some protection, but
even then, they'll have to survive some UV.

Anyone have experience of this?

Sylvia.

Use a photodiode. Cheaper, better, more reliable, multiple sources.
For direct sunlight, something like an Everlight PD204-6C (19 cents in
qty 10) would work fine.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

pedro · Oct 30, 2015

On Thu, 29 Oct 2015 19:25:59 +1100, Sylvia Else
<sylvia@not.at.this.address> wrote:

Adding sci.electronics.design, which got left out by mistake.

On 29/10/2015 5:41 PM, Sylvia Else wrote:

I want to make something to detect whether there's direct sunlight
shining on particular place. I thought the obvious approach would be to
use a pair of light dependent resistors (LDR) - one located where it
will definitely be in direct sunlight (when the sun is shining) and
another that is at the location to be tested. Compare the resistances,
and the result should be clear enough.

Are you attempting to discriminate between "direct sunlight" and
diffues sunlight i.e. some cloud obscuration? If so I suspect the
LDR's may disappoint you.

Trevor Wilson · Oct 30, 2015

On 29/10/2015 9:01 PM, o pere o wrote:

On 10/29/2015 09:25 AM, Sylvia Else wrote:
Adding sci.electronics.design, which got left out by mistake.

On 29/10/2015 5:41 PM, Sylvia Else wrote:

I want to make something to detect whether there's direct sunlight
shining on particular place. I thought the obvious approach would be to
use a pair of light dependent resistors (LDR) - one located where it
will definitely be in direct sunlight (when the sun is shining) and
another that is at the location to be tested. Compare the resistances,
and the result should be clear enough.

But this means that at least one LDR will be in direct sunlight for
extended periods, and I can find nothing in the datasheets to indicate
whether the devices will survive that. My concern is UV degradation of
the encapsulation material.

I can put them behind glass, which will provide some protection, but
even then, they'll have to survive some UV.

Anyone have experience of this?

Sylvia.

Perhaps you can use a small solar cell as the transducer? These should
survive direct sunlight during some decades.

Some time ago we even purchased a calibrated one, which could be used
for absolute measurements. I had a quick look but was unable to dig up
more details on it...

**Best idea.

--
Trevor Wilson
www.rageaudio.com.au

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

Oct 30, 2015

In sci.electronics.design Sylvia Else <sylvia@not.at.this.address> wrote:

I want to make something to detect whether there's direct sunlight
shining on particular place.

The air conditioning in my 2001 Toyota uses a sensor in the top of the
dash, near the bottom of the windshield, to determine how hard to work;
more sun = A/C works harder. I have seen similar sensors in other
cars, starting in the early 00s.

The service manual says it's a photodiode and implies that the ECU
biases it with +5 V and expects to see 0 to +5 V in return; lower
voltages for more light on the sensor.

The reason I mention it is that for automotive, the design life these
days is probably 10+ years, and whatever it costs gets multiplied by a
volume of 10 to 16 million or so (in the US). So there are probably
good reasons why they picked a photodiode.

Matt Roberds

Xeno · Oct 30, 2015

On 30/10/2015 7:09 PM, mroberds@att.net wrote:

In sci.electronics.design Sylvia Else <sylvia@not.at.this.address> wrote:
I want to make something to detect whether there's direct sunlight
shining on particular place.

The air conditioning in my 2001 Toyota uses a sensor in the top of the
dash, near the bottom of the windshield, to determine how hard to work;
more sun = A/C works harder. I have seen similar sensors in other
cars, starting in the early 00s.

The service manual says it's a photodiode and implies that the ECU
biases it with +5 V and expects to see 0 to +5 V in return; lower
voltages for more light on the sensor.

The reason I mention it is that for automotive, the design life these
days is probably 10+ years, and whatever it costs gets multiplied by a
volume of 10 to 16 million or so (in the US). So there are probably
good reasons why they picked a photodiode.

Matt Roberds

Be able to get them cheap from the wreckers all ready to go given their
service availability. Test data should give you an idea of their biasing.

