Q. re: ratings for short circuit and open circuit

[Kris Krieger]

Well, this is sci.electronics.basics, so I have another basic question

I've been looking into buying solar cells, and I see a lot of this sort of
description:

"Square polycrystalline silicon solar cell has an output of .42V to .52V
(open circuit) and a current of >1.2amp (short circuit)."

What I'm wondering is, which one translates into how much the cell will
produce when it's all connected up in something like a light or motor or so
on? I'd assume that'd be "closed circuit", but better to ask and know,
than to assume.

Thanks in advance!

- Kris

 

[Tom Biasi]

"Kris Krieger" <me@dowmuff.in> wrote in message
news:Ldudnee3Sd8cixvVnZ2dnUVZ_oninZ2d@earthlink.com...

Well, this is sci.electronics.basics, so I have another basic question

I've been looking into buying solar cells, and I see a lot of this sort of
description:

"Square polycrystalline silicon solar cell has an output of .42V to .52V
(open circuit) and a current of >1.2amp (short circuit)."

What I'm wondering is, which one translates into how much the cell will
produce when it's all connected up in something like a light or motor or
so
on? I'd assume that'd be "closed circuit", but better to ask and know,
than to assume.

Thanks in advance!

- Kris

When you hook something up to it that's called loading it.
The specs you quote indicate the maximum the cell can supply.
If your load uses the spec voltage and draws less than the spec current you
are loading within spec of that device.

Tom

 

[Kris Krieger]

"Tom Biasi" <tombiasi***@optonline.net> wrote in
news:jPmdnZ6cgLpkhhvVnZ2dnUVZ_rHinZ2d@giganews.com:

"Kris Krieger" <me@dowmuff.in> wrote in message
news:Ldudnee3Sd8cixvVnZ2dnUVZ_oninZ2d@earthlink.com...
Well, this is sci.electronics.basics, so I have another basic
question

I've been looking into buying solar cells, and I see a lot of this
sort of description:

"Square polycrystalline silicon solar cell has an output of .42V to
.52V (open circuit) and a current of >1.2amp (short circuit)."

What I'm wondering is, which one translates into how much the cell
will produce when it's all connected up in something like a light or
motor or so
on? I'd assume that'd be "closed circuit", but better to ask and
know, than to assume.

Thanks in advance!

- Kris

When you hook something up to it that's called loading it.
The specs you quote indicate the maximum the cell can supply.
If your load uses the spec voltage and draws less than the spec
current you are loading within spec of that device.

Tom

OK, that makes sense - so the maximum voltage a cell can deliver (in
perfect sunshine) is X volts at a current (flow) of Y amps per hour.

Hmmm, so why do they specify (open circuit) and (short circuit)? I did
read these:
http://www.answers.com/topic/short-circuit
http://en.wikipedia.org/wiki/Short_circuit
but I still wonder why they can't just say "max current is Y amps" - are
they simply trying to indicate that, when they tested the item, it was only
connected back to itself, without any intervening components that might add
resistance, etc., that'd give the meter an incorrect reading? ((THe down-
to-bare-earth version of that last question being, Can I just ignore (open
circuit) and (short circuit) <g!&gt)

Thanks again!

- Kris

 

[Tom Biasi]

"Kris Krieger" <me@dowmuff.in> wrote in message
news:c4KdnegfEMbDqRvVnZ2dnUVZ_h_inZ2d@earthlink.com...

"Tom Biasi" <tombiasi***@optonline.net> wrote in
news:jPmdnZ6cgLpkhhvVnZ2dnUVZ_rHinZ2d@giganews.com:


"Kris Krieger" <me@dowmuff.in> wrote in message
news:Ldudnee3Sd8cixvVnZ2dnUVZ_oninZ2d@earthlink.com...
Well, this is sci.electronics.basics, so I have another basic
question

I've been looking into buying solar cells, and I see a lot of this
sort of description:

"Square polycrystalline silicon solar cell has an output of .42V to
.52V (open circuit) and a current of >1.2amp (short circuit)."

What I'm wondering is, which one translates into how much the cell
will produce when it's all connected up in something like a light or
motor or so
on? I'd assume that'd be "closed circuit", but better to ask and
know, than to assume.

Thanks in advance!

- Kris

When you hook something up to it that's called loading it.
The specs you quote indicate the maximum the cell can supply.
If your load uses the spec voltage and draws less than the spec
current you are loading within spec of that device.

Tom


OK, that makes sense - so the maximum voltage a cell can deliver (in
perfect sunshine) is X volts at a current (flow) of Y amps per hour.

Hmmm, so why do they specify (open circuit) and (short circuit)? I did
read these:
http://www.answers.com/topic/short-circuit
http://en.wikipedia.org/wiki/Short_circuit
but I still wonder why they can't just say "max current is Y amps" - are
they simply trying to indicate that, when they tested the item, it was
only
connected back to itself, without any intervening components that might
add
resistance, etc., that'd give the meter an incorrect reading? ((THe down-
to-bare-earth version of that last question being, Can I just ignore (open
circuit) and (short circuit) <g!&gt)

Thanks again!

- Kris
Sure you can just ignore it but its the info that you need.

When they specify open circuit voltage its saying that the device cannot
deliver more than that. When you load it you will get less.
The device has internal resistance. The internal resistance effects the
maximum current that can be supplied. With a short circuit (zero ohm load)
the internal resistance is such that the device cannot supply more current
than specified. Less than a short you can expect less voltage than open
circuit and less current than shot circuit.

Tom

 

[Kris Krieger]

"Tom Biasi" <tombiasi***@optonline.net> wrote in
news:dbGdnUzuRbk9qhvVnZ2dnUVZ_hzinZ2d@giganews.com:

"Kris Krieger" <me@dowmuff.in> wrote in message
news:c4KdnegfEMbDqRvVnZ2dnUVZ_h_inZ2d@earthlink.com...
"Tom Biasi" <tombiasi***@optonline.net> wrote in
news:jPmdnZ6cgLpkhhvVnZ2dnUVZ_rHinZ2d@giganews.com:


"Kris Krieger" <me@dowmuff.in> wrote in message
news:Ldudnee3Sd8cixvVnZ2dnUVZ_oninZ2d@earthlink.com...
Well, this is sci.electronics.basics, so I have another basic
question

I've been looking into buying solar cells, and I see a lot of this
sort of description:

"Square polycrystalline silicon solar cell has an output of .42V to
.52V (open circuit) and a current of >1.2amp (short circuit)."

What I'm wondering is, which one translates into how much the cell
will produce when it's all connected up in something like a light
or motor or so
on? I'd assume that'd be "closed circuit", but better to ask and
know, than to assume.

Thanks in advance!

- Kris

When you hook something up to it that's called loading it.
The specs you quote indicate the maximum the cell can supply.
If your load uses the spec voltage and draws less than the spec
current you are loading within spec of that device.

Tom


OK, that makes sense - so the maximum voltage a cell can deliver (in
perfect sunshine) is X volts at a current (flow) of Y amps per hour.

Hmmm, so why do they specify (open circuit) and (short circuit)? I
did read these:
http://www.answers.com/topic/short-circuit
http://en.wikipedia.org/wiki/Short_circuit
but I still wonder why they can't just say "max current is Y amps" -
are they simply trying to indicate that, when they tested the item,
it was only
connected back to itself, without any intervening components that
might add
resistance, etc., that'd give the meter an incorrect reading? ((THe
down- to-bare-earth version of that last question being, Can I just
ignore (open circuit) and (short circuit) <g!&gt)

Thanks again!

- Kris
Sure you can just ignore it but its the info that you need.
When they specify open circuit voltage its saying that the device
cannot deliver more than that. When you load it you will get less.
The device has internal resistance. The internal resistance effects
the maximum current that can be supplied. With a short circuit (zero
ohm load) the internal resistance is such that the device cannot
supply more current than specified. Less than a short you can expect
less voltage than open circuit and less current than short circuit.

Tom

Oh!

OK, great, thank you! I wrote that into my Notebook

- Kris

 

[Kris Krieger]

Tim Wescott <tim@seemywebsite.com> wrote in
newstidnfl_w5lFqxvVnZ2dnUVZ_tTinZ2d@web-ster.com:

Kris Krieger wrote:
Well, this is sci.electronics.basics, so I have another basic
question

I've been looking into buying solar cells, and I see a lot of this
sort of description:

"Square polycrystalline silicon solar cell has an output of .42V to
.52V (open circuit) and a current of >1.2amp (short circuit)."

What I'm wondering is, which one translates into how much the cell
will produce when it's all connected up in something like a light or
motor or so on? I'd assume that'd be "closed circuit", but better to
ask and know, than to assume.

Thanks in advance!

How much the cell will produce when it's all connected up depends on
your circuit and the amount of light shining on the cell.

They give you the two points you need to characterize the cell, and
expect you to work out a good compromise between optimum power and
circuit complexity.

Note that both of their points are zero-power points: .52V * 0A = 0W,
1.2A * 0V = 0W. The highest power point is somewhere in between
(_not_ at 1/2 voltage, alas, because a diode doesn't look like a
linear resistance), and the current (and possibly voltage, I dunno) at
which this 'best point' will occur varies with lighting.

Ah-ha... I worte that into my notebook, too. I'll have to give that some
more thought.

Thank you for the info

- Kris

 

[Tom Biasi]

"Kris Krieger" <me@dowmuff.in> wrote in message
news:0-6dnRnPkPIH2BvVnZ2dnUVZ_szinZ2d@earthlink.com...

