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'[EE] Re: : propellor clock as planetarium ?'
2005\09\04@234320 by Vasile Surducan

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On 9/5/05, Bob Blick <spam_OUTbblickTakeThisOuTspamsonic.net> wrote:
>
> > White or yellow to look more like stars. RGB LEDS would be cool but
> > much more costly.
>
> White LEDs are too slow to use in a propeller clock :(

Hi Stef, hi Bob.

White LEd's maybe not but laser diodes yes (assuming a planetarium has
a surface for composing the image). And there are a plenty lasers in
red colour with less than 1 euro/pcs.

cheers
Vasile

2005\09\05@131734 by Stef Mientki

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Vasile Surducan wrote:

{Quote hidden}

Hi Vasile,

>White LEd's maybe not but laser diodes yes (assuming a planetarium has
>a surface for composing the image).
>
Yes it should have.

> And there are a plenty lasers in
>red colour with less than 1 euro/pcs.
>  
>
Well the red color is not so relaistic for a planetarium,
but the use of laser diodes could certainly solve the problem of  
focussing of the beam.
So we keep that in mind.

cheers,
Stef

>cheers
>Vasile
>
>  
>

2005\09\06@004818 by Vasile Surducan

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On 9/5/05, Bob Blick <bblickspamKILLspamsonic.net> wrote:
> White LEDs are Blue LEDs with a phosphor layer. So although the
> blue part will have a rise time <1usec, the rest of it will be slow
> responding. How slow, I don't know. White LEDs tend to be quite
> blue-looking in general.

Hi Bob, maybe your rising time problems are generated by the power supply.
Remember, a blue, pink, white or violet LED have a dropout of about 3.8V...4.3V
depends by the technology. Replacing a standard red/green/yellow LED
(powered from 5V) with one one those will not be possible for a fast
response only if you increase the voltage of the power supply.

I've seen a blue pendullum clock (in fact it was a reversed pendullum)
in one spanish souvenirs shop this summer. It looks wery well for my
eyes.

cheers,
Vasile

2005\09\06@032648 by Russell McMahon

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>> White LEDs are Blue LEDs with a phosphor layer. So although the
>> blue part will have a rise time <1usec, the rest of it will be slow
>> responding.

> Hi Bob, maybe your rising time problems are generated by the power
> supply.

His point was that white LEDs work by using a phosphor to absorb
energy at (typically mainly) one wavelength and reradiate it at other
wavelengths . The time it takes the phosphor to absorb input energy
and for the resultant emission to stabilise at a steady state is much
longer than the actual LED rise time. Similarly, when the LED is
turned off, the phosphor continues to emit light at a decreasing level
over a substantial period of time. I imagine the output decays
exponentially, so that there will be some output present for a
substantial period compared to the time taken for the output to reduce
by say 3 dB.

Overall this "soggy" and slow on, and (probably) slower off
characteristic makes LEDs that use phosphors less suited to high speed
information transfer. Phosphor response times would play a big part in
how fast you can usefully modulate them.


       RM

2005\09\07@071704 by Vasile Surducan

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On 9/6/05, Russell McMahon <.....apptechKILLspamspam.....paradise.net.nz> wrote:
> >> White LEDs are Blue LEDs with a phosphor layer. So although the
> >> blue part will have a rise time <1usec, the rest of it will be slow
> >> responding.
>
> > Hi Bob, maybe your rising time problems are generated by the power
> > supply.
>
> His point was that white LEDs work by using a phosphor to absorb
> energy at (typically mainly) one wavelength and reradiate it at other
> wavelengths . The time it takes the phosphor to absorb input energy
> and for the resultant emission to stabilise at a steady state is much
> longer than the actual LED rise time.

Russell. I'm surrounded by physicists here. Bad luck. :)
The time required by energy transfer in such a thin phosphor film is
incomparable
with the human eye accomodation (continuous perception of successive frames).
So, maybe the problem should be somewere else.

cheers,
Vasile


Similarly, when the LED is
{Quote hidden}

> -

2005\09\07@073700 by Spehro Pefhany

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At 02:17 PM 9/7/2005 +0300, you wrote:


>Russell. I'm surrounded by physicists here. Bad luck. :)
>The time required by energy transfer in such a thin phosphor film is
>incomparable
>with the human eye accomodation (continuous perception of successive frames).
>So, maybe the problem should be somewere else.
>
>cheers,
>Vasile

If the LED is moving then it will illuminate different receptors, so
a response time in the 100's of microseconds will smear the image,
despite being faster than the flicker fusion rate of the human eye by
several orders of magnitude.