--

Xeno

George Herold · Oct 30, 2015

On Friday, October 30, 2015 at 2:30:26 AM UTC-4, Sylvia Else wrote:

On 30/10/2015 2:19 PM, pedro wrote:
On Thu, 29 Oct 2015 19:25:59 +1100, Sylvia Else
sylvia@not.at.this.address> wrote:

Adding sci.electronics.design, which got left out by mistake.

On 29/10/2015 5:41 PM, Sylvia Else wrote:

I want to make something to detect whether there's direct sunlight
shining on particular place. I thought the obvious approach would be to
use a pair of light dependent resistors (LDR) - one located where it
will definitely be in direct sunlight (when the sun is shining) and
another that is at the location to be tested. Compare the resistances,
and the result should be clear enough.

Are you attempting to discriminate between "direct sunlight" and
diffues sunlight i.e. some cloud obscuration? If so I suspect the
LDR's may disappoint you.

More between direct sunlight, and shadowed.

The project is to control a pivot-arm awning so that it extends only as
far as is required to prevent direct sunlight entering a window. The
window is almost exactly west facing, so the required extension varies
from none at all during half the day, to fully extended towards sunset.

I'm intending to put one sensor just below the window. The awning will
then extend until the sensor is in shadow, plus a bit. As the sun
moves[*] across the sky, the sensor will again be exposed, at which time
the awning will be extended further.

Sounds like you may want two sensors, so you can "see" when the
shadow of the awning cover the top one. (Perhaps that is already
your plane.)

George H.

Eventually the other sensor will indicate that there's no longer any
direct sunlight anyway, and the awning will be retracted.

Sylvia.

[*] Anyone wanting to point out that it's really the Earth that moves
will be ignored.

Jim Thompson · Oct 30, 2015

On Fri, 30 Oct 2015 17:30:16 +1100, Sylvia Else
<sylvia@not.at.this.address> wrote:

On 30/10/2015 2:19 PM, pedro wrote:
On Thu, 29 Oct 2015 19:25:59 +1100, Sylvia Else
sylvia@not.at.this.address> wrote:

Adding sci.electronics.design, which got left out by mistake.

On 29/10/2015 5:41 PM, Sylvia Else wrote:

I want to make something to detect whether there's direct sunlight
shining on particular place. I thought the obvious approach would be to
use a pair of light dependent resistors (LDR) - one located where it
will definitely be in direct sunlight (when the sun is shining) and
another that is at the location to be tested. Compare the resistances,
and the result should be clear enough.

Are you attempting to discriminate between "direct sunlight" and
diffues sunlight i.e. some cloud obscuration? If so I suspect the
LDR's may disappoint you.

More between direct sunlight, and shadowed.

The project is to control a pivot-arm awning so that it extends only as
far as is required to prevent direct sunlight entering a window. The
window is almost exactly west facing, so the required extension varies
from none at all during half the day, to fully extended towards sunset.

I'm intending to put one sensor just below the window. The awning will
then extend until the sensor is in shadow, plus a bit. As the sun
moves[*] across the sky, the sensor will again be exposed, at which time
the awning will be extended further.

Eventually the other sensor will indicate that there's no longer any
direct sunlight anyway, and the awning will be retracted.

Sylvia.

[snip]

Adrian Jansen · Oct 31, 2015

On 31/10/2015 2:10 AM, Jim Thompson wrote:

On Fri, 30 Oct 2015 17:30:16 +1100, Sylvia Else
sylvia@not.at.this.address> wrote:

On 30/10/2015 2:19 PM, pedro wrote:
On Thu, 29 Oct 2015 19:25:59 +1100, Sylvia Else
sylvia@not.at.this.address> wrote:

Adding sci.electronics.design, which got left out by mistake.

On 29/10/2015 5:41 PM, Sylvia Else wrote:

I want to make something to detect whether there's direct sunlight
shining on particular place. I thought the obvious approach would be to
use a pair of light dependent resistors (LDR) - one located where it
will definitely be in direct sunlight (when the sun is shining) and
another that is at the location to be tested. Compare the resistances,
and the result should be clear enough.

