[Quack]

Hi,

I am looking into building a spinning LED display, and would be
interested in any suggestions anyone may have

This display will be 100 led's tall (or more if possible), and sealed
in a glass/perspex cylinder, of about 15cm diametre.
so quite different from the usual 'glass ball' versions around the
place.
The purpose of this display is to vertically list 10 2 digit numbers,
and if possible animate them as new numbers 'come in'.

I am wondering if there is some reason all the existing versions are
glass
balls. possible reasons i can think of;

-because the spherical glass helps to magnify the display area
-to maintain a low force on the motor, as something taller would be
heaver
-to be quieter, as the heaver the spinning part, the more motor power
and the noisier it would be
-too much wear on moving parts
-the effects of 'persistence of vision' are not as apparent on
something taller perhaps, and would need to spin much faster... hmm,
possibly but i dont think so.

Okay, assuming that noise is no problem and a magnified display area
is not required and the effects of 'persistence of vision' are still
applicable in a tall display of around the same RPM, then moving on
.

Ways to communicate to the spinning LED modules in the cylinder;

-RF communications (fastest ?)
-Optical (using each revolution as a kind of serial clock, and
clocking in X bits, where each bit is a LED/Photodiode pair, the
photodiode being on the spinning surface)
-serial communications through the 'shaft' of the motor, apparently
only reliable at 4800bps (seen here
http://www.seattlerobotics.org/encoder/200112/srs.htm)

Any suggestions or experiences anyone would like to share ?

Alex.

 

[Anders F]

I am looking into building a spinning LED display


Ways to communicate to the spinning LED modules in the cylinder;

-RF communications (fastest ?)

Kind of a overkill I think ;-)

-Optical (using each revolution as a kind of serial clock, and
clocking in X bits, where each bit is a LED/Photodiode pair, the
photodiode being on the spinning surface)

Or a plain modulated beam (IR ie.) to a receiver or two near the center of
the spinner...

/A

 

[Marcello]

I'm bulding a similar machine and using Ir communication.
Consider that IrDA standards tell that you can reach 16Mb/s, a speed
that you cannot reach with RF devices.
I put a receiving led in the rotation axe
I'm still working on the communication
I had no problem in transmitting signals 'till 9600 bps but now I took
a break since, using IrDA devices I decided to study IrDA protocol so
that I can use the standard in my devices and conserve this acquired
know how for future applications

bye
Marcello

 

[Kryten]

Ways to communicate to the spinning LED modules in the cylinder;

IR link sounds easiest (using simple protocol like used by TV handsets).

An inductive loop would be okay too, if you don't mind a little coil
winding.

 

[Spehro Pefhany]

Hi,

I am looking into building a spinning LED display, and would be
interested in any suggestions anyone may have

This display will be 100 led's tall (or more if possible), and sealed
in a glass/perspex cylinder, of about 15cm diametre.

The biggest I've seen stands over 6' (2m) tall and shows full color.
It's fairly quiet.

so quite different from the usual 'glass ball' versions around the
place.
The purpose of this display is to vertically list 10 2 digit numbers,
and if possible animate them as new numbers 'come in'.

Seems like an awful lot of trouble to me, compared to static LED
numerical displays, but it's your project.

I am wondering if there is some reason all the existing versions are
glass
balls. possible reasons i can think of;

They are not (see above).

-because the spherical glass helps to magnify the display area
-to maintain a low force on the motor, as something taller would be
heaver
-to be quieter, as the heaver the spinning part, the more motor power
and the noisier it would be
-too much wear on moving parts
-the effects of 'persistence of vision' are not as apparent on
something taller perhaps, and would need to spin much faster... hmm,
possibly but i dont think so.

Okay, assuming that noise is no problem and a magnified display area
is not required and the effects of 'persistence of vision' are still
applicable in a tall display of around the same RPM, then moving on
.

Ways to communicate to the spinning LED modules in the cylinder;

-RF communications (fastest ?)
-Optical (using each revolution as a kind of serial clock, and
clocking in X bits, where each bit is a LED/Photodiode pair, the
photodiode being on the spinning surface)
-serial communications through the 'shaft' of the motor, apparently
only reliable at 4800bps (seen here
http://www.seattlerobotics.org/encoder/200112/srs.htm)

Any suggestions or experiences anyone would like to share ?

Alex.

You could look at sliprings. Some are very low noise, but tend to be
expensive new. You're going to need something like that to get the
power to the rotating circuitry. You could look at capacitive coupling
of the signals (kind of a non-contact slipring), which could be
homemade (assuming you have access to basic machine tools). Perhaps
differential signals. For optical, you could use a few sensors and
just use an asynch serial prototcol.