However, I have at least one data point that the optical turn-off
time is claimed to have a time constant of < 0.5usec (90% decay in 1usec),
which is sufficiently fast for many such purposes (I didn't see the exact
proposed configuration for this thread, so I'm going to hedge). Say 3,000
RPM and 1 ft ~=0.3m in diameter (~1m in circumference), we have 50m/sec
surface velocity. The LED would move 0.05mm in 1usec, but 10mm in 200usec.

>Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
EraseMEspeffspam_OUTspamTakeThisOuTinterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
->> Inexpensive test equipment & parts http://search.ebay.com/_W0QQsassZspeff


2005\09\07@074950 by Wouter van Ooijen

face picon face
> Russell. I'm surrounded by physicists here. Bad luck. :)
> The time required by energy transfer in such a thin phosphor film is
> incomparable
> with the human eye accomodation (continuous perception of
> successive frames).
> So, maybe the problem should be somewere else.

Did you take into account that the LED is moving, probably rather fast?

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu
 

2005\09\07@085935 by Dave Tweed

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From: Spehro Pefhany <speffspamspam_OUTinterlog.com>
> However, I have at least one data point that the optical turn-off
> time is claimed to have a time constant of < 0.5usec (90% decay in 1usec),
> which is sufficiently fast for many such purposes (I didn't see the exact
> proposed configuration for this thread, so I'm going to hedge). Say 3,000
> RPM and 1 ft ~=0.3m in diameter (~1m in circumference), we have 50m/sec
> surface velocity. The LED would move 0.05mm in 1usec, but 10mm in 200usec.

The 18" Eyeball spins at 30 revs/sec and can put about 500 pixels around
the circumference, giving a pixel rate of 15000/sec. or 67 us/pixel. A
turn-off time on the order of 10 us would not be too slow. But it uses RGB
LEDs (no phosphors), so it wasn't even an issue for us.

I don't recall how this thread started, but if the application is for a
planetarium (projected on the inside of a dome), you'll probably want a
*lot* more pixel density than that -- at least 10x linear density, if not
100x, which begins to approach the spatial resolution of the human eye
(about 200 pixels/degree, or 6e-9 sr/pixel). This means somewhere between
10e6 and 1e9 total pixels in a half-sphere.

-- Dave Tweed

2005\09\07@141136 by Stef Mientki

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Dave Tweed wrote:

{Quote hidden}

That's exactly the idea,
although we're not sure yet to use projection, because we'll loose a lot
of brightness.

> you'll probably want a
>*lot* more pixel density than that -- at least 10x linear density, if not
>100x, which begins to approach the spatial resolution of the human eye
>(about 200 pixels/degree, or 6e-9 sr/pixel). This means somewhere between
>10e6 and 1e9 total pixels in a half-sphere.
>  
>
If you look at a star-map on a computerscreen, the stars vary (depending
on the brightness of the star) from 0.02 .. 0.5 degrees (I mean
star-degress, but don't know if that's a good english word).
Looking at a starmap on paper, the size varies from 1 .. 2 degrees.

So I think we get a quiet good image if we set our goal at 1 degree for
the brightest stars. In that case we need about 100 white LEDs over a 90
degrees  arc. To also display moon and planets, we need another 100
yellow or orange LEDs.
If we're aiming at a sphere with a diameter of 40 cm and use 3 mm LEDs,
we can't get 100 LEDs on a quarter, so we need in totally 4 rows of each
50 LEDs.

Now fortunatly stars twinkle, so we can choose a lower rotation speed,
than in normal propellor clocks, maybe even as low as 5 rev/sec.
So we have 5*360 = 2000 degrees / sec, resulting in 500 usec pulses (for
the brightest stars). Maybe this must be choosen a bit lower, to
compensate for the transmission angle of the LED.
With 500 us for the brightest stars, we can possible go downto 50 usec
for the least bright stars.

The problem is of course, that this is all paperware wisdom,
and that you can judge the result only after you've build it :-(

Writing this, and realising the 500 us for the brightest stars (I had
the feeling it was less),
I maybe could deliberatly use a stepper motor,
and turn the LEDs on/off while the motor is standing still in between
the steps ??