Are you attempting to discriminate between "direct sunlight" and
diffues sunlight i.e. some cloud obscuration? If so I suspect the
LDR's may disappoint you.

More between direct sunlight, and shadowed.

The project is to control a pivot-arm awning so that it extends only as
far as is required to prevent direct sunlight entering a window. The
window is almost exactly west facing, so the required extension varies
from none at all during half the day, to fully extended towards sunset.

I'm intending to put one sensor just below the window. The awning will
then extend until the sensor is in shadow, plus a bit. As the sun
moves[*] across the sky, the sensor will again be exposed, at which time
the awning will be extended further.

Eventually the other sensor will indicate that there's no longer any
direct sunlight anyway, and the awning will be retracted.

Sylvia.

[snip]

Interesting idea. My home office windows face west and the HOA rules
prohibit awnings. But I have interior (louvered) shutters that would
benefit from such an automatic control.

...Jim Thompson

For a fixed installation like this, you dont really need a sensor at
all. The suns location is completely calculable, all you need is the
date/time and location.

Get the time from a local clock or net server, set the location, and you
can do the geometry from the sun azimuth and altitude to get the angles
for control.

Jim Thompson · Oct 31, 2015

On Sat, 31 Oct 2015 10:20:59 +1000, Adrian Jansen <adrian@qq.vv.net>
wrote:

On 31/10/2015 2:10 AM, Jim Thompson wrote:
On Fri, 30 Oct 2015 17:30:16 +1100, Sylvia Else
sylvia@not.at.this.address> wrote:

On 30/10/2015 2:19 PM, pedro wrote:
On Thu, 29 Oct 2015 19:25:59 +1100, Sylvia Else
sylvia@not.at.this.address> wrote:

Adding sci.electronics.design, which got left out by mistake.

On 29/10/2015 5:41 PM, Sylvia Else wrote:

I want to make something to detect whether there's direct sunlight
shining on particular place. I thought the obvious approach would be to
use a pair of light dependent resistors (LDR) - one located where it
will definitely be in direct sunlight (when the sun is shining) and
another that is at the location to be tested. Compare the resistances,
and the result should be clear enough.

Are you attempting to discriminate between "direct sunlight" and
diffues sunlight i.e. some cloud obscuration? If so I suspect the
LDR's may disappoint you.

More between direct sunlight, and shadowed.

The project is to control a pivot-arm awning so that it extends only as
far as is required to prevent direct sunlight entering a window. The
window is almost exactly west facing, so the required extension varies
from none at all during half the day, to fully extended towards sunset.

I'm intending to put one sensor just below the window. The awning will
then extend until the sensor is in shadow, plus a bit. As the sun
moves[*] across the sky, the sensor will again be exposed, at which time
the awning will be extended further.

Eventually the other sensor will indicate that there's no longer any
direct sunlight anyway, and the awning will be retracted.

Sylvia.

[snip]

Interesting idea. My home office windows face west and the HOA rules
prohibit awnings. But I have interior (louvered) shutters that would
benefit from such an automatic control.

...Jim Thompson

For a fixed installation like this, you dont really need a sensor at
all. The suns location is completely calculable, all you need is the
date/time and location.

I abhor microprocessors... the world is ANALOG O>:-}

Get the time from a local clock or net server, set the location, and you
can do the geometry from the sun azimuth and altitude to get the angles
for control.

I like stand-alone systems. I'm the one responsible for the
"limp-home" ignition system in GM products. Those dumb-asses
initially wanted your car to drop dead if the timing failed and your
car's emissions went up.

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice

Sylvia Else · Oct 31, 2015

On 31/10/2015 11:48 AM, Jim Thompson wrote:

I abhor microprocessors... the world is ANALOG O>:-}

I confess that my planned implementation includes a PIC. There are some
issues to be dealt with - people walking in front of the sensor,
intermittent sunlight due to clouds, and the rapid changes that occur as
the sun intersects the extended plane of the wall. No doubt these could
all be handled using analogue circuitry, but using a PIC will make life
simpler - particularly as I have much more experience with software than
I do electronics.