Best regards,
Spehro Pefhany

 

[Guy Macon]

I am puzzled as to why anyone would care about the data rate to the
spinning portion. The obvious solution is the have a uP on the part
that spins and to send fairly high level commands to it.

 

[Ian Stirling]

I'm bulding a similar machine and using Ir communication.
Consider that IrDA standards tell that you can reach 16Mb/s, a speed
that you cannot reach with RF devices.

802.11turbo - 108Mb/s.

 

[Quack]

I am puzzled as to why anyone would care about the data rate to the

spinning portion. The obvious solution is the have a uP on the part
that spins and to send fairly high level commands to it.

It would be nice to have it as a host-controlled display, much like a
standard LED or even LCD screen. More Dynamic etc.

But in my case, your right, it could be made such that only high level
commands get sent, and all animation/font data etc is stored on the uP
on the spinning board.

But i would like to keep this cylinder as 'see-through' as possible,
and the less circuitry i can have on the shaft, the better it will
look i think.

Alex.

 

[Quack]

-Optical (using each revolution as a kind of serial clock, and

Or a plain modulated beam (IR ie.) to a receiver or two near the center of
the spinner...

What if i used a single IR receiver on the spinning portion, and a
ring of evenly spaced IR leds (in parallel) under/around it, perhaps 4
transmitters, so that in any given position, the receiver gets a good
IR beam.

Hmm.. that sounds pretty simple. thanks

Alex.

 

[Quack]

I'm bulding a similar machine and using Ir communication.
Consider that IrDA standards tell that you can reach 16Mb/s, a speed
that you cannot reach with RF devices.
I put a receiving led in the rotation axe
I'm still working on the communication
I had no problem in transmitting signals 'till 9600 bps but now I took
a break since, using IrDA devices I decided to study IrDA protocol so
that I can use the standard in my devices and conserve this acquired
know how for future applications

Great! i'd love to know more about what your building, maybe we can
share a few things ... Is that your correct email address ?

Alex.

 

[Quack]

An inductive loop would be okay too, if you don't mind a little coil

winding.

What kind of speeds do you think i could get through something like that ?

Alex.

 

[Quack]

The biggest I've seen stands over 6' (2m) tall and shows full color.

It's fairly quiet.

Wow!, got any links to something like that ? where is it, who made it

Seems like an awful lot of trouble to me, compared to static LED
numerical displays, but it's your project.

Yes, definantly more trouble. But its for a very special environment
where the sexier it looks, the better .

Also the 360' viewing is a major advantage over current systems in
place.
(numbers will slowly rotate, or print out the numbers on 2 points,
then rotate slowly)

You could look at sliprings. Some are very low noise, but tend to be
expensive new. You're going to need something like that to get the
power to the rotating circuitry.

Is there any other way to power it ? This page shows a simple
modification to a motor to accomplish that
(http://www.seattlerobotics.org/encoder/200112/srs.htm). But it may
not be reliable, and is probably a close approximation to what your
talking about.



Alex.

 

[Frank Bemelman]

Wow!, got any links to something like that ? where is it, who made it

Here's one:
http://www.act-thielmann.at/360Video/

I saw these on Schiphol Airport in Amsterdam. They are very
bright. The whole contraption does vibrate a bit, and a little
bit of noise but okay for use in public areas.

[snip]

 

[Spehro Pefhany]

Wow!, got any links to something like that ? where is it, who made it

It was developed by an Asian (Singapore, Hong Kong or Taiwan) company
ca. 2002. Try a google search- it won't be trivial. My info is
dead-tree and archived- not inexpensive to get to.

Yes, definantly more trouble. But its for a very special environment
where the sexier it looks, the better .

Also the 360' viewing is a major advantage over current systems in
place.
(numbers will slowly rotate, or print out the numbers on 2 points,
then rotate slowly)


Is there any other way to power it ? This page shows a simple
modification to a motor to accomplish that
(http://www.seattlerobotics.org/encoder/200112/srs.htm). But it may
not be reliable, and is probably a close approximation to what your
talking about.
Alex.

Check out Bob Blick's propellor clocks as well.


Best regards,
Spehro Pefhany

 

[Marcello]

Great! i'd love to know more about what your building, maybe we can

share a few things ... Is that your correct email address ?

no
if you want you can write me at
marcellotisca
at
tiscali
dot
it