Electrically positioned light

[Jeff Johnson]

I have a need for a way to move a light around a geometry(such as on a
circle(not a disk)).

One way would be to have a single LED and "cover" above the led. The cover
has a small hole in it letting the LED light shine through. If hte cover can
be easily positioned then it would produce the effect I want. Because the
cover requires mechanical translation it is more difficult than what I'm
interested in (unless there is some trick to moving such things without
motors/pullys/etc... (I've seen some cool translation devices based on
piezo's somewhere).

In any case what I was thinking about was if there was a way to electrically
position light. Somehow using frequency resonance in 2D on an "led"
plane(I'm just making up stuff here).

Of course I could just use a bunch of LED's but this doesn't give me the
resolution I want, costs a ton, and requires a lot of circuitry.

Basically I just want to move a dot around a small circuit where the angular
position is controlled by an electrical single. Nothing fancy but just
something simple. I'm looking more about if it is theoretically possible
rather than some actual device since I doubt there is anything out there
that does this.

Any ideas how one can achieve this?

Just incase your confused on what I'm asking. You can also think of the
knighrider effect from the car. In my case I want to be able to be able to
have a continuous position(or close) and to be able to use a single signal.

 

[Rich Webb]

I have a need for a way to move a light around a geometry(such as on a
circle(not a disk)).

How precisely does it need to be positioned? What are the consequences
if the position of the light is slightly off? "Hunh, that light is
slightly off" or "Doctor, the patient is dead."

What angular tracking rate do you need? How large of a circle? Dinner
plate or football stadium?

How much light? Visible in room illumination or midsummer Mojave desert?

Making some reasonable assumptions, using hobby-grade servo motors might
do the trick. <http://www.seattlerobotics.org/guide/servos.html> Use a
pair oriented X-Y to directly aim the light source or (slightly harder)
use a fixed light source and the servos to orient a mirror.

 

[Martin Brown]

I have a need for a way to move a light around a geometry(such as on a
circle(not a disk)).

One way would be to have a single LED and "cover" above the led. The
cover has a small hole in it letting the LED light shine through. If hte
cover can be easily positioned then it would produce the effect I want.
Because the cover requires mechanical translation it is more difficult
than what I'm interested in (unless there is some trick to moving such
things without motors/pullys/etc... (I've seen some cool translation
devices based on piezo's somewhere).

In any case what I was thinking about was if there was a way to
electrically position light. Somehow using frequency resonance in 2D on
an "led" plane(I'm just making up stuff here).

Of course I could just use a bunch of LED's but this doesn't give me the
resolution I want, costs a ton, and requires a lot of circuitry.

Basically I just want to move a dot around a small circuit where the
angular position is controlled by an electrical single. Nothing fancy
but just something simple. I'm looking more about if it is theoretically
possible rather than some actual device since I doubt there is anything
out there that does this.

Any ideas how one can achieve this?

Highly collimated LED laser focussed onto the plane of the display wall
and a mirror galvanometer movement. Two of them at right angles and you
can draw simple pictures or patterns as well.

Regards,
Martin Brown

 

[Jeff Johnson]

How precisely does it need to be positioned? What are the consequences
if the position of the light is slightly off? "Hunh, that light is
slightly off" or "Doctor, the patient is dead."

Obviously it won't be used in critical applications but will be viewed so if
it's off more than a few percent it will be obvious.

What angular tracking rate do you need? How large of a circle? Dinner
plate or football stadium?

About an inch square(probably half if I were to actually implement it).

How much light? Visible in room illumination or midsummer Mojave desert?

Making some reasonable assumptions, using hobby-grade servo motors might
do the trick. <http://www.seattlerobotics.org/guide/servos.html> Use a
pair oriented X-Y to directly aim the light source or (slightly harder)
use a fixed light source and the servos to orient a mirror.

This is precisely what I'm trying to avoid. Motor's is the "standard"
solution but expensive and bulky. If there were some way to "position" light
then it be a better solution. There are many possibly solutions but I'm not
sure there are any cheap ones.

The only practical solution I can think of is to use a fixed LED with the
"cover" and hole and position the cover using some means. magnetics could
possibly be used for both the linear and angular 1D case.