Sylvia.

Carl Ijames · Oct 31, 2015

"Adrian Jansen" wrote in message
news:56340972$0$1596$c3e8da3$5496439d@news.astraweb.com...
For a fixed installation like this, you dont really need a sensor at
all. The suns location is completely calculable, all you need is the
date/time and location.

Get the time from a local clock or net server, set the location, and you
can do the geometry from the sun azimuth and altitude to get the angles
for control.
=============================================================

Build in a gps receiver and you've got time, date, location, and direction;
it's completely automatic, except for height above ground, I guess, if you
want to fine-tune those first and last few minutes of sunlight. They sell
those little gps usb receivers for what, under $40 qty 1, so cost to build
one into a moderate volume product has to be under $10. You could even add
a temp sensor so it automatically stays closed below some threshold to get
solar heat in winter.

-----
Regards,
Carl Ijames

Sylvia Else · Oct 31, 2015

On 31/10/2015 11:20 AM, Adrian Jansen wrote:

On 31/10/2015 2:10 AM, Jim Thompson wrote:
On Fri, 30 Oct 2015 17:30:16 +1100, Sylvia Else
sylvia@not.at.this.address> wrote:

On 30/10/2015 2:19 PM, pedro wrote:
On Thu, 29 Oct 2015 19:25:59 +1100, Sylvia Else
sylvia@not.at.this.address> wrote:

Adding sci.electronics.design, which got left out by mistake.

On 29/10/2015 5:41 PM, Sylvia Else wrote:

I want to make something to detect whether there's direct sunlight
shining on particular place. I thought the obvious approach would
be to
use a pair of light dependent resistors (LDR) - one located where it
will definitely be in direct sunlight (when the sun is shining) and
another that is at the location to be tested. Compare the
resistances,
and the result should be clear enough.

Are you attempting to discriminate between "direct sunlight" and
diffues sunlight i.e. some cloud obscuration? If so I suspect the
LDR's may disappoint you.

More between direct sunlight, and shadowed.

The project is to control a pivot-arm awning so that it extends only as
far as is required to prevent direct sunlight entering a window. The
window is almost exactly west facing, so the required extension varies
from none at all during half the day, to fully extended towards sunset.

I'm intending to put one sensor just below the window. The awning will
then extend until the sensor is in shadow, plus a bit. As the sun
moves[*] across the sky, the sensor will again be exposed, at which time
the awning will be extended further.

Eventually the other sensor will indicate that there's no longer any
direct sunlight anyway, and the awning will be retracted.

Sylvia.

[snip]

Interesting idea. My home office windows face west and the HOA rules
prohibit awnings. But I have interior (louvered) shutters that would
benefit from such an automatic control.

...Jim Thompson

For a fixed installation like this, you dont really need a sensor at
all. The suns location is completely calculable, all you need is the
date/time and location.

Get the time from a local clock or net server, set the location, and you
can do the geometry from the sun azimuth and altitude to get the angles
for control.

A practical difficulty is knowing by how much the awning has been
extended. Typical commercially available awning motors don't provide an
output indicating how much the barrel has turned, and even if they did,
the awning material stretches over time. One would really need to
implement something to measure the angle of the pivot arm. The light
sensor approach seems simpler.

Random image of a pivot arm awning:

<http://www.blindelegance.com.au/wp-content/gallery/pivot-arm-awnings/pivot-arm-awning-2.gif>

Sylvia.

krw · Oct 31, 2015

On Fri, 30 Oct 2015 08:09:49 +0000 (UTC), mroberds@att.net wrote:

In sci.electronics.design Sylvia Else <sylvia@not.at.this.address> wrote:
I want to make something to detect whether there's direct sunlight
shining on particular place.

The air conditioning in my 2001 Toyota uses a sensor in the top of the
dash, near the bottom of the windshield, to determine how hard to work;
more sun = A/C works harder. I have seen similar sensors in other
cars, starting in the early 00s.

Our cars use those sensors for lighting control but I don't think the
HVAC is tied in. A thermostat would seem to work better.