Stef Mientki

2005\09\07@144450 by olin piclist

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Stef Mientki wrote:
> Now fortunatly stars twinkle, so we can choose a lower rotation speed,
> than in normal propellor clocks, maybe even as low as 5 rev/sec.

That will be *very* annoying.  It's also close to the range where it will
induce epileptic ceasures in some people.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

2005\09\07@162408 by Stef Mientki

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Olin Lathrop wrote:

> Stef Mientki wrote:
>
>> Now fortunatly stars twinkle, so we can choose a lower rotation speed,
>> than in normal propellor clocks, maybe even as low as 5 rev/sec.
>
>
> That will be *very* annoying.  It's also close to the range where it will
> induce epileptic ceasures in some people.

Yes you're right.
I just did some tests with medium bright LEDs at 100 mA (goal is bright
LEDs at 200 mA),
and 5Hz is too low, 20 Hz seems to be a good compromise.
So the 1 degree equivalence is 125 usec.
Even with this "low" current and medium bright LEDs, 10us pulses (for
the weakest stars) seems to be just bright enough.

Stef


>
>
> *****************************************************************
> Embed Inc, embedded system specialists in Littleton Massachusetts
> (978) 742-9014, http://www.embedinc.com

2005\09\07@180238 by M. Adam Davis

face picon face
On 9/7/05, Stef Mientki <KILLspams.mientkiKILLspamspammailbox.kun.nl> wrote:
> Yes you're right.
> I just did some tests with medium bright LEDs at 100 mA (goal is bright
> LEDs at 200 mA),
> and 5Hz is too low, 20 Hz seems to be a good compromise.
> So the 1 degree equivalence is 125 usec.
> Even with this "low" current and medium bright LEDs, 10us pulses (for
> the weakest stars) seems to be just bright enough.

Have you considered a laser scanner assembly pointing into a fisheye
lens?  You can cover the entire dome with a few lasers, some optics,
and a fast scanner.  Would probably be less work, and perhaps cheaper,
than a spinning assembly of hundreds of LEDs.  Much less noise as
well.  Take off the translucent dome and the stars appear on the
ceiling.

-Adam

2005\09\07@184301 by Bob Blick

face picon face
> Have you considered a laser scanner assembly pointing into a fisheye
> lens?  You can cover the entire dome with a few lasers, some optics,
> and a fast scanner.  Would probably be less work, and perhaps cheaper,
> than a spinning assembly of hundreds of LEDs.  Much less noise as
> well.  Take off the translucent dome and the stars appear on the
> ceiling.

Doing a raster display with one light source wouldn't give you much
brightness. But in a fully dark room it could work. You'd also need very
fast control of the light source.

Cheers,

Bob


2005\09\07@184820 by Stef Mientki

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M. Adam Davis wrote:

{Quote hidden}

well laser projection crossed my mind,
but as my son (age 14) should do the job (and hopefully learn something
from it),
I guess laser projection is far too difficult.

> Would probably be less work, and perhaps cheaper,
>than a spinning assembly of hundreds of LEDs.  Much less noise as
>well.
>
Yes, except I doubt if it is cheaper,
I estimate that the total material costs are below Euro 100 (I'm always
an optimist ;-)
Another disadvantage (but I'm not an expert), the cheap lasers are red
or green,
and stars are white :-(

>  Take off the translucent dome and the stars appear on the
>ceiling.
>  
>
Yes that would be realy great !
triggered by you idea I just found this website:
 http://www.es.com/products/digital_theater/digistar3-laser.asp

thanks,
Stef Mientki

>-Adam
>
>  
>

2005\09\07@190449 by M. Adam Davis

face picon face
On 9/7/05, Bob Blick <spamBeGonebblickspamBeGonespamsonic.net> wrote:
> Doing a raster display with one light source wouldn't give you much
> brightness. But in a fully dark room it could work. You'd also need very
> fast control of the light source.

It doesn't have to be raster.  Laser scanners are vector devices.  Two
voice coils, one moves the X mirror, the other moves the Y mirror.

Use a laser diode (or a few with combining optics) and modulate the
beams directly.  To expirement on the cheap use a bright light source
and some optics to project a spot of light.  Although at that rate you
might as well just put a fisheye lens on a cheap projecter.  But a
laser star would be neat, if off color.

-Adam

2005\09\07@192355 by Bob Blick

face picon face
>> Doing a raster display with one light source wouldn't give you much
>> brightness. But in a fully dark room it could work. You'd also need very
>> fast control of the light source.
>
> It doesn't have to be raster.  Laser scanners are vector devices.  Two
> voice coils, one moves the X mirror, the other moves the Y mirror.

