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'[PIC]: Mechanically scanned display'
2001\12\31@095732 by Dale Botkin

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Joris van den Heuvel <spam_OUTjoris.bassTakeThisOuTspamPLANET.NL> said:

> - diameter is 1 meter across

Wow.

> I'll be putting up a web page.

I'll be visiting it for sure!!  8-)

Dale

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2001\12\31@152326 by Mark Newland

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Very impresive.  Now to implement that on the prop of an airplane and
display gauge information would be really cool

Joris van den Heuvel wrote:

{Quote hidden}

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2001\12\31@184825 by Michael Coop

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Now a bit of floating sin/cos to flatten out the images (rather than
wrapping around the z-axis !!)

Excellent product !!

I can think of a large market if you can get rid of the shaft encoder...
the display must be able to mount 'effectively' in free space, so some other
method for determining the rotation start point is needed.... minimum
clearance from nearest static object is about 4--to-6 inches - so hall
effect is not an option - perhaps an IR  pair at the index point ??

{Original Message removed}

2001\12\31@192417 by Jinx

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>   I'll be putting up a web page.

Looking forward to it

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2001\12\31@220955 by Jinx

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Are the jagged edges on the characters just a result of the photo or
do they smooth out because of persistence of vision ? You probably
took a high speed picture so the characters weren't blurred

Do you plan to centre the date about 12 o'clock ? It would look better
it was balanced

Great effort, hats off

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'[PIC]: Mechanically scanned display'
2002\01\01@050622 by Joris van den Heuvel
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I'm glad you like it!

Today, it ran 5 hours continuously at a new year's party in the venue I work
at (PARA, like the logo says). People came up to me saying how much they
liked it.

Jinx wrote:

> Are the jagged edges on the characters just a result of the photo or
> do they smooth out because of persistence of vision ? You probably
> took a high speed picture so the characters weren't blurred

The jagged edges are a result of jpeg compression and the need to turn the
brightness WAY up, because my digital camera isn't very sensitive. Each
pixel does fade out at the start and end, but the picture is as sharp as
possible and as static as the rotation speed allows.

> Do you plan to centre the date about 12 o'clock ? It would look better
> it was balanced

The date would look better if it were balanced at 12 o'clock, but then I'd
have to calculate the width of each displayed line, and that's complicated.
I retreive the character pixel patterns real time through an ASCII-like
buffer and a character ROM table, and the type face is proportional.

Micheal Coop wrote:

> I can think of a large market if you can get rid of the shaft encoder...
> the display must be able to mount 'effectively' in free space, so some
other
> method for determining the rotation start point is needed.... minimum
> clearance from nearest static object is about 4--to-6 inches - so hall
> effect is not an option - perhaps an IR  pair at the index point ??

? I'm not sure what you mean. Mount in free space? The shaft encoder is
actually an IR triplet (two for direction and position - only one used - and
one for index) generating 480 pulses per rotation and 1 index.

I like the "large market" thinking! But, as with many people, I'm a
technician, not a businessman. I have my own (spare time) business, building
professional speaker cabinets, but my book keeping s*cks, really. And I'm
completely clueless on tax forms.

As I said, I'll be putting up a page about it on my personal web site. When
I'm done (maybe today) it's at http://home.planet.nl/~heuv0283

TTYL

Joris.

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2002\01\01@052953 by Michael Coop

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? I'm not sure what you mean. Mount in free space? The shaft encoder is
actually an IR triplet (two for direction and position - only one used - and
one for index) generating 480 pulses per rotation and 1 index.

My applicaiton - we can't have any external connections other than the
physical mounting, and the 'propeller' itself won't be spinning, but rather
the object it is attached to /will/ be... hence there is no relative motion
that can be detected with the shaft encoder. The bearing and mounting of the
host is already defined and I can't possibly change those elements.


I look forward to the web page - and I too am hopeless commercially - but I
have friends !

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2002\01\01@055940 by Jinx

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> I like the "large market" thinking!