"Tom Biasi" <tombiasi***@optonline.net> wrote in
news:dbGdnUzuRbk9qhvVnZ2dnUVZ_hzinZ2d@giganews.com:


"Kris Krieger" <me@dowmuff.in> wrote in message
news:c4KdnegfEMbDqRvVnZ2dnUVZ_h_inZ2d@earthlink.com...
"Tom Biasi" <tombiasi***@optonline.net> wrote in
news:jPmdnZ6cgLpkhhvVnZ2dnUVZ_rHinZ2d@giganews.com:


"Kris Krieger" <me@dowmuff.in> wrote in message
news:Ldudnee3Sd8cixvVnZ2dnUVZ_oninZ2d@earthlink.com...
Well, this is sci.electronics.basics, so I have another basic
question

I've been looking into buying solar cells, and I see a lot of this
sort of description:

"Square polycrystalline silicon solar cell has an output of .42V to
.52V (open circuit) and a current of >1.2amp (short circuit)."

What I'm wondering is, which one translates into how much the cell
will produce when it's all connected up in something like a light
or motor or so
on? I'd assume that'd be "closed circuit", but better to ask and
know, than to assume.

Thanks in advance!

- Kris

When you hook something up to it that's called loading it.
The specs you quote indicate the maximum the cell can supply.
If your load uses the spec voltage and draws less than the spec
current you are loading within spec of that device.

Tom


OK, that makes sense - so the maximum voltage a cell can deliver (in
perfect sunshine) is X volts at a current (flow) of Y amps per hour.

Hmmm, so why do they specify (open circuit) and (short circuit)? I
did read these:
http://www.answers.com/topic/short-circuit
http://en.wikipedia.org/wiki/Short_circuit
but I still wonder why they can't just say "max current is Y amps" -
are they simply trying to indicate that, when they tested the item,
it was only
connected back to itself, without any intervening components that
might add
resistance, etc., that'd give the meter an incorrect reading? ((THe
down- to-bare-earth version of that last question being, Can I just
ignore (open circuit) and (short circuit) <g!&gt)

Thanks again!

- Kris
Sure you can just ignore it but its the info that you need.
When they specify open circuit voltage its saying that the device
cannot deliver more than that. When you load it you will get less.
The device has internal resistance. The internal resistance effects
the maximum current that can be supplied. With a short circuit (zero
ohm load) the internal resistance is such that the device cannot
supply more current than specified. Less than a short you can expect
less voltage than open circuit and less current than short circuit.

Tom

Oh!

OK, great, thank you! I wrote that into my Notebook

- Kris
Keep in mind that power producing devices are usually specified with some

load applied. They chose the loads we have discussed. I bet you can find a
curve describing the characteristics of your device under different light
conditions vs loads. Look and see.

Tom

 

[Kris Krieger]

"Tom Biasi" <tombiasi***@optonline.net> wrote in
news:TqCdnSEHksrg4BvVnZ2dnUVZ_umdnZ2d@giganews.com:

"Kris Krieger" <me@dowmuff.in> wrote in message
news:0-6dnRnPkPIH2BvVnZ2dnUVZ_szinZ2d@earthlink.com...
"Tom Biasi" <tombiasi***@optonline.net> wrote in
news:dbGdnUzuRbk9qhvVnZ2dnUVZ_hzinZ2d@giganews.com:


"Kris Krieger" <me@dowmuff.in> wrote in message
news:c4KdnegfEMbDqRvVnZ2dnUVZ_h_inZ2d@earthlink.com...
"Tom Biasi" <tombiasi***@optonline.net> wrote in
news:jPmdnZ6cgLpkhhvVnZ2dnUVZ_rHinZ2d@giganews.com:


"Kris Krieger" <me@dowmuff.in> wrote in message
news:Ldudnee3Sd8cixvVnZ2dnUVZ_oninZ2d@earthlink.com...
Well, this is sci.electronics.basics, so I have another basic
question

I've been looking into buying solar cells, and I see a lot of
this sort of description:

"Square polycrystalline silicon solar cell has an output of .42V
to .52V (open circuit) and a current of >1.2amp (short circuit)."

What I'm wondering is, which one translates into how much the
cell will produce when it's all connected up in something like a
light or motor or so
on? I'd assume that'd be "closed circuit", but better to ask and
know, than to assume.

Thanks in advance!

- Kris

When you hook something up to it that's called loading it.
The specs you quote indicate the maximum the cell can supply.
If your load uses the spec voltage and draws less than the spec
current you are loading within spec of that device.

Tom


OK, that makes sense - so the maximum voltage a cell can deliver
(in perfect sunshine) is X volts at a current (flow) of Y amps per
hour.

Hmmm, so why do they specify (open circuit) and (short circuit)? I
did read these:
http://www.answers.com/topic/short-circuit
http://en.wikipedia.org/wiki/Short_circuit
but I still wonder why they can't just say "max current is Y amps"
- are they simply trying to indicate that, when they tested the
item, it was only
connected back to itself, without any intervening components that
might add
resistance, etc., that'd give the meter an incorrect reading?
((THe down- to-bare-earth version of that last question being, Can
I just ignore (open circuit) and (short circuit) <g!&gt)

Thanks again!

- Kris
Sure you can just ignore it but its the info that you need.
When they specify open circuit voltage its saying that the device
cannot deliver more than that. When you load it you will get less.
The device has internal resistance. The internal resistance effects
the maximum current that can be supplied. With a short circuit (zero
ohm load) the internal resistance is such that the device cannot
supply more current than specified. Less than a short you can expect
less voltage than open circuit and less current than short circuit.

Tom

Oh!

OK, great, thank you! I wrote that into my Notebook

- Kris
Keep in mind that power producing devices are usually specified with
some load applied. They chose the loads we have discussed. I bet you
can find a curve describing the characteristics of your device under
different light conditions vs loads. Look and see.

Tom

I don't have a device in-hand; I'm still messing around with the "design
a high-brightness Solar Light" idea, and as I keep reading, I keep coming
up with new questions (I can find a lot of answers via internet
searches, but not all.)

I had started off wanting to use 4 ICs, based upon what I'd found at the
Maxim website; they have a lot of example application circuits, three of
which would let me do what I want, however, when I added up all of th
esub-components, it was just too expensive. So now I'm rethinking
everything. For example, today I'm Googling to find out whetehr a
capacitor's "outflow" can be regulated such that it acts as a battery
(and how much it'd cost). I'm interested as a matter of curiosity in
addition to what I want to do.

Well, at least it keeps me out of trouble !

Thanks again,

- Kris

 

[Kris Krieger]

ehsjr <e.h.s.j.r.removethespampunctuation@bellatlantic.net> wrote in
news:nOcik.20$vu.8@trndny05:

Kris Krieger wrote:
"Tom Biasi" <tombiasi***@optonline.net> wrote in
news:TqCdnSEHksrg4BvVnZ2dnUVZ_umdnZ2d@giganews.com:


"Kris Krieger" <me@dowmuff.in> wrote in message
news:0-6dnRnPkPIH2BvVnZ2dnUVZ_szinZ2d@earthlink.com...

"Tom Biasi" <tombiasi***@optonline.net> wrote in
news:dbGdnUzuRbk9qhvVnZ2dnUVZ_hzinZ2d@giganews.com:


"Kris Krieger" <me@dowmuff.in> wrote in message
news:c4KdnegfEMbDqRvVnZ2dnUVZ_h_inZ2d@earthlink.com...

"Tom Biasi" <tombiasi***@optonline.net> wrote in
news:jPmdnZ6cgLpkhhvVnZ2dnUVZ_rHinZ2d@giganews.com:


"Kris Krieger" <me@dowmuff.in> wrote in message
news:Ldudnee3Sd8cixvVnZ2dnUVZ_oninZ2d@earthlink.com...

Well, this is sci.electronics.basics, so I have another basic
question

I've been looking into buying solar cells, and I see a lot of
this sort of description:

"Square polycrystalline silicon solar cell has an output of .42V
to .52V (open circuit) and a current of >1.2amp (short
circuit)."

What I'm wondering is, which one translates into how much the
cell will produce when it's all connected up in something like a
light or motor or so
on? I'd assume that'd be "closed circuit", but better to ask
and know, than to assume.

Thanks in advance!

- Kris

When you hook something up to it that's called loading it.
The specs you quote indicate the maximum the cell can supply.
If your load uses the spec voltage and draws less than the spec
current you are loading within spec of that device.

Tom


OK, that makes sense - so the maximum voltage a cell can deliver
(in perfect sunshine) is X volts at a current (flow) of Y amps per
hour.

Hmmm, so why do they specify (open circuit) and (short circuit)?
I did read these:
http://www.answers.com/topic/short-circuit
http://en.wikipedia.org/wiki/Short_circuit
but I still wonder why they can't just say "max current is Y amps"
- are they simply trying to indicate that, when they tested the
item, it was only
connected back to itself, without any intervening components that
might add
resistance, etc., that'd give the meter an incorrect reading?
((THe down- to-bare-earth version of that last question being, Can
I just ignore (open circuit) and (short circuit) <g!&gt)

Thanks again!

- Kris

Sure you can just ignore it but its the info that you need.
When they specify open circuit voltage its saying that the device
cannot deliver more than that. When you load it you will get less.
The device has internal resistance. The internal resistance effects
the maximum current that can be supplied. With a short circuit
(zero ohm load) the internal resistance is such that the device
cannot supply more current than specified. Less than a short you
can expect less voltage than open circuit and less current than
short circuit.

Tom

Oh!

OK, great, thank you! I wrote that into my Notebook

- Kris

Keep in mind that power producing devices are usually specified with
some load applied. They chose the loads we have discussed. I bet you
can find a curve describing the characteristics of your device under
different light conditions vs loads. Look and see.

Tom



I don't have a device in-hand; I'm still messing around with the
"design a high-brightness Solar Light" idea, and as I keep reading, I
keep coming up with new questions (I can find a lot of answers
via internet searches, but not all.)