Sorry, the laser scanners I was thinking about were the types in laser
printers, they rasterize.

Cheers,

Bob


2005\09\08@000918 by Dave Tweed

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From: Stef Mientki <TakeThisOuTs.mientkiEraseMEspamspam_OUTmailbox.kun.nl>
{Quote hidden}

I was thinking about this a bit more after I sent my previous message.
My laptop has a pixel density of about 75/inch, and I sit about 18" away,
giving an optical density of about 0.042 degree/pixel, or 24 pixels/degree.

> So I think we get a quiet good image if we set our goal at 1 degree for
> the brightest stars. In that case we need about 100 white LEDs over a 90
> degrees  arc. To also display moon and planets, we need another 100
> yellow or orange LEDs.

But it isn't just a question of how big the stars are, but also how
accurately you can position them in the "sky".

And a planetarium show isn't just a big star map; the goal is to
reconstruct the actual appearance of the night sky. Excessive pixellation
will destroy that illusion very quickly.

> If we're aiming at a sphere with a diameter of 40 cm and use 3 mm LEDs,
> we can't get 100 LEDs on a quarter, so we need in totally 4 rows of each
> 50 LEDs.

Huh? You should be able to place 419 x 3mm LEDs around the circumference of
a 40 cm circle.

> Now fortunatly stars twinkle, so we can choose a lower rotation speed,
> than in normal propellor clocks, maybe even as low as 5 rev/sec.

But stars twinkle randomly, not periodically. I've seen the Eyeball running
at 15 to 20 revs/sec., and it gets really hard to maintain the illusion of
any sort of continuous image at that flicker rate.

-- Dave Tweed

2005\09\08@040648 by Alan B. Pearce

face picon face
>I just did some tests with medium bright LEDs at 100 mA (goal
>is bright LEDs at 200 mA), and 5Hz is too low, 20 Hz seems to
>be a good compromise. So the 1 degree equivalence is 125 usec.
>Even with this "low" current and medium bright LEDs, 10us
>pulses (for the weakest stars) seems to be just bright enough.

You are going to need to have a counterbalance anyway, so why not have it as
another set of leds strung along it. You will get twice the pulse rate of
the leds at a given rotation speed then, and could even make the star
twinkle by lighting only one string.

2005\09\08@141154 by Stef Mientki

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Dave Tweed wrote:

{Quote hidden}

Such a resoltion would be nice:  24 LEDs per degree.
But also due to the large beamwidth of LEDs this seems not very oppetune.

{Quote hidden}

I agree, but it depends on what your goals are, and what is practical
realizable.
Our main goals are (some are just dreams for the moment ;-)
1. show the major stars at the current location at the current time (In
Netherlands you cann't see too many stars ;-)
2. show the moon and planets (maybe even some satalites)
3. show the accelarated  movement of stars, moon and planets
4. show the effect of light polution
5. with some kind of pointer, point an area at the dome (I read
somewhere that LEDs can be used as light sensor, or the old PC-pen
trick), and the telescope outside moves to the selected area

The point I'm worried at most is a smooth accelarated movement of the
stars, thus the 1 degree resolution.

>> If we're aiming at a sphere with a diameter of 40 cm and use 3 mm
>> LEDs, we can't get 100 LEDs on a quarter, so we need in totally 4
>> rows of each 50 LEDs.
>
>
> Huh? You should be able to place 419 x 3mm LEDs around the
> circumference of
> a 40 cm circle.

If you take 1 arm of the propellor clock, it covers 90 degrees of a half
sphere.
With a diameter of 40 cm, thats radius * pi / 4 = 20*pi/2 = 30 cm.
The 3 mm LEDS have en border of 3.9 mm.
If want to drilll holes in an arc, I need some inbetween space and must
count the LEDs are not parallel,
taken up some extra space. So I estimate the central distance of he LEDs
at 5 mm.
So I can place  60 LEDS at an arc of 90 degrees.


>
>> Now fortunatly stars twinkle, so we can choose a lower rotation
>> speed, than in normal propellor clocks, maybe even as low as 5 rev/sec.
>
>
> But stars twinkle randomly, not periodically.

We've noticed that, so an improvement would probably be to add random
noise (to the on-time).