Some of my experiences that may help. I've a great interest in
chronometers, especially time-keeping kinetic sculptures and
automatons. Although they look great, it's a limited market.
People are just too conservative, trust me. You may be better
focussing on a non-retail market for such a specialised clock.
That's not to say you couldn't miniaturise it, but I think you
know that in your case bigger is better

In NZ at least, public clocks are not common. And any old ones
are almost always in the staid Palace of Westminster (Big Ben)
styling and less than 100 years old. Maori were not into clocks
at all so anything here is modern and Western. There aren't, for
example, medieval Bavarian automatons (knights on horse back
etc) found in Middle Europe. Quite frankly, NZ architecture and
urban design is awful, and I could think of very few places to put
something like that

I'd like to get some of my own creative pieces out there, but town
councils, in my experience, are reluctant to do anything that might
"upset" ratepayers. So I'm looking at other alternatives

First, corporations, especially those with a budget for design and
artworks. And particularly if they have a product than can be used
as the basis for a piece. The local head office of Ajax GKN, who
make screws, nails, bolts, etc have a huge landscape made of
them. Looks great

Second, schools or colleges. Maybe approach the art department.
Some friends of mine in the Inventors Trust use the students at a
local polytech for labour and free designs, As the students need
projects for coursework, my friends persuaded the tutors to accept
their products for the students to work on. A secondary school
might be worth a try, if you can fund it yourself or find a sponsor.
Perhaps somehow work in a theme that would appeal to students

Third, include a sponsor's logo. If you strike it lucky, they may pay
for it and find a good public location too. It advertises them and also
provides a public service, although having giant clocks too close
together would lessen the impact. How about selling one to the
company you work for ?

Fourth, shopping malls. Almost a perfect environment for an LED
clock. Conversation piece, will get stared at a lot. Include an ad
in it to sell more

You can probably come up with a few ideas of your own. I wish
you good luck, and hope you come across more people willing
to give it a go than I have

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2002\01\01@085239 by Tom Mariner

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Hello Joris,

Did a toy with the same concept except it was a 18 inch black tube with
seven LED's and an alpha keyboard on the handle. One would move it back and
forth in an arc and the letters would appear as in a moving "Times Square"
display. It was done for Ideal Toy, who got a patent on the idea and sold
into the hundreds of thousands.

It was basically a Pic 1655A (NMOS), dot LEDs, a keyboard, a metal bead, and
some "C" Cells. The problem was storing the input message in 26 bytes of
RAM -- Had to use some crazy compression.

Funny story about the product development: In order to see the weak LED's
during testing, I would have to wave the wand under the workbench to shield
the overhead fluorescent lights. One day during testing, a group was being
shown through the plant as I was "testing" the prototype. After a few
moments of silence I heard the group break into laughter. When I looked up,
I realized that they were looking at this fellow vigorously moving something
back and forth between his legs under the table! No really -- I was testing
the product.

Tom
 {Original Message removed}

2002\01\01@100843 by Bob Ammerman

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Here is an idea to solve the 'no shaft encoder' limitation:

Simple hang a weight on a bearing around the shaft. The outside race of the
bearing will be a pretty good static reference, especially if its motions
(mostly pendular I would think) are averaged out. This technique is used for
odometers that are attached to the wheels of big-rig trailers.

Bob Ammerman
RAm Systems

----- Original Message -----
From: "Tom Mariner" <RemoveMEtmarinerTakeThisOuTspamOPTONLINE.NET>
To: <spamBeGonePICLISTspamBeGonespamMITVMA.MIT.EDU>
Sent: Tuesday, January 01, 2002 5:40 AM
Subject: Re: [PIC]: Mechanically scanned display


> Hello Joris,
>
> Did a toy with the same concept except it was a 18 inch black tube with
> seven LED's and an alpha keyboard on the handle. One would move it back
and
> forth in an arc and the letters would appear as in a moving "Times Square"
> display. It was done for Ideal Toy, who got a patent on the idea and sold
> into the hundreds of thousands.
>
> It was basically a Pic 1655A (NMOS), dot LEDs, a keyboard, a metal bead,
and
> some "C" Cells. The problem was storing the input message in 26 bytes of
> RAM -- Had to use some crazy compression.
>
> Funny story about the product development: In order to see the weak LED's
> during testing, I would have to wave the wand under the workbench to
shield
> the overhead fluorescent lights. One day during testing, a group was being
> shown through the plant as I was "testing" the prototype. After a few
> moments of silence I heard the group break into laughter. When I looked
up,
> I realized that they were looking at this fellow vigorously moving
something
> back and forth between his legs under the table! No really -- I was
testing
> the product.
>
> Tom
>   {Original Message removed}