I had started off wanting to use 4 ICs, based upon what I'd found at
the Maxim website; they have a lot of example application circuits,
three of which would let me do what I want, however, when I added up
all of th esub-components, it was just too expensive. So now I'm
rethinking everything.

Good! The first thing to look at is the solar cells.
How much surface area does your lantern have on which
you can install solar cells? How much power can you get
from the cells installed on that area?

A square of about 6.5" per side (apx 42 sq in).

It depends on how many I put there and how I connect them, startign with:

Your largest cost will likely be for the solar cells,

Well, they're the most expensive *single* component - I found someplace
that sells 0.5V 800mA cells for $6.95 each, and, if I use the example
power boosting circuit, it will tweak that 1V into 5V 500MA output, which
in turn would power the battery charger, so it seems sufficient (the
subtotal for the battery-charging circuit itself is about $16 or so). I
might be able to get away with 400mA, but I'm not sure. In conjunction
with the LED driver, I can use up to 6 LEDs that use up to 3.4V at about
25mA (between 20mA and 30mA seems to give the best lighting efficiency).
So those parameters are the constraints for the LEDs.

and the amount of power you can get will dictate the
limit of how much light you can produce and for how long
you can produce it.

The battery charginc example circuit will produce 1.07A if the input in 9V
- the booster puts out 5V, so I'm still trying to figure out how I'd need
to tweak the example charging circuit to figure out what components I'd
have to change for it to work properly with the lower voltage. This has
been eluding me (becasue I still just don't know enough).

100 percent of the energy your device uses will come from
the solar cells. The energy gathered cannot be increased by
clever electronic design, additional batteries, different LEDs
etc. The energy _used_ can be lowered, but the maximum energy
gathering capability is fixed by the amount of area dedicated
to solar cells.

Once you know how much power will be available from your
solar cells, you can design the rest of the electronics
based on that limitation.

The power boosting circuit is supposed to generate 5V from an input of
between 0.8V and 4.5V. The output is also supposed to be 500mA, but I
think that assumes a 3A to 4A input current, tho' that is not clear to me.

This is BTW not something I designed - I don't know nearly enough to do
that! It's on the Maxim website, Application Note 1029. I have three
example circuits from Maxim and am trying to figure out how to rig them
together, specifically, whetehr they can work together (according to the
Maxim folks, they can) and what sorts of tweaks I might have to make to get
them to be "happy".

I'm sure that an EE could look at my materials and say, "Oh, well duuuuuh!,
all you have to do is this, that, and these few other things!" But I
can't afford a design service, so here I am

For example, today I'm Googling to find out whetehr a
capacitor's "outflow" can be regulated such that it acts as a battery
(and how much it'd cost). I'm interested as a matter of curiosity in
addition to what I want to do.

For want you want to do, rechargeable batteries store and
release energy far better than capacitors.

Makes sense, but it's an interesting thought, the idea of bypassing
batteries, given both the battery-disposal issues (even rechargeables wear
out), and the combined cost of the charging circuit and the batteries
themselves. It'd just be cool if they could be bypassed

Well, at least it keeps me out of trouble !

And it can be a lot of fun.

Ed

It's just particularly challenging for me to figure this out because
physics (back when I took it in the Early Cretaceous <L!&gt was never in any
way my strong suit, but I can usually figure things out if I keep banging
my head against them long enough. I need a good book, but have no idea
which to get - what I was able to look at in the local Borders and other
shops didn't bridge the gap between the almost-absurdly basic, and the far
too complex, and I can't tell from on-line summaries whether a given book
will provide what I need. Meanwhile, I'm workign from soem textbooks that
I found in online/PDF format, which is a help. But onwards and, hopefully,
upwards

Thanks!

- Kris

 

[Kris Krieger]

ehsjr <e.h.s.j.r.removethespampunctuation@bellatlantic.net> wrote in
news:t9Iik.25$vu.21@trndny05:

Kris Krieger wrote:
[much snippage]
So now I'm
rethinking everything.

Good! The first thing to look at is the solar cells.
How much surface area does your lantern have on which
you can install solar cells? How much power can you get
from the cells installed on that area?


A square of about 6.5" per side (apx 42 sq in).

It depends on how many I put there and how I connect them[...]

Your largest cost will likely be for the solar cells,


Well, they're the most expensive *single* component - I found
someplace that sells 0.5V 800mA cells for $6.95 each, and, if I use
the example power boosting circuit, it will tweak that 1V into 5V
500MA output, which in turn would power the battery charger, so it
seems sufficient (the subtotal for the battery-charging circuit
itself is about $16 or so). I might be able to get away with 400mA,
but I'm not sure.

Ok. You can convert the voltage and current numbers to a single
power number (watts) by multiplying volts times amps. Power in
can never be less than power out - you can test your initial
design against that watt figure without ever buying a part.

DOH! OK, so that means, to get that 5V at 500mA Out, if I have 1V in, it
has to be at 2.5A (2500mA)?

In this case, you have 2 cells putting out a max of 800 mA at
.5 volts each. Each cell produces a maximum of .4 watts. (Amps
times volts = watts; .800*.5 = .4) So you have a total of .8
watts with two cells.

It is _impossible_ to tweak that into 5V 500mA with a boosting
circuit. 5V at 500mA is 2.5 watts, and you have only .8 watts
to start with. The "power" boosting circuit does not actually
boost _power_, it boosts voltage. The output power can not
exceed the input power (the power you can get from your solar
cells). That's a law of nature. No electrical circuit can
overcome that.

To get 2.5 watts output, you must have at least 2.5 watts
input. (Actually, you need a little more, because of losses
in the system.) So, you need a minimum of 7 of those cells
to get 2.5 watts, at .4 watts per cell. Putting 7 in
series would give you a maximum of 3.5 volts at .8 amps,
which equals 2.8 watts. Bear in mind that 3.5 volts at .8
amps is the maximum when the solar cells receive full sunlight.
It will be lower when they get less than noonday sun.

How many of those cells can you fit on your 42 sq in ?
That will tell you the maximum wattage you have to work
with.

OK, I think I *finally* get it!

Wow, talk about overcoming a density gradient <**DOH!** >
Sorry 'bout that.

OK, so, W (for the given circuit) is 2.5 and W=IV, so I=W/V Ok then, so,
to get those 5V going out at 500mA, using this specific voltage-boosting
circuit, what I'd need (to get that output) is at the very least one of the
following combinations:

0.5V at 5A
or
1V at 2.5A
or
2V at 1.25A
or
4V at 625mA
or
some other combination where V is between 0.8 and 4.5, and a current I such
that the resulting W (power) will be at least equal to the output power of
2.5W...

In conjunction
with the LED driver, I can use up to 6 LEDs that use up to 3.4V at
about 25mA (between 20mA and 30mA seems to give the best lighting
efficiency). So those parameters are the constraints for the LEDs.


Ok. This parameter is something you can change around, if
necessary. Using 6 25 mA 3.4V LEDs, you consume .51 watts
(.025 * 3.4 * 6). You can lower the consumption (and the
brightness) by using fewer LEDs, by running them at lower
current and by pulsing them on and off. You can also lower
the total power used over time by reducing the total amount
of on time. Conversely, you can raise the consumption by
doing the opposite. The point being, you are not limited by
physical space here, as you are when considering the solar
cells.

I'd read about the pulsing, which sounded like a great idea, but I haven't
yet figured it out.

I know I want the LEDs to run for 8 hours. So then, what I

and the amount of power you can get will dictate the
limit of how much light you can produce and for how long
you can produce it.


The battery charginc example circuit will produce 1.07A if the input
in 9V

Ok - but you need to check the watts again. 1.07 amps at 9 volts
is 9.53 watts. To produce that much wattage, you would need
to increase the number of solar cells. If you figure the maximum
number of cells you can install on your 42 sq inches, you will
know right away if that charger is feasible at first glance.


- the booster puts out 5V, so I'm still trying to figure out how I'd
need to tweak the example charging circuit to figure out what
components I'd have to change for it to work properly with the lower
voltage. This has been eluding me (becasue I still just don't know
enough).

Well, if you look at the "garden" lights (I know you have) available,
it's been eluding everyone else, too. :-(

The thing that possibly saves you is that you can charge more $ for
your product than those cheap garden lights. The thing the limits
you is the amount of electrical power you can get from solar cells.

Right on both counts

I am just convinced that eventually, I'll work somethign out, and I think
it could expand both the field of glass-work (I also have soem ideas for
using what's called "warm glass", where you melt different colors, shapes,
etc. of glass together and then use heat again to shape that) and the whole
idea of solar lighting.

Then there is a new invention:
http://news.cnet.com/8301-11128_3-9988923-54.html?hhTest=1
http://web.mit.edu/newsoffice/2008/solarcells-0710.html
whereby windows can be made to fiunction as both windows AND solar
collectors. SO I can envision combining this invention with methods used
to make glas shurricane/impast reistant, to create self-powering 'light
tubes" and other forms fo public art that can also function as self-
powering night-time lighting.

Of course, what I need to do is, as always!, rein in my over-active (and,
yeah, sometimes grandiose) imagination, and succeed with the more modest
practicalities <LOL!>


But that's what's behind this - it's more than just wanting to make "a
path/garden light", and sell a few. What I *hope* to do, beyond that, is
make something that will eventually inspire more capable (or at least
better-funded <G!&gt people to take some of those grander ideas, and bring
them to life.

100 percent of the energy your device uses will come from
the solar cells. The energy gathered cannot be increased by
clever electronic design, additional batteries, different LEDs
etc. The energy _used_ can be lowered, but the maximum energy
gathering capability is fixed by the amount of area dedicated
to solar cells.