> I've seen the Eyeball running
> at 15 to 20 revs/sec., and it gets really hard to maintain the
> illusion of
> any sort of continuous image at that flicker rate.

Well maybe we should increase the speed.
I think I read somewhere that the eyeball, iball, or whatever they are
called,
runned at 30 rev / sec.
Is that correct ?

Stef Mientki

2005\09\08@144319 by olin piclist

face picon face
Stef Mientki wrote:
> I agree, but it depends on what your goals are, and what is practical
> realizable.
> Our main goals are (some are just dreams for the moment ;-)
> 1. show the major stars at the current location at the current time (In
> Netherlands you cann't see too many stars ;-)
> 2. show the moon and planets (maybe even some satalites)
> 3. show the accelarated  movement of stars, moon and planets
> 4. show the effect of light polution
> 5. with some kind of pointer, point an area at the dome (I read
> somewhere that LEDs can be used as light sensor, or the old PC-pen
> trick), and the telescope outside moves to the selected area

This sounds like a nice little project, and getting anything working at all
will give a lot of satifaction and learning.  Is there any reason you need
to project onto the inside of a hemisphere like a normal planetarium?  Why
not redefine the star machine to be viewed from outside the sphere?  That
would be a lot more achievable and novel.  After all the other way has been
done before.  You'll still have something cool to show off, perhaps even
better.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

2005\09\08@154735 by Stef Mientki

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Olin Lathrop wrote:

{Quote hidden}

Maybe I wasn't clear enough, we are going to look outside onto the half
sphere,
just like in the EyeBall. So projection is maybe the wrong word ???
But I think projecting gives a much better image, because of the
radiation pattern of the LEDs.
If you look at a narrow beamed LED, you'll see a second radiation
pattern, which is very widespread.
So the idea is to project the LEDs on the innerside of a
semi-transparant sphere and have a better picture.
I just tested it with some semi-transparent white plexiglass (Litterary
translated from Dutch we call this color "milkglass") and the effect is
disappointing.
But if you just shine the LED through a piece of (white) paper, you get
the widespread beam completely vanished, so that's what we really want.
But how do we make a (strong enough) paper sphere, or is there some
other coating which has the same effect  ??

> That
> would be a lot more achievable and novel.  After all the other way has
> been
> done before.  You'll still have something cool to show off, perhaps even
> better.

Yes, IF we get it working,
and you what the problems are (6 copyrights?  ;-)

BTW, how many LEDs did you have to control in the EyeBall ?

cheers,
Stef

2005\09\08@165032 by olin piclist

face picon face
Stef Mientki wrote:
> Maybe I wasn't clear enough, we are going to look outside onto the
> half sphere,
> just like in the EyeBall. So projection is maybe the wrong word ???
> But I think projecting gives a much better image, because of the
> radiation pattern of the LEDs.
> If you look at a narrow beamed LED, you'll see a second radiation
> pattern, which is very widespread.
> So the idea is to project the LEDs on the innerside of a
> semi-transparant sphere and have a better picture.
> I just tested it with some semi-transparent white plexiglass
> (Litterary translated from Dutch we call this color "milkglass") and
> the effect is disappointing.
> But if you just shine the LED through a piece of (white) paper, you
> get the widespread beam completely vanished, so that's what we really
> want. But how do we make a (strong enough) paper sphere, or is there
> some
> other coating which has the same effect  ??

The EyeBall works on direct viewing of the LEDs, and I think this method
makes sense.  I don't see what you gain with a diffuser.  It would fuzz the
pixels and decrease brightness.  Also the cool thing people seem to like
about the EyeBall is that the image appears to hang in space.  You don't see
the rotating arm, just the pixels.

> BTW, how many LEDs did you have to control in the EyeBall ?

The first EyeBall had 16 LEDs taking up about 3 1/2 inches on a 12 inch
diameter sphere.  It was designed to display text with a single built in
font.  The second EyeBall is 18 inches in diameter and has 96 RGB LEDs
creating a vertical display height of about a foot.  That's 188 total LEDs
that can each be modulated to 2 bits of intensity per pixel.  That is
sufficient to display recognizable individual faces, although that's mostly
a bonus.  They originally cared most about arbitrary downloadable fonts and
simple low-color logos.  They didn't complain though when we added an extra
bit per color per pixel.