2002\01\01@175846 by Joris van den Heuvel

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It's up. http://home01.wxs.nl/~heuv0283/

If that don't work, try http://home.planet.nl/~heuv0283



{Original Message removed}

2002\01\01@181742 by Joris van den Heuvel

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:D  Hahaha, Tom, you crack me up! Must've been some sight!


Joris.


----- Original Message -----
From: Tom Mariner <TakeThisOuTtmarinerEraseMEspamspam_OUTOPTONLINE.NET>
To: <RemoveMEPICLISTspamTakeThisOuTMITVMA.MIT.EDU>
Sent: Tuesday, January 01, 2002 2:40 PM
Subject: Re: [PIC]: Mechanically scanned display


> Hello Joris,
>
> Did a toy with the same concept except it was a 18 inch black tube with
> seven LED's and an alpha keyboard on the handle. One would move it back
and
> forth in an arc and the letters would appear as in a moving "Times Square"
> display. It was done for Ideal Toy, who got a patent on the idea and sold
> into the hundreds of thousands.
>
> It was basically a Pic 1655A (NMOS), dot LEDs, a keyboard, a metal bead,
and
> some "C" Cells. The problem was storing the input message in 26 bytes of
> RAM -- Had to use some crazy compression.
>
> Funny story about the product development: In order to see the weak LED's
> during testing, I would have to wave the wand under the workbench to
shield
> the overhead fluorescent lights. One day during testing, a group was being
> shown through the plant as I was "testing" the prototype. After a few
> moments of silence I heard the group break into laughter. When I looked
up,
> I realized that they were looking at this fellow vigorously moving
something
> back and forth between his legs under the table! No really -- I was
testing
> the product.
>
> Tom
>   {Original Message removed}

2002\01\02@001213 by Brandon Fosdick

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Joris van den Heuvel wrote:
>
> It's up. http://home01.wxs.nl/~heuv0283/
>
> If that don't work, try http://home.planet.nl/~heuv0283

Nice job.

How about a holographic version? :)

Maybe if you rotate the LED bar around its long axis really really fast and put
LEDs on more than one side...

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2002\01\02@040401 by uter van ooijen & floortje hanneman

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> It's up. http://home01.wxs.nl/~heuv0283/

Nice.
BTW the link (in the text) to your employer does not 'kill' the framing. (I
followed the link looking for (freelance) work, but it is too far away for
Dutch (my?) starndards. I guess Americans would call it next door).

Wouter van Ooijen

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2002\01\02@104035 by Raymond Liu

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I am wondering how quiet this clock is? It's going to be annoying to put
such a device in a place like office if it is not quiet enough.

--Raymond

{Original Message removed}

2002\01\02@110837 by Dale Botkin

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Raymond Liu <RLiuEraseMEspam.....applanix.com> said:

> I am wondering how quiet this clock is? It's going to be annoying to put
> such a device in a place like office if it is not quiet enough.

That would depend on the construction...  if one were to use a quiet motor at
a relatively low speed and streamlined parts, it probably wouldn't be too
noisy.  If it's just a square bar spinning at 3600RPM, of course, it will be
much noisier.

I'm thinking about one for my office -- well, my cubicle.  I'm thinking about
a dual-purpose device...  if I build the clock/display using a fairly good
sized prop for an R/C airplane, I can have it serve as a fan as well to keep
air moving.  Will have to spin up a couple and see if that makes a lot of
noise.

On the other hand, in a cubicle a little white or sort-of-white noise might
not be a bad hing, I hear it cuts down on distractions from outside noises.
I get a lot of conversation and keyboard sound from adjacent cubes, maybe I
*should* build a slightly noisy clock!