Once you know how much power will be available from your
solar cells, you can design the rest of the electronics
based on that limitation.


The power boosting circuit is supposed to generate 5V from an input
of between 0.8V and 4.5V. The output is also supposed to be 500mA,
but I think that assumes a 3A to 4A input current, tho' that is not
clear to me.

The circuit can take an input voltage range of .8 volts up
to 6 volts. If the solar cells could provide 3 amps at .8V,
that would be 2.4 watts. You would need something over 3 amps
at .8V to get 2.5 watts output (5V*.5A). If the input from the
solar cells was 4.5 volts, then you would need only about .56
amps input to be able to get 2.5 watts output. The assumption
is a minimum input of at least .8 volts, and a minimum input
_power_ of over 2.5 watts.

By golly I think I got it now - that part at least!

Thanks for your patience...


[ ... ]

Makes sense, but it's an interesting thought, the idea of bypassing
batteries, given both the battery-disposal issues (even rechargeables
wear out), and the combined cost of the charging circuit and the
batteries themselves. It'd just be cool if they could be bypassed

Yes! Millions, maybe billions, are spent on research to make
smaller/lighter/better/more powerful energy storage devices
and if/when capacitors can be effective in doing that it will
be great. For some applications, caps work well at this today.

I like the idea of it. Fill it up, release it slowly, like a battery but
more elegant in an odd way. Batteries ae useful, but unsatisfying in a way
- they can corrode, they eventually die (even rechargeables), they're
bulky. I prefer the way that the idea of controlled-release of a
capacitor "feels" in my brain - it's a vaguely aesthetic thing

Well, at least it keeps me out of trouble !

And it can be a lot of fun.

Ed



It's just particularly challenging for me to figure this out because
physics (back when I took it in the Early Cretaceous <L!&gt was never
in any way my strong suit, but I can usually figure things out if I
keep banging my head against them long enough. I need a good book,
but have no idea which to get - what I was able to look at in the
local Borders and other shops didn't bridge the gap between the
almost-absurdly basic, and the far too complex, and I can't tell from
on-line summaries whether a given book will provide what I need.
Meanwhile, I'm workign from soem textbooks that I found in online/PDF
format, which is a help. But onwards and, hopefully, upwards


But you have artistic talent - something many of us
can only dream about.

Ed

Well, creativity takes many forms. Creativity, and dare I say it?, beauty,
are in no way limited to the arts. I can't do math (beyond some basic
geometry) to save my life, but I've had the pleasure of twice seeing
complex calculations being done by people who could simultaneously explain
what they were doing, and IMO, it was as beautiful as any symphony. I
can't write a symphony, either, just compose small bits. I've seen, and
read about, beautiful experements in biochemistry, physics, and so on, even
tho' I also can't do those myself. I'd of courase *like* to be able to do
those things, but 'doing' isn't always the point I think that
science/tech people typically don't give themselves enough credit for
creativity and the appreciation of beauty, because what one hears the most
are things said by people who are not, so to speak, "whole-brained", i.e.
they're either very left-brained, or very right-brained, and tend to miss
the proverbial Big Picture. Also, most people don't understand things that
are esoterically intellectual; that doesn't mean, however, that those
things can't be beautiful, or creative acts. Beauty, and for that matter
rationality, aren't "owned" by any one type of person, they are part of
what makes one Human - it's just that the Human capacity for both is
*expressed* differently by different types of people, and it's that
*communication gap* which is erroneously seen as a boundary. But that
boundary is maya, illusion.

What it is, is like this:
Imagine a mountain range, wherein there are two deep, beautiful lakes
teeming with fish and plant life and so on, and there is a mountain range
between the two lakes. What most people *see* is a boundary of mountains
between the two lakes, but what they don't see, and often don't understand
(because it's never explained to them), is that the lakes are actually just
two places where the level of one large aquifer is higher than the land,
and appears as lakes. One lake is science, logic, the other lake is art,
emotional expression. The aquifer is Human creativity: the capacity to
see beauty, the search for meaning.

So, the physicist speaks of stars emitting light spectra that vibrate their
way through space, and the poet spoeaks of the songs of stars. In a basic
way, both are right, both are participating in the Human search for order
and meaning, for that which connects us to the rest of the universe. The
main difference is that science is more esoteric, harder for the average
person to understand, whereas artistic expression is more direct,
immediate, more elemental in a sense, and therefore more *accessible* to
most people. But never mistake that lack of understanding, or that
difference in expression, as some sort of truth regarding the supposed
absence of creativity/beauty in science.


OK, I'll get off my sopabox now and go back to my notebooks <LOL!>

Thanks again,

- Kris

 

[Kris Krieger]

ehsjr <e.h.s.j.r.removethespampunctuation@bellatlantic.net> wrote in
news:Sa4jk.26$vu.10@trndny05:

Kris Krieger wrote:
ehsjr <e.h.s.j.r.removethespampunctuation@bellatlantic.net> wrote in
news:t9Iik.25$vu.21@trndny05:


Kris Krieger wrote:

[much snippage]

[...] I might be able to get away with 400mA,
but I'm not sure.

Ok. You can convert the voltage and current numbers to a single
power number (watts) by multiplying volts times amps. Power in
can never be less than power out - you can test your initial
design against that watt figure without ever buying a part.


DOH! OK, so that means, to get that 5V at 500mA Out, if I have 1V
in, it has to be at 2.5A (2500mA)?

Exactly (mathematically). In fact, you need a little more input
power than output power, because there is no such thing as a
perfect lossless circuit. The circuit that converts the 1
volt input to the 5 volt outlet will waste some of the power
as heat, so you might need 2.7 watts input to get 2.5 watts
output.

Ah-ha...

[snip]

OK, so, W (for the given circuit) is 2.5 and W=IV, so I=W/V Ok
then, so, to get those 5V going out at 500mA, using this specific
voltage-boosting circuit, what I'd need (to get that output) is at
the very least one of the following combinations:

0.5V at 5A
or
1V at 2.5A
or
2V at 1.25A
or
4V at 625mA
or
some other combination where V is between 0.8 and 4.5, and a current
I such that the resulting W (power) will be at least equal to the
output power of 2.5W...

Yes.

WOO-HOO!!!

OK, more things are now making more sense. I'll have to go back to some of
the simpler circuits I'd downloaded and printed out, and take a re-look
with that in mind.

[...]

I'd read about the pulsing, which sounded like a great idea, but I
haven't yet figured it out.

I know I want the LEDs to run for 8 hours. So then, what I

Ok. You can convert, again, to a useful figure.
First, you want 6 3.4V LEDs to run at 25 mA - that's
.085 watts (3.4*.025) per led and .51 watts for 6.
Next, you want them to run for 8 hours - that's .51*8
or 4.08 watt-hours. That means your solar cells will
need to provide at *least* 4.08 watt-hours every day,
even if all the electronnics was perfectly lossless. In
practice, you will need a lot more than the minimum.

Oh! OK, the cells have to produce, let's say 4.5 Watts (it's a "mor
round" number), becasue that has to go into the batteries, in turn because
that's at least how much the batteries have to be ablet o provide to the
LEDs ... and the electronics designer uses the subcomponents in the circuit
to determine the Volt and Amp balance/numbers/proportion needed to be suer
that the conditions (4.5W) are met...

Now the hard work starts. You need to determine the average
power per day you can expect from your solar cells. Then
you need to consider how many days you want your lantern
to function when the batteries cannot be re-charged by the
sun due to rain/snow/whatever. You also need to figure
that seasonally - more power will be generated in the
summer than in the winter in the northern hemisphere.

To be honest, that's why I was looking at the battery-charging IC - I
figured that, if the maximum Volts and Amps of a given set of solar cells
can charge the batteries in 4 hours (IOW, under bright, clear, sunny
conditions), tehn that same system ought to allow the batteries to charge
OK if the unit receives, for example, only 5 or 6 hours of sunlight, or, if
the sunlight is degraded due to suboptimal weather. THat's about as far as
I could go with it. So the Bbattery-charging IC was supposed toprotect the
battery from over-charging if the unit received more than 4 hours of
sunlight.

I don't know if I'm describing that in a way that makes sense. But the
math of it is too daunting for me (and I don't have any test equipment, so
I'd have to buy some to test a cell under all weather conditions - so I'm
admittedly "winging it" with the charging time).

Your worst case figure (ie lowest average power over
x days) will have to be at least 20% higher than the
4.08 watt hours per day, because you need to charge
batteries at 120 percent of the amount of energy used,
due to losses while charging. And, if there is a voltage
converter circuit used as in the ap note, there is loss
in that, too.

Oh!, I didn't know about that 120% - I'd read several battery information
pages, but I can't say whether they didn't mention that, or whether I just
forgot due to Information Overload. Well, it's now in my Notebook, at
least.

((This si something of a mini-education in the difficulties associated with
alternative energy...))


[...]

- the booster puts out 5V, so I'm still trying to figure out how I'd
need to tweak the example charging circuit to figure out what
components I'd have to change for it to work properly with the lower
voltage. This has been eluding me (becasue I still just don't know
enough).

Well, if you look at the "garden" lights (I know you have) available,
it's been eluding everyone else, too. :-(

The thing that possibly saves you is that you can charge more $ for
your product than those cheap garden lights. The thing the limits
you is the amount of electrical power you can get from solar cells.


Right on both counts

I am just convinced that eventually, I'll work somethign out,

From what I have seen of your interest and effort, I agree.
You're not like some who ask a question and disappear - you
dig your teeth in and work hard on this. Most commendable!