The total display is 512 x 96 pixels.  There is a dsPIC handling the data
from the rendering processor (which is another dsPIC) and managing a CPLD
that clocks the data to the LEDs.  If you work it out, 512 x 96 pixels x
30Hz x 8 bits/pixel comes out to a significant data rate.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

2005\09\08@184722 by Stef Mientki

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>The EyeBall works on direct viewing of the LEDs, and I think this method
>makes sense.  I don't see what you gain with a diffuser.  It would fuzz the
>pixels and decrease brightness.
>
A piece of paper looks really nice, it indeed decreases brightness, but
the large advantage of the diffuser is that you can see the star at any
place on the sphere and I think that's different then the goal of the
EyeBall.

{Quote hidden}

Wow, that's a whole lot,
I didn't realize that it was so much bandwidth.
(And I wanted it to realize with just 1 16F877, still hoping  :-(

cheers,
Stef

2005\09\09@043155 by Alan B. Pearce

face picon face
>This sounds like a nice little project, and getting anything working
>at all will give a lot of satifaction and learning.  Is there any
>reason you need to project onto the inside of a hemisphere like a
>normal planetarium?

I understood that was what he is setting out to do all along. Essentially a
dome around the size of your eyeball device, with the stars inside, but
viewed from outside. This is also why the possibility was noted (in a post
about 3 or 4 before yours) about having the device show the current star
view, shine a laser pointer at a spot in the sky of the dome, and this
causes a telescope outside to go look at that spot in the sky so you can
look at the real constellation.

There was some discussion at one stage about then taking the dome off, and
having the leds project onto the ceiling, but I think that was essentially
thrown out.

2005\09\09@075945 by Vasile Surducan

face picon face
On 9/9/05, Stef Mientki <s.mientkiEraseMEspam.....mailbox.kun.nl> wrote:
{Quote hidden}

I think you can. There are some specialised LED drivers which are
doing most of the job. You don't need another processor. The price is
about $1/pcs and have programable intensity, etc.
Take a look here: http://www.mblock.com.tw/
Maxim have something equivalent with the low cost chips manufactured here.
Unfortunately they have poor distributors in the Europe.

cheers,
Vasile

2005\09\09@092620 by Mchipguru

picon face
It is a long way from the original design I did for them with the PIC 16 processors. Back then the cost constraints and time frames were not reasonable but I can say the project has evolved very nicely from the original concept.
Larry
{Quote hidden}

> --

2005\09\13@021315 by Jason

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From: "Vasile Surducan" <RemoveMEpiclist9TakeThisOuTspamspamgmail.com>
Sent: Friday, September 09, 2005 4:59 AM

> I think you can. There are some specialised LED drivers which are
> doing most of the job. You don't need another processor. The price is
> about $1/pcs and have programable intensity, etc.
> Take a look here: http://www.mblock.com.tw/
> Maxim have something equivalent with the low cost chips manufactured here.
> Unfortunately they have poor distributors in the Europe.

I finally had a chance to look at those chips in detail.  They seem to be
little more than shift registers.  Are there LED driver chips that will
automatically do the PWM to get variable brightness? DIP packaging is
required for me


2005\09\14@075131 by Vasile Surducan

face picon face
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On 9/13/05, Jason <EraseMEpicspamspamspamBeGonecanadaspeaks.com> wrote:
> From: "Vasile Surducan" <RemoveMEpiclist9KILLspamspamgmail.com>
> Sent: Friday, September 09, 2005 4:59 AM
> > > I think you can. There are some specialised LED drivers which are
> > doing most of the job. You don't need another processor. The price is
> > about $1/pcs and have programable intensity, etc.
> > Take a look here: http://www.mblock.com.tw/
> > Maxim have something equivalent with the low cost chips manufactured here.
> > Unfortunately they have poor distributors in the Europe.
> > I finally had a chance to look at those chips in detail.  They seem to be
> little more than shift registers.  Are there LED driver chips that will
> automatically do the PWM to get variable brightness? DIP packaging is
> required for me

They have DIP packages and fully programable brightness, matched up to
16 LED columns/lines. 25MHz maximum clock. They are nice and cheap but
difficult to get in the Europe. Maybe much easy in Canada.

See attached a very good alternative for a propeller clock.
Photo taken from a romanian tourist. Water fall clock. Japanese design. Very clever !

cheers,
Vasile


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2005\09\16@054332 by Alan B. Pearce

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>See attached a very good alternative for a propeller clock.
>Photo taken from a romanian tourist. Water fall clock.
>Japanese design.
>Very clever !

Wow, just the thing to have outside a high tech company.

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