Dale

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2002\01\02@111114 by Roman Black

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Jinx wrote:
{Quote hidden}

Have you considered approaching a marketing
company, one that owns local billboards etc,
and sells ad space to others. They might be
willing to cut a deal where they "hire" the
machines from you, put other peoples ads on
them with a value added service like a clock
or weather data etc.
-Roman

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2002\01\02@111640 by Tim McDonough

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> I'm thinking about one for my office -- well, my cubicle.  I'm thinking
about
> a dual-purpose device...  if I build the clock/display using a fairly good
> sized prop for an R/C airplane, I can have it serve as a fan as well to
keep
> air moving.  Will have to spin up a couple and see if that makes a lot of
> noise.

Find a large diameter, low pitch prop or you may end up moving a lot more
air than you want! For model airplane applications on electric powered
planes I feel that the APC brand props give less "prop noise" than some
others.

Tim

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2002\01\02@112931 by David VanHorn

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At 04:07 PM 1/2/02 +0000, Dale Botkin wrote:
>Raymond Liu <EraseMERLiuspamapplanix.com> said:
>
> > I am wondering how quiet this clock is? It's going to be annoying to put
> > such a device in a place like office if it is not quiet enough.
>
>That would depend on the construction...  if one were to use a quiet motor at
>a relatively low speed and streamlined parts, it probably wouldn't be too
>noisy.  If it's just a square bar spinning at 3600RPM, of course, it will be
>much noisier.

I would think in terms of a disk.  Much easier to fab, and much less
balancing concerns.

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2002\01\02@114856 by Roman Black

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Joris van den Heuvel wrote:
>
> I'm glad you like it!
>
> Today, it ran 5 hours continuously at a new year's party in the venue I work
> at (PARA, like the logo says). People came up to me saying how much they
> liked it.

> I'll be putting up a page about it on my personal web site.
> I'm done (maybe today) it's at http://home.planet.nl/~heuv0283


That's a really clever gadget you made there. :o)
-Roman

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2002\01\02@125715 by Joris van den Heuvel

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Thanks for the replies, guys.



Brandon Fosdick wrote:

> Nice job.
>
> How about a holographic version? :)
>
> Maybe if you rotate the LED bar around its long axis really really fast
and put
> LEDs on more than one side...
>

Heheh, that would have to be fast. I think I'd be more tempted to use dual
color (dare I say RGB) leds and make a color display.

Wouter van Ooijen wrote:

> Nice.
> BTW the link (in the text) to your employer does not 'kill' the framing.
(I
> followed the link looking for (freelance) work, but it is too far away for
> Dutch (my?) starndards. I guess Americans would call it next door).

I'll check my site and try to get the link to appear outside my frameset.
Any suggestions?

Raymond Liu wrote:

> I am wondering how quiet this clock is? It's going to be annoying to put
> such a device in a place like office if it is not quiet enough.

The original motor (the blue one, which is now disconnected) didn't make a
single noise, and the wings deal with most of the wind noise, but the gears
on the larger motor do tend to make an annoying fuzz. Maybe I should try and
get better gears, made of metal.

Dale Botkin wrote:

> I'm thinking about one for my office -- well, my cubicle.  I'm thinking
about
> a dual-purpose device...  if I build the clock/display using a fairly good
> sized prop for an R/C airplane, I can have it serve as a fan as well to
keep
> air moving.

When I painted the wings black (yes they're black now) they had curled up a
bit, but I didn't notice until I tested. There was this incredible wind in
my living room, and the rotor was a tad slower ;-)

David VanHorn wrote:

> I would think in terms of a disk.  Much easier to fab, and much less
> balancing concerns.

Of course I considered a disk, but I don't think the 1/8" axis and its 1/2"
ball bearings would have lasted long with the added weight. If I can find or
make a larger axis and larger ball bearings, this might be worth
considering.


Regards,
Joris.