Well, people who know me woudl probably say "maddening" Seriously,
tho', I typically "leap before looking" and have to guard against
frustrating myself (since frustration makes me cranky). But I am
particularly (or perhaps peculiarly ) motivated to put my best effort
into doing this, becasue of the broader implications/ideas that I see
associated with it.

and I think
it could expand both the field of glass-work (I also have soem ideas
for using what's called "warm glass", where you melt different
colors, shapes, etc. of glass together and then use heat again to
shape that) and the whole idea of solar lighting.

Then there is a new invention:
http://news.cnet.com/8301-11128_3-9988923-54.html?hhTest=1
http://web.mit.edu/newsoffice/2008/solarcells-0710.html
whereby windows can be made to fiunction as both windows AND solar
collectors. SO I can envision combining this invention with methods
used to make glas shurricane/impast reistant, to create self-powering
'light tubes" and other forms fo public art that can also function as
self- powering night-time lighting.

Nice links & I like your ideas.

Thanks :0 I actually sent the "light column" idea to the fellow listed as
the lead researcher of the solar-collecting window project - I'm sure I'll
never get around to any sort of patent, so might as well at least pass
along the idea.

Of course, what I need to do is, as always!, rein in my over-active
(and, yeah, sometimes grandiose) imagination, and succeed with the
more modest practicalities <LOL!

Groan - I know exactly what you mean.

Heh, yeah, the imagination can certainly run way out ahead; it can be
difficult to self-check and be sure it remains rooted in reality. OTOH,
progress is made by pushing the envelope, so it's also good to not get
*too* rooted

As to the practical - I have an alternative for you to
consider, but it may be based on an incorrect assumption
on my part. My assumption is that you want your lanterns
to illuminate something other than themselves.

Yup.

My idea
is to use LEDs to draw attention to the lanterns, but
not use them to illuminate things. The electronic difference
is 2 mA LEDs at 2 volts vs 25 mA leds at 3.4 volts. And that
idea designed itself. By that I mean it selected a particular
solar cell (6"x6", 10V at .15 mA) that can charge 4 NiCd
1500 mA hour batteries directly through a diode. No expensive
or complicated electronics to charge the batteries, and a very
easy energy budget - .004 watts per LED vs .085 per LED.

The penalty is a change to your basic idea, if my assumption
is right. It's bright, pinpoints of red light versus much
broader white light as I think you have in mind.

Well, I have certainly been thinking, over the past 3 or 4 days, that the
"six LED" idea is probably overkill. I am stuck on the white, or at least
warm white, tho', not only for lighting reasons, but becasue it's the most
popular color, also it won't clash when I move from clear textured glass,
to colored glass.

The lower-power red LED ( "capacitor rather than batteries" OR "capacitor
in place of batteries" OR "capacitor instead of batteries")ecially in terms
of the energy-budget, is reasonable, but colors are dicey in terms of
selling.

The point here is not to push my idea, but to indicate that
there are practical alternatives the will work, even if it
turns out that your energy budget won't support what you want.
Those alternatives "penalize" what you have in mind in order
to reduce the expenditure of energy so that your energy budget
can support a different version of what you have in mind.

All that is true. I've been thniking about things like (1) LED
light/viewing angle, and (2) if the units are to be primarily decorative,
maybe it'd be better to do something separate, or at least, larger, for
brighter lighting. Larger, of course, means a more robust structure.

Take pulsing as an example. Suppose you turn your 6 LEDs on
and off 100 times each second, such that they are on for
a total time of 1/2 second and off a total time of 1/2 second,
every second. In 8 hours, they would be on for 4 hours, and off
for 4 hours, but they would appear to be on for the entire
8 hours. They produce 1/2 the light when pulsed that way,
at 1/2 the energy cost.

I think that th epulsing is definitely a great idea; I read a bit tat
mentioned even faster blinking. I just haven't yet read enough about it to
have any idea how to do it. I know there is an IC that flashes (a "555"?),
but I'd glossed over it becasue, at teh time, I didn't think "flashing so
rapidly that it look like a constant-on", Iwas thinking slower, noticeable
flashing. Live and learn, tho!

Your point is a good one - 1/2 the energy cost owuld be excellent. I just
have to go back and go over the references about flashing.

Re: light "boosting", I took apart an LED night-light, and there was a
curved plastic cone in it, painted with a highly reflective paint, that
focused the light, making more of it useable. So I got the idea of getting
an inexpensive mirror and cutting it so as to make a "mirror pyramid" - so,
rather than the light just pointing downwards, the mirrors woudl refelct it
back up an dangle it (the light) out the sides - that oughtto make it
appear brighter than the LEDs actually are, since mroe of the light will be
"useable" so to speak.

Of course, whether these or any other modification to the
original design are needed depends upon how much energy
you can get from the solar cells.

I'm convnced that I actually have to start from the beginning, firstly
becuase I was stuck on a track that I don't think was goign anywhere (woudl
require more power input than would be practical/affordable), and
secondly, because the more i learna nd understand, teh more I realize taht
I can't simply "stick stuff together", that integrating all of these things
requires a lot more planning (and, sadly for me, math )

But that's what's behind this - it's more than just wanting to make
"a path/garden light", and sell a few. What I *hope* to do, beyond
that, is make something that will eventually inspire more capable (or
at least better-funded <G!&gt people to take some of those grander
ideas, and bring them to life.


Well, this is where I see your idea having promise. Those
garden lights are feeble, and leave you hungry for something
better. You're not going to make a garden light functional
replacement. The current garden lights are supposed to
provide "accent lighting" (e.g. dimly illuminate a path)
and not look terribly ugly while doing it. Well, they succeed
in being dim, and they also "succeed" in looking at least a
little bit ugly.

<LOL!> How true. A few recent designs are interesting, but most are
underwhelming.

Your idea provides something that you want
to look at. Day or night, it will be beautiful.

THat's what I'm hoping. First one is a rectangular shape, but the design
uses clear textured glass similarly to how pen'n'ink is used, where
different combinations of lines, or dots, or otehr shapes, fill in the
design outline. I'm starting with simple shapes - one design is 5 arching
grass blades, the other is three vaguely daisy-like flowers (the market, ya
know?), panels are 10" tall and 8" wide (anything smaller would get dicey
because the leading would cover a higher proportion of the glass).

What I was originally thinking was actually making the top (with all the
lighting components) removeable so that it could also be alernately used as
a candle-holder (not as tricky as it sounds, actually).

Lighting it
at night is key to letting people see it. So, overall if it
is technically and economically feasible, I think it's a
winner.

I'm happy I'm not the only person who thinks so <L!>

I do think the technical aspect can work, but I do have to go back and re-
think the lighting, at least in terms of what type of unit design would be
best suited to what level of lighting.

I really like the idea of a "solar table lamp", for example. But that's a
different beast from a small decorative lantern.

I'm also trying to consider safety. The prototype has the textured side of
the glass inside, to keep dirt from accumulating in it, and I'm looking
into a type of clear film that's applied to house windows to make them
highly shatter-resistent. Also, the prototype will have the solar cell in
the top, so I got some aquarium sealant, and am also decifing whether to go
with encapsulated cells, or "naked" cells aht will be attached to the
underside of a clear glass panel.

The planning is certainly giving me more appreciation for people who do
this sort of thing for a living!

[snipped]

OK, I'll get off my sopabox now and go back to my notebooks <LOL!


Damn! I was enjoying the soapbox!

Ed

Which means I stepped down at a good time - *before* it got boring <LOL!>

Oh yeah, I've been googling things like "capacitors instead of batteries"
and variations fo that, and there is actually some info. SO I'm going to
look into it and see what I can see. It'd be *very* cool if I coudl skip
the batteries. Not at all sure I can figure it out, but it would
definitely be cool

Back to work now!

- Kris

 

[Tim Wescott]

Kris Krieger wrote:

Well, this is sci.electronics.basics, so I have another basic question

I've been looking into buying solar cells, and I see a lot of this sort of
description:

"Square polycrystalline silicon solar cell has an output of .42V to .52V
(open circuit) and a current of >1.2amp (short circuit)."

What I'm wondering is, which one translates into how much the cell will
produce when it's all connected up in something like a light or motor or so
on? I'd assume that'd be "closed circuit", but better to ask and know,
than to assume.

Thanks in advance!

How much the cell will produce when it's all connected up depends on

your circuit and the amount of light shining on the cell.

They give you the two points you need to characterize the cell, and
expect you to work out a good compromise between optimum power and
circuit complexity.

Note that both of their points are zero-power points: .52V * 0A = 0W,
1.2A * 0V = 0W. The highest power point is somewhere in between (_not_
at 1/2 voltage, alas, because a diode doesn't look like a linear
resistance), and the current (and possibly voltage, I dunno) at which
this 'best point' will occur varies with lighting.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

 

[ehsjr]

Kris Krieger wrote:

"Tom Biasi" <tombiasi***@optonline.net> wrote in
news:TqCdnSEHksrg4BvVnZ2dnUVZ_umdnZ2d@giganews.com:


"Kris Krieger" <me@dowmuff.in> wrote in message
news:0-6dnRnPkPIH2BvVnZ2dnUVZ_szinZ2d@earthlink.com...

"Tom Biasi" <tombiasi***@optonline.net> wrote in
news:dbGdnUzuRbk9qhvVnZ2dnUVZ_hzinZ2d@giganews.com:


"Kris Krieger" <me@dowmuff.in> wrote in message
news:c4KdnegfEMbDqRvVnZ2dnUVZ_h_inZ2d@earthlink.com...

"Tom Biasi" <tombiasi***@optonline.net> wrote in
news:jPmdnZ6cgLpkhhvVnZ2dnUVZ_rHinZ2d@giganews.com:


"Kris Krieger" <me@dowmuff.in> wrote in message
news:Ldudnee3Sd8cixvVnZ2dnUVZ_oninZ2d@earthlink.com...