The service manual says it's a photodiode and implies that the ECU
biases it with +5 V and expects to see 0 to +5 V in return; lower
voltages for more light on the sensor.

The reason I mention it is that for automotive, the design life these
days is probably 10+ years, and whatever it costs gets multiplied by a
volume of 10 to 16 million or so (in the US). So there are probably
good reasons why they picked a photodiode.

Matt Roberds

John S · Oct 31, 2015

On 10/29/2015 3:25 AM, Sylvia Else wrote:

Adding sci.electronics.design, which got left out by mistake.

On 29/10/2015 5:41 PM, Sylvia Else wrote:

I want to make something to detect whether there's direct sunlight
shining on particular place. I thought the obvious approach would be to
use a pair of light dependent resistors (LDR) - one located where it
will definitely be in direct sunlight (when the sun is shining) and
another that is at the location to be tested. Compare the resistances,
and the result should be clear enough.

But this means that at least one LDR will be in direct sunlight for
extended periods, and I can find nothing in the datasheets to indicate
whether the devices will survive that. My concern is UV degradation of
the encapsulation material.

I can put them behind glass, which will provide some protection, but
even then, they'll have to survive some UV.

Anyone have experience of this?

Sylvia.

How about using an IR-transparent filter in front of the sensors?

Carl Ijames · Oct 31, 2015

But if it's winter you won't be extending it anyway, cloudy or not, so you
won't be "wrong". I guess you could argue extending it on a cloudy summer
day would be a waste, but I'm sure there would be a manual override if you
felt that strongly.

-----
Regards,
Carl Ijames

"Jim Thompson" wrote in message
news:21883b1fd2sa2bhil2pb7a3el3sa9qu5vo@4ax.com...

On Fri, 30 Oct 2015 21:28:35 -0400, "Carl Ijames"
<carl.ijamesXyZZy@ZZxyz.verizon.net> wrote:

"Adrian Jansen" wrote in message
news:56340972$0$1596$c3e8da3$5496439d@news.astraweb.com...
For a fixed installation like this, you dont really need a sensor at
all. The suns location is completely calculable, all you need is the
date/time and location.

Get the time from a local clock or net server, set the location, and you
can do the geometry from the sun azimuth and altitude to get the angles
for control.
=============================================================

Build in a gps receiver and you've got time, date, location, and direction;
it's completely automatic, except for height above ground, I guess, if you
want to fine-tune those first and last few minutes of sunlight. They sell
those little gps usb receivers for what, under $40 qty 1, so cost to build
one into a moderate volume product has to be under $10. You could even add
a temp sensor so it automatically stays closed below some threshold to get
solar heat in winter.

-----
Regards,
Carl Ijames

Except for a cloudy day >:-}

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice

Jasen Betts · Oct 31, 2015

On 2015-10-30, George Herold <gherold@teachspin.com> wrote:

On Friday, October 30, 2015 at 2:30:26 AM UTC-4, Sylvia Else wrote:
On 30/10/2015 2:19 PM, pedro wrote:
On Thu, 29 Oct 2015 19:25:59 +1100, Sylvia Else
sylvia@not.at.this.address> wrote:

Adding sci.electronics.design, which got left out by mistake.

On 29/10/2015 5:41 PM, Sylvia Else wrote:

I want to make something to detect whether there's direct sunlight
shining on particular place. I thought the obvious approach would be to
use a pair of light dependent resistors (LDR) - one located where it
will definitely be in direct sunlight (when the sun is shining) and
another that is at the location to be tested. Compare the resistances,
and the result should be clear enough.

Are you attempting to discriminate between "direct sunlight" and
diffues sunlight i.e. some cloud obscuration? If so I suspect the
LDR's may disappoint you.

More between direct sunlight, and shadowed.

The project is to control a pivot-arm awning so that it extends only as
far as is required to prevent direct sunlight entering a window. The
window is almost exactly west facing, so the required extension varies
from none at all during half the day, to fully extended towards sunset.