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2002\01\02@132624 by David VanHorn

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>
>The original motor (the blue one, which is now disconnected) didn't make a
>single noise, and the wings deal with most of the wind noise, but the gears
>on the larger motor do tend to make an annoying fuzz. Maybe I should try and
>get better gears, made of metal.

Belt drive would be the quietest option.
Plastic gears, like nylon, are rather quiet.
Metal gears can be quiet, but only if very well ($$) made.

>Of course I considered a disk, but I don't think the 1/8" axis and its 1/2"
>ball bearings would have lasted long with the added weight. If I can find or
>make a larger axis and larger ball bearings, this might be worth
>considering.

1-2 pounds isn't very much, and you could always counterweight it so that
the bearing doesn't see any skewed load, just weight.  I'm sure there are
suitable bearings.  You would probably want to allow for replacement though.

For bonus points, add Wimshurst hardware, and use that to power the circuit :)

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2002\01\02@144324 by uter van ooijen & floortje hanneman

picon face
> > BTW the link (in the text) to your employer does not 'kill' the framing.
> (I
> > followed the link looking for (freelance) work, but it is too far away
for
> > Dutch (my?) starndards. I guess Americans would call it next door).
>
> I'll check my site and try to get the link to appear outside my frameset.
> Any suggestions?

add
  target=_top
to the hyperlink

Wouter van Ooijen

Van Ooijen Technische Informatica: http://www.voti.nl
Jal compiler for PIC uC's:  http://www.voti.nl/jal
PICs kopen? http://www.voti.nl/shop

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2002\01\02@160756 by Jinx

face picon face
> Have you considered approaching a marketing
> company, one that owns local billboards etc,

If someone can make money off your clock then you
might have a chance

Some other suggestions (found my notes) - you may
have to wear the construction costs for "sale or return"

Interior designers or architects, access to flash houses
or commercial clients

Techno-toy retailers, the sort that sell Newtons Cradles
and other "executive" toys. Generally quite classy

Art galleries, perhaps not a big audience, might be good
for contacts and design suggestions

Clock retailers

Offer it as a kit to electronic retailers or magazines

Trade or second-hand (they do advertise new stuff) papers

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2002\01\02@161822 by Morgan Olsson

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If we use more than one string of LEDs it need less RPM.
I.e. four 90° angular spaced strings of leds only need 1/4 rpm.
Of course they need to overlap their display content exactly.

And full color red/green/blue LEDS would be nice.  (multivilor texts and logos, different coluur of hour, minute sec pointers etc etc)

Ah, and programmable via RS232, and...

...

/Morgan

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2002\01\02@162454 by Dale Botkin

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Tim McDonough <RemoveMEtimEraseMEspamEraseMEmcdonough.net> said:

> > I'm thinking about one for my office -- well, my cubicle.  I'm thinking
> about
> > a dual-purpose device...  if I build the clock/display using a fairly good
> > sized prop for an R/C airplane, I can have it serve as a fan as well to
> keep
> > air moving.  Will have to spin up a couple and see if that makes a lot of
> > noise.
>
> Find a large diameter, low pitch prop or you may end up moving a lot more
> air than you want! For model airplane applications on electric powered
> planes I feel that the APC brand props give less "prop noise" than some
> others.

I'm thinking a nice wood Top-Flite 16/6 or 18/6, at lowish RPM.  Now I'm
wondering about the LEDs...  I see LEDs ranging from <1 to 9000mcd.  No clue
as to how bright I will need to use, anyone who has built a propeller clock
have any input on that?

Dale

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2002\01\02@163107 by Martin Baker

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Hmmmm....

I am compelled to wonder if one could modify this so that it could be used
on an automobile wheel cover to spell out appropriate commentary on other
peoples driving....

M

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2002\01\02@164604 by James Paul

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Morgan,

I don't know about the other stuff, but the RGB LED's are about
$6.00 USD per piece.  At least the ones I looked at were.  I can't remember the company name right off hand, but if you need it,
I can find it for you.