Well, this is sci.electronics.basics, so I have another basic
question

I've been looking into buying solar cells, and I see a lot of
this sort of description:

"Square polycrystalline silicon solar cell has an output of .42V
to .52V (open circuit) and a current of >1.2amp (short circuit)."

What I'm wondering is, which one translates into how much the
cell will produce when it's all connected up in something like a
light or motor or so
on? I'd assume that'd be "closed circuit", but better to ask and
know, than to assume.

Thanks in advance!

- Kris

When you hook something up to it that's called loading it.
The specs you quote indicate the maximum the cell can supply.
If your load uses the spec voltage and draws less than the spec
current you are loading within spec of that device.

Tom


OK, that makes sense - so the maximum voltage a cell can deliver
(in perfect sunshine) is X volts at a current (flow) of Y amps per
hour.

Hmmm, so why do they specify (open circuit) and (short circuit)? I
did read these:
http://www.answers.com/topic/short-circuit
http://en.wikipedia.org/wiki/Short_circuit
but I still wonder why they can't just say "max current is Y amps"
- are they simply trying to indicate that, when they tested the
item, it was only
connected back to itself, without any intervening components that
might add
resistance, etc., that'd give the meter an incorrect reading?
((THe down- to-bare-earth version of that last question being, Can
I just ignore (open circuit) and (short circuit) <g!&gt)

Thanks again!

- Kris

Sure you can just ignore it but its the info that you need.
When they specify open circuit voltage its saying that the device
cannot deliver more than that. When you load it you will get less.
The device has internal resistance. The internal resistance effects
the maximum current that can be supplied. With a short circuit (zero
ohm load) the internal resistance is such that the device cannot
supply more current than specified. Less than a short you can expect
less voltage than open circuit and less current than short circuit.

Tom

Oh!

OK, great, thank you! I wrote that into my Notebook

- Kris

Keep in mind that power producing devices are usually specified with
some load applied. They chose the loads we have discussed. I bet you
can find a curve describing the characteristics of your device under
different light conditions vs loads. Look and see.

Tom



I don't have a device in-hand; I'm still messing around with the "design
a high-brightness Solar Light" idea, and as I keep reading, I keep coming
up with new questions (I can find a lot of answers via internet
searches, but not all.)

I had started off wanting to use 4 ICs, based upon what I'd found at the
Maxim website; they have a lot of example application circuits, three of
which would let me do what I want, however, when I added up all of th
esub-components, it was just too expensive. So now I'm rethinking
everything.

Good! The first thing to look at is the solar cells.
How much surface area does your lantern have on which
you can install solar cells? How much power can you get
from the cells installed on that area?

Your largest cost will likely be for the solar cells,
and the amount of power you can get will dictate the
limit of how much light you can produce and for how long
you can produce it.

100 percent of the energy your device uses will come from
the solar cells. The energy gathered cannot be increased by
clever electronic design, additional batteries, different LEDs
etc. The energy _used_ can be lowered, but the maximum energy
gathering capability is fixed by the amount of area dedicated
to solar cells.

Once you know how much power will be available from your
solar cells, you can design the rest of the electronics
based on that limitation.

For example, today I'm Googling to find out whetehr a
capacitor's "outflow" can be regulated such that it acts as a battery
(and how much it'd cost). I'm interested as a matter of curiosity in
addition to what I want to do.

For want you want to do, rechargeable batteries store and
release energy far better than capacitors.

Well, at least it keeps me out of trouble !

And it can be a lot of fun.

Ed

Thanks again,

- Kris

 

[Peter Bennett]

On Fri, 25 Jul 2008 04:39:47 GMT, ehsjr
<e.h.s.j.r.removethespampunctuation@bellatlantic.net> wrote:

Kris Krieger wrote:

I don't have a device in-hand; I'm still messing around with the "design
a high-brightness Solar Light" idea, and as I keep reading, I keep coming
up with new questions (I can find a lot of answers via internet
searches, but not all.)

I had started off wanting to use 4 ICs, based upon what I'd found at the
Maxim website; they have a lot of example application circuits, three of
which would let me do what I want, however, when I added up all of th
esub-components, it was just too expensive. So now I'm rethinking
everything.

Good! The first thing to look at is the solar cells.
How much surface area does your lantern have on which
you can install solar cells? How much power can you get
from the cells installed on that area?

I think I'd start at the light end of the project - determine how
many, and what sort of LEDs will produce adequate light for the
project - for these experiments, you can use any handy power supply.
Determine the power requirements for the selected LEDs, then see what
combination of solar panels will produce that power, and if they will
fit on the object.

If the resulting solar array will cover too much area, or cost too
much, then you will have to reduce the brightness of the LEDs, or
reduce the run time.


--
Peter Bennett, VE7CEI
peterbb4 (at) interchange.ubc.ca
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca

 

[ehsjr]

Kris Krieger wrote:

ehsjr <e.h.s.j.r.removethespampunctuation@bellatlantic.net> wrote in
news:nOcik.20$vu.8@trndny05:


Kris Krieger wrote:

"Tom Biasi" <tombiasi***@optonline.net> wrote in
news:TqCdnSEHksrg4BvVnZ2dnUVZ_umdnZ2d@giganews.com:



"Kris Krieger" <me@dowmuff.in> wrote in message
news:0-6dnRnPkPIH2BvVnZ2dnUVZ_szinZ2d@earthlink.com...


"Tom Biasi" <tombiasi***@optonline.net> wrote in
news:dbGdnUzuRbk9qhvVnZ2dnUVZ_hzinZ2d@giganews.com:



"Kris Krieger" <me@dowmuff.in> wrote in message
news:c4KdnegfEMbDqRvVnZ2dnUVZ_h_inZ2d@earthlink.com...


"Tom Biasi" <tombiasi***@optonline.net> wrote in
news:jPmdnZ6cgLpkhhvVnZ2dnUVZ_rHinZ2d@giganews.com:



"Kris Krieger" <me@dowmuff.in> wrote in message
news:Ldudnee3Sd8cixvVnZ2dnUVZ_oninZ2d@earthlink.com...


Well, this is sci.electronics.basics, so I have another basic
question

I've been looking into buying solar cells, and I see a lot of
this sort of description:

"Square polycrystalline silicon solar cell has an output of .42V
to .52V (open circuit) and a current of >1.2amp (short
circuit)."

What I'm wondering is, which one translates into how much the
cell will produce when it's all connected up in something like a
light or motor or so
on? I'd assume that'd be "closed circuit", but better to ask
and know, than to assume.

Thanks in advance!

- Kris

When you hook something up to it that's called loading it.
The specs you quote indicate the maximum the cell can supply.
If your load uses the spec voltage and draws less than the spec
current you are loading within spec of that device.

Tom


OK, that makes sense - so the maximum voltage a cell can deliver
(in perfect sunshine) is X volts at a current (flow) of Y amps per
hour.

Hmmm, so why do they specify (open circuit) and (short circuit)?
I did read these:
http://www.answers.com/topic/short-circuit
http://en.wikipedia.org/wiki/Short_circuit
but I still wonder why they can't just say "max current is Y amps"
- are they simply trying to indicate that, when they tested the
item, it was only
connected back to itself, without any intervening components that
might add
resistance, etc., that'd give the meter an incorrect reading?
((THe down- to-bare-earth version of that last question being, Can
I just ignore (open circuit) and (short circuit) <g!&gt)

Thanks again!

- Kris

Sure you can just ignore it but its the info that you need.
When they specify open circuit voltage its saying that the device
cannot deliver more than that. When you load it you will get less.
The device has internal resistance. The internal resistance effects
the maximum current that can be supplied. With a short circuit
(zero ohm load) the internal resistance is such that the device
cannot supply more current than specified. Less than a short you
can expect less voltage than open circuit and less current than
short circuit.

Tom

Oh!

OK, great, thank you! I wrote that into my Notebook

- Kris

Keep in mind that power producing devices are usually specified with
some load applied. They chose the loads we have discussed. I bet you
can find a curve describing the characteristics of your device under
different light conditions vs loads. Look and see.

Tom



I don't have a device in-hand; I'm still messing around with the
"design a high-brightness Solar Light" idea, and as I keep reading, I
keep coming up with new questions (I can find a lot of answers
via internet searches, but not all.)

I had started off wanting to use 4 ICs, based upon what I'd found at
the Maxim website; they have a lot of example application circuits,
three of which would let me do what I want, however, when I added up
all of th esub-components, it was just too expensive. So now I'm
rethinking everything.

Good! The first thing to look at is the solar cells.
How much surface area does your lantern have on which
you can install solar cells? How much power can you get
from the cells installed on that area?


A square of about 6.5" per side (apx 42 sq in).

It depends on how many I put there and how I connect them, startign with:


Your largest cost will likely be for the solar cells,


Well, they're the most expensive *single* component - I found someplace
that sells 0.5V 800mA cells for $6.95 each, and, if I use the example
power boosting circuit, it will tweak that 1V into 5V 500MA output, which
in turn would power the battery charger, so it seems sufficient (the
subtotal for the battery-charging circuit itself is about $16 or so). I
might be able to get away with 400mA, but I'm not sure.

Ok. You can convert the voltage and current numbers to a single
power number (watts) by multiplying volts times amps. Power in
can never be less than power out - you can test your initial
design against that watt figure without ever buying a part.

In this case, you have 2 cells putting out a max of 800 mA at
..5 volts each. Each cell produces a maximum of .4 watts. (Amps
times volts = watts; .800*.5 = .4) So you have a total of .8
watts with two cells.