I'm intending to put one sensor just below the window. The awning will
then extend until the sensor is in shadow, plus a bit. As the sun
moves[*] across the sky, the sensor will again be exposed, at which time
the awning will be extended further.

Sounds like you may want two sensors, so you can "see" when the
shadow of the awning cover the top one. (Perhaps that is already
your plane.)

Paint part of the lower sensor black, put shade mesh in front of it,
(or fake that electonically) and a feedback loop that balances their
resistance will have the top sensor partly shaded.

--
\_(ă)_

Jim Thompson · Oct 31, 2015

On Fri, 30 Oct 2015 21:28:35 -0400, "Carl Ijames"
<carl.ijamesXyZZy@ZZxyz.verizon.net> wrote:

"Adrian Jansen" wrote in message
news:56340972$0$1596$c3e8da3$5496439d@news.astraweb.com...
For a fixed installation like this, you dont really need a sensor at
all. The suns location is completely calculable, all you need is the
date/time and location.

Get the time from a local clock or net server, set the location, and you
can do the geometry from the sun azimuth and altitude to get the angles
for control.
=============================================================

Build in a gps receiver and you've got time, date, location, and direction;
it's completely automatic, except for height above ground, I guess, if you
want to fine-tune those first and last few minutes of sunlight. They sell
those little gps usb receivers for what, under $40 qty 1, so cost to build
one into a moderate volume product has to be under $10. You could even add
a temp sensor so it automatically stays closed below some threshold to get
solar heat in winter.

-----
Regards,
Carl Ijames

Except for a cloudy day >:-}

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice

Ralph Barone · Oct 31, 2015

George Herold <gherold@teachspin.com> wrote:

On Friday, October 30, 2015 at 2:30:26 AM UTC-4, Sylvia Else wrote:
On 30/10/2015 2:19 PM, pedro wrote:
On Thu, 29 Oct 2015 19:25:59 +1100, Sylvia Else
sylvia@not.at.this.address> wrote:

Adding sci.electronics.design, which got left out by mistake.

On 29/10/2015 5:41 PM, Sylvia Else wrote:

I want to make something to detect whether there's direct sunlight
shining on particular place. I thought the obvious approach would be to
use a pair of light dependent resistors (LDR) - one located where it
will definitely be in direct sunlight (when the sun is shining) and
another that is at the location to be tested. Compare the resistances,
and the result should be clear enough.

Are you attempting to discriminate between "direct sunlight" and
diffues sunlight i.e. some cloud obscuration? If so I suspect the
LDR's may disappoint you.

More between direct sunlight, and shadowed.

The project is to control a pivot-arm awning so that it extends only as
far as is required to prevent direct sunlight entering a window. The
window is almost exactly west facing, so the required extension varies
from none at all during half the day, to fully extended towards sunset.

I'm intending to put one sensor just below the window. The awning will
then extend until the sensor is in shadow, plus a bit. As the sun
moves[*] across the sky, the sensor will again be exposed, at which time
the awning will be extended further.

Sounds like you may want two sensors, so you can "see" when the
shadow of the awning cover the top one. (Perhaps that is already
your plane.)

George H.

Eventually the other sensor will indicate that there's no longer any
direct sunlight anyway, and the awning will be retracted.

Sylvia.

[*] Anyone wanting to point out that it's really the Earth that moves
will be ignored.

Why not just sit down for an hour and derive the equations for the position
of the sun as a function of date and time and build your control system to
just move the blind to a precalculated position.

Jim Thompson · Oct 31, 2015

On Sat, 31 Oct 2015 00:28:30 -0400, "Carl Ijames"
<carl.ijamesXyZZy@ZZxyz.verizon.net> wrote:

But if it's winter you won't be extending it anyway, cloudy or not, so you
won't be "wrong". I guess you could argue extending it on a cloudy summer
day would be a waste, but I'm sure there would be a manual override if you
felt that strongly.

-----
Regards,
Carl Ijames

"Jim Thompson" wrote in message
news:21883b1fd2sa2bhil2pb7a3el3sa9qu5vo@4ax.com...