                                      Regards,

                                        Jim



{Quote hidden}

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2002\01\02@165104 by Brandon Fosdick

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Morgan Olsson wrote:
>
> If we use more than one string of LEDs it need less RPM.
> I.e. four 90° angular spaced strings of leds only need 1/4 rpm.
> Of course they need to overlap their display content exactly.
>
> And full color red/green/blue LEDS would be nice.  (multivilor texts and logos, different coluur of hour, minute sec pointers etc etc)

Or keep the RPM the same and have 3 strings, each of a different color. Or have
twice as many strings as colors and cut the RPM in half.

With multiple strings you could use multiple processors, each displaying a
version of the image rotated by the angle between the strings. It would be easy
to keep all of the uC's sync'd if they run the same code and see the same timing
pulse.

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2002\01\02@170853 by David VanHorn

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At 03:45 PM 1/2/02 +0600, James Paul wrote:
>  Morgan,
>
>  I don't know about the other stuff, but the RGB LED's are about
>  $6.00 USD per piece.  At least the ones I looked at were.
>  I can't remember the company name right off hand, but if you need it,
>  I can find it for you.

Red string, Green string, Blue string, each 120 degrees apart.
Put the display data in three bits of a port and clock it all in parallel,
so that there is no sync problem.

Implement a pendulum on the rotating display, and sell ad space on both
sides. :)

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2002\01\02@170929 by Fabio Pereira

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----- Original Message -----
From: "James Paul" <RemoveMEjamespspam_OUTspamKILLspamINTERTEX.NET>
To: <RemoveMEPICLISTTakeThisOuTspamspamMITVMA.MIT.EDU>
Sent: Wednesday, January 02, 2002 1:45 AM
Subject: Re: [PIC]: Mechanically scanned display


Morgan,

I don't know about the other stuff, but the RGB LED's are about
$6.00 USD per piece.  At least the ones I looked at were.
I can't remember the company name right off hand, but if you need it,
I can find it for you.


                                      Regards,

                                        Jim


Hey Jim:

I would like to put my hands in some of them too ;-D
Let me know if you find the Manufacturer and/or places to buy ....

TIA

Fabio Pereira

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2002\01\02@234108 by Karl Seibert

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Nichia ( http://www.nichia.com ) has them, but I haven't
checked the price recently.

Karl


Quoting Fabio Pereira <EraseMEfabiospamspamspamBeGonePP.ADV.BR>:

> {Original Message removed}

2002\01\03@031725 by Alexandre Domingos F. Souza

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> I don't know about the other stuff, but the RGB LED's are about
> $6.00 USD per piece.  At least the ones I looked at were.
> I can't remember the company name right off hand, but if you need it,
> I can find it for you.

       RGB leds? Red, Green and Blue???? :oO


---8<---Corte aqui---8<----

Alexandre Souza
RemoveMEtaitoKILLspamspamterra.com.br
http://planeta.terra.com.br/lazer/pinball/

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2002\01\03@044328 by Ward, David

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There is a british company putting LED displays onto Race Car Wheels for
advertising - I suppose it's practically the only place that's left to put
adverts on.

http://www.adflash.com



David F H Ward
Electronics Design Engineer
Sira Electro-Optics Ltd, South Hill, Chislehurst, Kent, UK, BR7 5EH
Tel: +44(0)20 8467 2636, Fax: +44(0)20 8467 6515
email: David_WardSTOPspamspamspam_OUTsiraeo.co.uk
http://www.siraeo.co.uk



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{Original Message removed}

2002\01\03@125544 by Morgan Olsson

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Hej David VanHorn. Tack för ditt meddelande 23:10 2002-01-02 enligt nedan:
>At 03:45 PM 1/2/02 +0600, James Paul wrote:
>> Morgan,
>>
>> I don't know about the other stuff, but the RGB LED's are about
>> $6.00 USD per piece.  At least the ones I looked at were.

This http://www.elfa.se/elfa/produkter/se/20/2019296.htm is a 2 USD SMD RGB LED By Everlight sold in the Nordic by http://www.elfa.se

>Red string, Green string, Blue string, each 120 degrees apart.
>Put the display data in three bits of a port and clock it all in parallel,
>so that there is no sync problem.