It is _impossible_ to tweak that into 5V 500mA with a boosting
circuit. 5V at 500mA is 2.5 watts, and you have only .8 watts
to start with. The "power" boosting circuit does not actually
boost _power_, it boosts voltage. The output power can not
exceed the input power (the power you can get from your solar
cells). That's a law of nature. No electrical circuit can
overcome that.

To get 2.5 watts output, you must have at least 2.5 watts
input. (Actually, you need a little more, because of losses
in the system.) So, you need a minimum of 7 of those cells
to get 2.5 watts, at .4 watts per cell. Putting 7 in
series would give you a maximum of 3.5 volts at .8 amps,
which equals 2.8 watts. Bear in mind that 3.5 volts at .8
amps is the maximum when the solar cells receive full sunlight.
It will be lower when they get less than noonday sun.

How many of those cells can you fit on your 42 sq in ?
That will tell you the maximum wattage you have to work
with.

In conjunction
with the LED driver, I can use up to 6 LEDs that use up to 3.4V at about
25mA (between 20mA and 30mA seems to give the best lighting efficiency).
So those parameters are the constraints for the LEDs.

Ok. This parameter is something you can change around, if
necessary. Using 6 25 mA 3.4V LEDs, you consume .51 watts
(.025 * 3.4 * 6). You can lower the consumption (and the
brightness) by using fewer LEDs, by running them at lower
current and by pulsing them on and off. You can also lower
the total power used over time by reducing the total amount
of on time. Conversely, you can raise the consumption by
doing the opposite. The point being, you are not limited by
physical space here, as you are when considering the solar
cells.

and the amount of power you can get will dictate the
limit of how much light you can produce and for how long
you can produce it.


The battery charginc example circuit will produce 1.07A if the input in 9V

Ok - but you need to check the watts again. 1.07 amps at 9 volts
is 9.53 watts. To produce that much wattage, you would need
to increase the number of solar cells. If you figure the maximum
number of cells you can install on your 42 sq inches, you will
know right away if that charger is feasible at first glance.

- the booster puts out 5V, so I'm still trying to figure out how I'd need
to tweak the example charging circuit to figure out what components I'd
have to change for it to work properly with the lower voltage. This has
been eluding me (becasue I still just don't know enough).

Well, if you look at the "garden" lights (I know you have) available,
it's been eluding everyone else, too. :-(

The thing that possibly saves you is that you can charge more $ for
your product than those cheap garden lights. The thing the limits
you is the amount of electrical power you can get from solar cells.

100 percent of the energy your device uses will come from
the solar cells. The energy gathered cannot be increased by
clever electronic design, additional batteries, different LEDs
etc. The energy _used_ can be lowered, but the maximum energy
gathering capability is fixed by the amount of area dedicated
to solar cells.

Once you know how much power will be available from your
solar cells, you can design the rest of the electronics
based on that limitation.


The power boosting circuit is supposed to generate 5V from an input of
between 0.8V and 4.5V. The output is also supposed to be 500mA, but I
think that assumes a 3A to 4A input current, tho' that is not clear to me.

The circuit can take an input voltage range of .8 volts up
to 6 volts. If the solar cells could provide 3 amps at .8V,
that would be 2.4 watts. You would need something over 3 amps
at .8V to get 2.5 watts output (5V*.5A). If the input from the
solar cells was 4.5 volts, then you would need only about .56
amps input to be able to get 2.5 watts output. The assumption
is a minimum input of at least .8 volts, and a minimum input
_power_ of over 2.5 watts.

This is BTW not something I designed - I don't know nearly enough to do
that! It's on the Maxim website, Application Note 1029. I have three
example circuits from Maxim and am trying to figure out how to rig them
together, specifically, whetehr they can work together (according to the
Maxim folks, they can) and what sorts of tweaks I might have to make to get
them to be "happy".

I'm sure that an EE could look at my materials and say, "Oh, well duuuuuh!,
all you have to do is this, that, and these few other things!" But I
can't afford a design service, so here I am


For example, today I'm Googling to find out whetehr a
capacitor's "outflow" can be regulated such that it acts as a battery
(and how much it'd cost). I'm interested as a matter of curiosity in
addition to what I want to do.

For want you want to do, rechargeable batteries store and
release energy far better than capacitors.


Makes sense, but it's an interesting thought, the idea of bypassing
batteries, given both the battery-disposal issues (even rechargeables wear
out), and the combined cost of the charging circuit and the batteries
themselves. It'd just be cool if they could be bypassed

Yes! Millions, maybe billions, are spent on research to make
smaller/lighter/better/more powerful energy storage devices
and if/when capacitors can be effective in doing that it will
be great. For some applications, caps work well at this today.

Well, at least it keeps me out of trouble !

And it can be a lot of fun.

Ed



It's just particularly challenging for me to figure this out because
physics (back when I took it in the Early Cretaceous <L!&gt was never in any
way my strong suit, but I can usually figure things out if I keep banging
my head against them long enough. I need a good book, but have no idea
which to get - what I was able to look at in the local Borders and other
shops didn't bridge the gap between the almost-absurdly basic, and the far
too complex, and I can't tell from on-line summaries whether a given book
will provide what I need. Meanwhile, I'm workign from soem textbooks that
I found in online/PDF format, which is a help. But onwards and, hopefully,
upwards

But you have artistic talent - something many of us
can only dream about.

Ed

Thanks!

- Kris

 

[ehsjr]

Kris Krieger wrote:

ehsjr <e.h.s.j.r.removethespampunctuation@bellatlantic.net> wrote in
news:t9Iik.25$vu.21@trndny05:


Kris Krieger wrote:

[much snippage]

So now I'm
rethinking everything.

Good! The first thing to look at is the solar cells.
How much surface area does your lantern have on which
you can install solar cells? How much power can you get

from the cells installed on that area?


A square of about 6.5" per side (apx 42 sq in).

It depends on how many I put there and how I connect them[...]


Your largest cost will likely be for the solar cells,


Well, they're the most expensive *single* component - I found
someplace that sells 0.5V 800mA cells for $6.95 each, and, if I use
the example power boosting circuit, it will tweak that 1V into 5V
500MA output, which in turn would power the battery charger, so it
seems sufficient (the subtotal for the battery-charging circuit
itself is about $16 or so). I might be able to get away with 400mA,
but I'm not sure.

Ok. You can convert the voltage and current numbers to a single
power number (watts) by multiplying volts times amps. Power in
can never be less than power out - you can test your initial
design against that watt figure without ever buying a part.


DOH! OK, so that means, to get that 5V at 500mA Out, if I have 1V in, it
has to be at 2.5A (2500mA)?

Exactly (mathematically). In fact, you need a little more input
power than output power, because there is no such thing as a
perfect lossless circuit. The circuit that converts the 1
volt input to the 5 volt outlet will waste some of the power
as heat, so you might need 2.7 watts input to get 2.5 watts
output.

In this case, you have 2 cells putting out a max of 800 mA at
.5 volts each. Each cell produces a maximum of .4 watts. (Amps
times volts = watts; .800*.5 = .4) So you have a total of .8
watts with two cells.

It is _impossible_ to tweak that into 5V 500mA with a boosting
circuit. 5V at 500mA is 2.5 watts, and you have only .8 watts
to start with. The "power" boosting circuit does not actually
boost _power_, it boosts voltage. The output power can not
exceed the input power (the power you can get from your solar
cells). That's a law of nature. No electrical circuit can
overcome that.

To get 2.5 watts output, you must have at least 2.5 watts
input. (Actually, you need a little more, because of losses
in the system.) So, you need a minimum of 7 of those cells
to get 2.5 watts, at .4 watts per cell. Putting 7 in
series would give you a maximum of 3.5 volts at .8 amps,
which equals 2.8 watts. Bear in mind that 3.5 volts at .8
amps is the maximum when the solar cells receive full sunlight.
It will be lower when they get less than noonday sun.

How many of those cells can you fit on your 42 sq in ?
That will tell you the maximum wattage you have to work
with.


OK, I think I *finally* get it!

Wow, talk about overcoming a density gradient <**DOH!**
Sorry 'bout that.

OK, so, W (for the given circuit) is 2.5 and W=IV, so I=W/V Ok then, so,
to get those 5V going out at 500mA, using this specific voltage-boosting
circuit, what I'd need (to get that output) is at the very least one of the
following combinations:

0.5V at 5A
or
1V at 2.5A
or
2V at 1.25A
or
4V at 625mA
or
some other combination where V is between 0.8 and 4.5, and a current I such
that the resulting W (power) will be at least equal to the output power of
2.5W...

Yes.

In conjunction
with the LED driver, I can use up to 6 LEDs that use up to 3.4V at
about 25mA (between 20mA and 30mA seems to give the best lighting
efficiency). So those parameters are the constraints for the LEDs.


Ok. This parameter is something you can change around, if
necessary. Using 6 25 mA 3.4V LEDs, you consume .51 watts
(.025 * 3.4 * 6). You can lower the consumption (and the
brightness) by using fewer LEDs, by running them at lower
current and by pulsing them on and off. You can also lower
the total power used over time by reducing the total amount
of on time. Conversely, you can raise the consumption by
doing the opposite. The point being, you are not limited by
physical space here, as you are when considering the solar
cells.


I'd read about the pulsing, which sounded like a great idea, but I haven't
yet figured it out.

I know I want the LEDs to run for 8 hours. So then, what I

Ok. You can convert, again, to a useful figure.
First, you want 6 3.4V LEDs to run at 25 mA - that's
..085 watts (3.4*.025) per led and .51 watts for 6.
Next, you want them to run for 8 hours - that's .51*8
or 4.08 watt-hours. That means your solar cells will
need to provide at *least* 4.08 watt-hours every day,
even if all the electronnics was perfectly lossless. In
practice, you will need a lot more than the minimum.