On Fri, 30 Oct 2015 21:28:35 -0400, "Carl Ijames"
carl.ijamesXyZZy@ZZxyz.verizon.net> wrote:

"Adrian Jansen" wrote in message
news:56340972$0$1596$c3e8da3$5496439d@news.astraweb.com...
For a fixed installation like this, you dont really need a sensor at
all. The suns location is completely calculable, all you need is the
date/time and location.

Get the time from a local clock or net server, set the location, and you
can do the geometry from the sun azimuth and altitude to get the angles
for control.
=============================================================

Build in a gps receiver and you've got time, date, location, and direction;
it's completely automatic, except for height above ground, I guess, if you
want to fine-tune those first and last few minutes of sunlight. They sell
those little gps usb receivers for what, under $40 qty 1, so cost to build
one into a moderate volume product has to be under $10. You could even add
a temp sensor so it automatically stays closed below some threshold to get
solar heat in winter.

-----
Regards,
Carl Ijames

Except for a cloudy day >:-}

...Jim Thompson

rickman · Oct 31, 2015

On 10/30/2015 8:48 PM, Jim Thompson wrote:

On Sat, 31 Oct 2015 10:20:59 +1000, Adrian Jansen <adrian@qq.vv.net
wrote:

On 31/10/2015 2:10 AM, Jim Thompson wrote:
On Fri, 30 Oct 2015 17:30:16 +1100, Sylvia Else
sylvia@not.at.this.address> wrote:

On 30/10/2015 2:19 PM, pedro wrote:
On Thu, 29 Oct 2015 19:25:59 +1100, Sylvia Else
sylvia@not.at.this.address> wrote:

Adding sci.electronics.design, which got left out by mistake.

On 29/10/2015 5:41 PM, Sylvia Else wrote:

I want to make something to detect whether there's direct sunlight
shining on particular place. I thought the obvious approach would be to
use a pair of light dependent resistors (LDR) - one located where it
will definitely be in direct sunlight (when the sun is shining) and
another that is at the location to be tested. Compare the resistances,
and the result should be clear enough.

Are you attempting to discriminate between "direct sunlight" and
diffues sunlight i.e. some cloud obscuration? If so I suspect the
LDR's may disappoint you.

More between direct sunlight, and shadowed.

The project is to control a pivot-arm awning so that it extends only as
far as is required to prevent direct sunlight entering a window. The
window is almost exactly west facing, so the required extension varies
from none at all during half the day, to fully extended towards sunset.

I'm intending to put one sensor just below the window. The awning will
then extend until the sensor is in shadow, plus a bit. As the sun
moves[*] across the sky, the sensor will again be exposed, at which time
the awning will be extended further.

Eventually the other sensor will indicate that there's no longer any
direct sunlight anyway, and the awning will be retracted.

Sylvia.

[snip]

Interesting idea. My home office windows face west and the HOA rules
prohibit awnings. But I have interior (louvered) shutters that would
benefit from such an automatic control.

...Jim Thompson

For a fixed installation like this, you dont really need a sensor at
all. The suns location is completely calculable, all you need is the
date/time and location.

I abhor microprocessors... the world is ANALOG O>:-}

So why are you using digital media to communicate? I wouldn't use a
microprocessor either. I'd use an FPGA, lol

Get the time from a local clock or net server, set the location, and you
can do the geometry from the sun azimuth and altitude to get the angles
for control.

I like stand-alone systems. I'm the one responsible for the
"limp-home" ignition system in GM products. Those dumb-asses
initially wanted your car to drop dead if the timing failed and your
car's emissions went up.

My dad had a new car that left him sitting more than once and they
couldn't find the trouble because it had cleared by the time they towed
it back to the shop. After the third or fourth time they cam out to
troubleshoot it in the intersection where it quit and found the trouble,
the ECU, of course. I think they sent it back to GM where they found an
output transistor was intermittently faulty. They had no way to detect
that sort of failure and self diagnose it. Seems like one more pin on
the connector and a wire back to an input would solve that problem for
system critical outputs.

--

Rick

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