...Or six, nine, twelve strings for lower RPM and higher luminance...
Well, expensive, but cheaper than a fyll X/Y matrix anyway.

I would guess that color combinations (i.e. R+G to make yellow) would look very flickery at low rpm:  R, G, dark, R, G, Dark, etc...)

Just delay the data between the strings of the same color X rotation steps and there is very little extra processig power needed.

/Morgan

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2002\01\04@012615 by Roman Black

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David VanHorn wrote:
>
> >
> >The original motor (the blue one, which is now disconnected) didn't make a
> >single noise, and the wings deal with most of the wind noise, but the gears
> >on the larger motor do tend to make an annoying fuzz. Maybe I should try and
> >get better gears, made of metal.
>
> Belt drive would be the quietest option.
> Plastic gears, like nylon, are rather quiet.
> Metal gears can be quiet, but only if very well ($$) made.


A decent sized DC motor, say 3" x 5" will
spin that up. Direct drive, no need for gears.
If you get a 24v servomotor from a scrapyard
it should even have an encoder attached for
speed control, or data sync.


> >Of course I considered a disk, but I don't think the 1/8" axis and its 1/2"
> >ball bearings would have lasted long with the added weight.

I think it is more innovative without the
disc. It is transparent so the light seems to
some from thin air. JMHO :o)
-Roman

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2002\01\04@023529 by Robert Rolf

picon face
The upside to using a disk is that the image is NOT transparent, so it's
much clearer. It's also much safer since any unintended contact results in
a scrape or friction burn rather than a finger chop job.
Have you tried holding a carrot in front of your full bore leading edge to see how
neatly your scan arm slices and dices <G>?

The down side to a disk is not so much the weight as it is the turbulent surface
area that gets created. You'll need a more powerful motor for a given RPM.
A disk would also allow you to place your LEDs
at 120 degree radials for tri color display. You can also use more than one
set of a given color (6 or 9 radials for instance) to allow a lower RPM.

Have you also thought about putting you LEDs on the back side of the beam
so that the image is visible from BOTH sides? Right way on both, or mirror
image with the flip of a switch. Permanent mirror image is of course trivial
if you put the corresponding LEDs in series.

Have you thought about stacking clear LEDs so that you can create the illusion
of depth?


Roman Black wrote:
>
> David VanHorn wrote:
> >
> > >
> > >The original motor (the blue one, which is now disconnected) didn't make a
> > >single noise, and the wings deal with most of the wind noise, but the gears
> > >on the larger motor do tend to make an annoying fuzz. Maybe I should try and

Have you tried a bit of thick grease on the gear mesh? The really viscous stuff
does wonders (100wt).

> > >get better gears, made of metal.
> >
> > Belt drive would be the quietest option.

I concur.

{Quote hidden}

As long as your load is balanced, it shouldn't be a problem.

> I think it is more innovative without the
> disc. It is transparent so the light seems to
> some from thin air. JMHO :o)

Saw this sort of thing decades ago at the Seattle Science Center gift shop.
The problem with transparancy is that it is easily washed out by bright
backgrounds. BTW, a 6" diameter spinning LED clock was selling for $1500
back then. He used belt drive and slip rings. The processor
and drive electronics was in the base.

There now seem to be many variations on this theme as commercial knock offs,
although none is as large as what you've done.

> -Roman

Robert

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2002\01\05@042201 by Peter L. Peres

picon face
> There is a british company putting LED displays onto Race Car Wheels for
> advertising - I suppose it's practically the only place that's left to
> put adverts on.

How about a personal 'ad' on your own bicycle wheels (or car wheels but
that's probably illegal).

There is a problem sensing the index here but it can be overcome, on a one
by one situation analysis probably.

Peter

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2002\01\05@044613 by Jinx

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> How about a personal 'ad' on your own bicycle wheels (or car
> wheels but that's probably illegal).
>
> There is a problem sensing the index here but it can be
> overcome, on a one by one situation analysis probably.