Now the hard work starts. You need to determine the average
power per day you can expect from your solar cells. Then
you need to consider how many days you want your lantern
to function when the batteries cannot be re-charged by the
sun due to rain/snow/whatever. You also need to figure
that seasonally - more power will be generated in the
summer than in the winter in the northern hemisphere.
Your worst case figure (ie lowest average power over
x days) will have to be at least 20% higher than the
4.08 watt hours per day, because you need to charge
batteries at 120 percent of the amount of energy used,
due to losses while charging. And, if there is a voltage
converter circuit used as in the ap note, there is loss
in that, too.

and the amount of power you can get will dictate the
limit of how much light you can produce and for how long
you can produce it.


The battery charginc example circuit will produce 1.07A if the input
in 9V

Ok - but you need to check the watts again. 1.07 amps at 9 volts
is 9.53 watts. To produce that much wattage, you would need
to increase the number of solar cells. If you figure the maximum
number of cells you can install on your 42 sq inches, you will
know right away if that charger is feasible at first glance.



- the booster puts out 5V, so I'm still trying to figure out how I'd
need to tweak the example charging circuit to figure out what
components I'd have to change for it to work properly with the lower
voltage. This has been eluding me (becasue I still just don't know
enough).

Well, if you look at the "garden" lights (I know you have) available,
it's been eluding everyone else, too. :-(

The thing that possibly saves you is that you can charge more $ for
your product than those cheap garden lights. The thing the limits
you is the amount of electrical power you can get from solar cells.


Right on both counts

I am just convinced that eventually, I'll work somethign out,

From what I have seen of your interest and effort, I agree.
You're not like some who ask a question and disappear - you
dig your teeth in and work hard on this. Most commendable!

and I think
it could expand both the field of glass-work (I also have soem ideas for
using what's called "warm glass", where you melt different colors, shapes,
etc. of glass together and then use heat again to shape that) and the whole
idea of solar lighting.

Then there is a new invention:
http://news.cnet.com/8301-11128_3-9988923-54.html?hhTest=1
http://web.mit.edu/newsoffice/2008/solarcells-0710.html
whereby windows can be made to fiunction as both windows AND solar
collectors. SO I can envision combining this invention with methods used
to make glas shurricane/impast reistant, to create self-powering 'light
tubes" and other forms fo public art that can also function as self-
powering night-time lighting.

Nice links & I like your ideas.

Of course, what I need to do is, as always!, rein in my over-active (and,
yeah, sometimes grandiose) imagination, and succeed with the more modest
practicalities <LOL!

Groan - I know exactly what you mean.
As to the practical - I have an alternative for you to
consider, but it may be based on an incorrect assumption
on my part. My assumption is that you want your lanterns
to illuminate something other than themselves. My idea
is to use LEDs to draw attention to the lanterns, but
not use them to illuminate things. The electronic difference
is 2 mA LEDs at 2 volts vs 25 mA leds at 3.4 volts. And that
idea designed itself. By that I mean it selected a particular
solar cell (6"x6", 10V at .15 mA) that can charge 4 NiCd
1500 mA hour batteries directly through a diode. No expensive
or complicated electronics to charge the batteries, and a very
easy energy budget - .004 watts per LED vs .085 per LED.

The penalty is a change to your basic idea, if my assumption
is right. It's bright, pinpoints of red light versus much
broader white light as I think you have in mind.

The point here is not to push my idea, but to indicate that
there are practical alternatives the will work, even if it
turns out that your energy budget won't support what you want.
Those alternatives "penalize" what you have in mind in order
to reduce the expenditure of energy so that your energy budget
can support a different version of what you have in mind.

Take pulsing as an example. Suppose you turn your 6 LEDs on
and off 100 times each second, such that they are on for
a total time of 1/2 second and off a total time of 1/2 second,
every second. In 8 hours, they would be on for 4 hours, and off
for 4 hours, but they would appear to be on for the entire
8 hours. They produce 1/2 the light when pulsed that way,
at 1/2 the energy cost.

Of course, whether these or any other modification to the
original design are needed depends upon how much energy
you can get from the solar cells.

But that's what's behind this - it's more than just wanting to make "a
path/garden light", and sell a few. What I *hope* to do, beyond that, is
make something that will eventually inspire more capable (or at least
better-funded <G!&gt people to take some of those grander ideas, and bring
them to life.

Well, this is where I see your idea having promise. Those
garden lights are feeble, and leave you hungry for something
better. You're not going to make a garden light functional
replacement. The current garden lights are supposed to
provide "accent lighting" (e.g. dimly illuminate a path)
and not look terribly ugly while doing it. Well, they succeed
in being dim, and they also "succeed" in looking at least a
little bit ugly. Your idea provides something that you want
to look at. Day or night, it will be beautiful. Lighting it
at night is key to letting people see it. So, overall if it
is technically and economically feasible, I think it's a
winner.

100 percent of the energy your device uses will come from
the solar cells. The energy gathered cannot be increased by
clever electronic design, additional batteries, different LEDs
etc. The energy _used_ can be lowered, but the maximum energy
gathering capability is fixed by the amount of area dedicated
to solar cells.

Once you know how much power will be available from your
solar cells, you can design the rest of the electronics
based on that limitation.


The power boosting circuit is supposed to generate 5V from an input
of between 0.8V and 4.5V. The output is also supposed to be 500mA,
but I think that assumes a 3A to 4A input current, tho' that is not
clear to me.

The circuit can take an input voltage range of .8 volts up
to 6 volts. If the solar cells could provide 3 amps at .8V,
that would be 2.4 watts. You would need something over 3 amps
at .8V to get 2.5 watts output (5V*.5A). If the input from the
solar cells was 4.5 volts, then you would need only about .56
amps input to be able to get 2.5 watts output. The assumption
is a minimum input of at least .8 volts, and a minimum input
_power_ of over 2.5 watts.


By golly I think I got it now - that part at least!

Thanks for your patience...


[ ... ]



Makes sense, but it's an interesting thought, the idea of bypassing
batteries, given both the battery-disposal issues (even rechargeables
wear out), and the combined cost of the charging circuit and the
batteries themselves. It'd just be cool if they could be bypassed

Yes! Millions, maybe billions, are spent on research to make
smaller/lighter/better/more powerful energy storage devices
and if/when capacitors can be effective in doing that it will
be great. For some applications, caps work well at this today.


I like the idea of it. Fill it up, release it slowly, like a battery but
more elegant in an odd way. Batteries ae useful, but unsatisfying in a way
- they can corrode, they eventually die (even rechargeables), they're
bulky. I prefer the way that the idea of controlled-release of a
capacitor "feels" in my brain - it's a vaguely aesthetic thing


Well, at least it keeps me out of trouble !

And it can be a lot of fun.

Ed



It's just particularly challenging for me to figure this out because
physics (back when I took it in the Early Cretaceous <L!&gt was never
in any way my strong suit, but I can usually figure things out if I
keep banging my head against them long enough. I need a good book,
but have no idea which to get - what I was able to look at in the
local Borders and other shops didn't bridge the gap between the
almost-absurdly basic, and the far too complex, and I can't tell from
on-line summaries whether a given book will provide what I need.
Meanwhile, I'm workign from soem textbooks that I found in online/PDF
format, which is a help. But onwards and, hopefully, upwards


But you have artistic talent - something many of us
can only dream about.

Ed



Well, creativity takes many forms. Creativity, and dare I say it?, beauty,
are in no way limited to the arts. I can't do math (beyond some basic
geometry) to save my life, but I've had the pleasure of twice seeing
complex calculations being done by people who could simultaneously explain
what they were doing, and IMO, it was as beautiful as any symphony. I
can't write a symphony, either, just compose small bits. I've seen, and
read about, beautiful experements in biochemistry, physics, and so on, even
tho' I also can't do those myself. I'd of courase *like* to be able to do
those things, but 'doing' isn't always the point I think that
science/tech people typically don't give themselves enough credit for
creativity and the appreciation of beauty, because what one hears the most
are things said by people who are not, so to speak, "whole-brained", i.e.
they're either very left-brained, or very right-brained, and tend to miss
the proverbial Big Picture. Also, most people don't understand things that
are esoterically intellectual; that doesn't mean, however, that those
things can't be beautiful, or creative acts. Beauty, and for that matter
rationality, aren't "owned" by any one type of person, they are part of
what makes one Human - it's just that the Human capacity for both is
*expressed* differently by different types of people, and it's that
*communication gap* which is erroneously seen as a boundary. But that
boundary is maya, illusion.

What it is, is like this:
Imagine a mountain range, wherein there are two deep, beautiful lakes
teeming with fish and plant life and so on, and there is a mountain range
between the two lakes. What most people *see* is a boundary of mountains
between the two lakes, but what they don't see, and often don't understand
(because it's never explained to them), is that the lakes are actually just
two places where the level of one large aquifer is higher than the land,
and appears as lakes. One lake is science, logic, the other lake is art,
emotional expression. The aquifer is Human creativity: the capacity to
see beauty, the search for meaning.

So, the physicist speaks of stars emitting light spectra that vibrate their
way through space, and the poet spoeaks of the songs of stars. In a basic
way, both are right, both are participating in the Human search for order
and meaning, for that which connects us to the rest of the universe. The
main difference is that science is more esoteric, harder for the average
person to understand, whereas artistic expression is more direct,
immediate, more elemental in a sense, and therefore more *accessible* to
most people. But never mistake that lack of understanding, or that
difference in expression, as some sort of truth regarding the supposed
absence of creativity/beauty in science.


OK, I'll get off my sopabox now and go back to my notebooks <LOL!

Damn! I was enjoying the soapbox!

Ed

Thanks again,

- Kris