Spokes/light/magnets/hall effect

A problem might be other road users. Just today, motorists
at a train derailment here were warned that if they rubber-neck
they'd get instant fines. I wouldn't like to be responsible for
any unnecessary crashes. Also, harking back to LED signs
on car wheels, I still think they're a waste of time unless you're
travelling parallel to the vehicle. Just my 2c

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2002\01\05@063854 by Joris van den Heuvel

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Roman Black wrote:

> A decent sized DC motor, say 3" x 5" will
> spin that up. Direct drive, no need for gears.
> If you get a 24v servomotor from a scrapyard
> it should even have an encoder attached for
> speed control, or data sync.

I disagree. A DC motor has very little efficiency as a relatively low RPM.
Even 300-400 rpm, the current speed, is a very low speed for a normal 3-pole
DC motor. max efficiency lies at 10 to 20 times as high an rpm. The blue
motor I described actually IS a servo with its 4 brushes, 16 poles and a 480
slot encoder and index slot. It draws 2 amps at 15 volts, and it hardly
spins; it runs pretty hot. The motor I added later on (with the gears) draws
3 amps at 3 volts and gets the whole thing moving, without getting warmer.

> I think it is more innovative without the
> disc. It is transparent so the light seems to
> some from thin air. JMHO :o)
> -Roman

And a lot easier to transport!

Robert Rolf wrote:

> The down side to a disk is not so much the weight as it is the turbulent
surface
> area that gets created. You'll need a more powerful motor for a given RPM.

On the contrary, I believe. A flat surfaced disk, for instance made of
plexiglass, has almost no air resistance. My rectangular arm spun almost
twice as fast after I added the paper "wings". Even now it pulses the air as
the arm passes.

> Have you also thought about putting you LEDs on the back side of the beam
> so that the image is visible from BOTH sides?

Not really. The way I use the display, clamped into a light grid or onto a
balcony, viewed from below, it wouldn't be useful.

> Have you thought about stacking clear LEDs so that you can create the
illusion
> of depth?

As a matter of fact I did, but I think the result won't add much to the
already spectacular sight of the display itself. And even if you use clear
leds, the bottom layer will look blurred from certain viewing angles. I'd be
more tempted to try dual color leds.

> Have you tried a bit of thick grease on the gear mesh? The really viscous
stuff
> does wonders (100wt).

The gear mesh is lubricated with car motor oil (it's all I got), but the
problem really is the larger gear. It's just a cheap nylon one, and it's a
little bit a-centric and raspy. The motor's metal gear is nicely made.


_______________

I don't think I'll be working on the display some time soon, as it's in full
working condition right now, and I have more projects on-stack right now
(16x16 audio switch matrix w/ AD75019 chip) But having written the software,
it shouldn't be too hard to make a new one without all the downsides the
current display has. Improvements could/would be for instance:
- Dual color leds from edge to center
- disk carrier
- 220 VAC fan motor (3000 rpm)
- serial interface (current loop or IR) to edit scroll text, set time/date,
upload logos/software etc.

Talk to you later,

Joris.

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2002\01\05@102924 by Roman Black

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Joris van den Heuvel wrote:
>
> Roman Black wrote:
>
> > A decent sized DC motor, say 3" x 5" will
> > spin that up. Direct drive, no need for gears.
> > If you get a 24v servomotor from a scrapyard
> > it should even have an encoder attached for
> > speed control, or data sync.
>
> I disagree. A DC motor has very little efficiency as a relatively low RPM.
> Even 300-400 rpm, the current speed, is a very low speed for a normal 3-pole
> DC motor. max efficiency lies at 10 to 20 times as high an rpm. The blue
> motor I described actually IS a servo with its 4 brushes, 16 poles and a 480
> slot encoder and index slot. It draws 2 amps at 15 volts, and it hardly
> spins; it runs pretty hot. The motor I added later on (with the gears) draws
> 3 amps at 3 volts and gets the whole thing moving, without getting warmer.

If you are worried about power use it makes
sense to use a belt, otherwise i'd look for
a larger 24v servomotor like the 3"x5" one
I mentioned. I have used these and they are
good at that speed, although about 20v 3A
at that load I guess. But a single motor+
inbuilt encoder just seems the best solution
to me.
-Roman

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