I'm looking more for a possible solid state monolithic method or something
that approximates this well. What I'm thinking of is possibly using a
standing wave that has a high resonant peak through a material that response
to it(sorta like an LCD). You basically position the "voltage" along the
material and the material responds to it. Not sure if this would be easily
doable though since it might be difficult or require a lot of circuitry to
create such standing waves.

The main point is that I want something simple. In this case it means few
parts and low cost. Because I'm looking for more of a theoretical solution I
don't mind pretending it is already in production. Obviously with enough
money and techology one can shrink just about anything down to scale and say
it will work. I'm looking for it to be practical too.

Think of a consumer appliance. Generally these have led's. In fact, a simple
digital dB meter would be a good application(although I want mine slightly
smaller than these). These are generally made up of a stack of LED's. I'd
like a way to do this continuously with a simple way to control it. If one
could easily create a standing wave it would be pretty cool to use.

Alternatively maybe one can use a voltage to control the angle of a solid
state device such as an LED by changing some width in it's geometry. This
would be shined on a mirror to increase the length.

Suppose someone showed you a small disk(say about 1cm radius and about 3mm
thick) that had 5 or so pins on the bottom and they were able to use them to
create a small light on the disk and position it anywhere. How would you
think it could be done? Your best guess would be starting with something
solid state. Possibly a very dense array of led's with a controller in it
that translated the voltages into coordinates.

Lets try to get away from a "discrete arary" and "controllers" and come up
with another idea.

 

[Jeff Johnson]

Highly collimated LED laser focussed onto the plane of the display wall
and a mirror galvanometer movement. Two of them at right angles and you
can draw simple pictures or patterns as well.

That would work but might be too costly or not small enough(I'd like to fit
all this stuff in the size of a dim(or slightly smaller). One could probably
use piezo's to position the mirrors(using a "wedge" shape possibly).

Would be nice if there were less of a "mechanical" solution though. LED
based technology should work if one could design an LED to be able to modify
itself. e.g., having a "channel" in the led that could be modified with a
signal which modifies the position of the emitted beam which may use a
mirror to magnify the effective change.

 

[Rich Webb]

Think of a consumer appliance. Generally these have led's. In fact, a simple
digital dB meter would be a good application(although I want mine slightly
smaller than these). These are generally made up of a stack of LED's. I'd
like a way to do this continuously with a simple way to control it.

Maybe eliminate the constraint of a single light source and use one of
the available OLED displays like this
<http://www.crystalfontz.com/product/CFAL9664BFB1.html>?

 

[Jeff Johnson]

Maybe eliminate the constraint of a single light source and use one of
the available OLED displays like this
<http://www.crystalfontz.com/product/CFAL9664BFB1.html>?

While it would be nice to display full pictures I would need something about
half the size(slightly smaller than a dime). I don't really need anything
but to display a movable dot so feel that there is some simple way to do so
although the technology may not be out there.

 

[Jeff Johnson]

Well, you said something about "theoretically possible, I'll shrink it
later". There you are -- use an OLED, or a high-resolution LCD, and
switch pixels on and off. Pretend that it's only active in the ring that
you want, then when later comes have your parts made up with _only_ the
ring active.

Was that suppose to be helpful?

 

[Jeff Johnson]

Yes it was. You're getting answers that are well within the parameters
that you've stated, but you're rejecting everything you've gotten so far.
Quit complaining and start cutting metal, or you'll never get anywhere.

I've explained what I want to do and the only person that seems to get it is
Martin Brown. I said I would like a solid state version. It seems to me you
need to stop wasting peoples time and go "cut metal" yourself.

 

[Martin Brown]

That would work but might be too costly or not small enough(I'd like to
fit all this stuff in the size of a dim(or slightly smaller). One could
probably use piezo's to position the mirrors(using a "wedge" shape
possibly).

A dime is what about 1cm diameter x 1mm thick. I can't see you being
able to do it without enormous expense miniaturising things.

The buds for walkman should provide you with small cheap voice coils and
mechanics and a bit of mylar film on one of them would be a start.

Would be nice if there were less of a "mechanical" solution though. LED
based technology should work if one could design an LED to be able to
modify itself. e.g., having a "channel" in the led that could be
modified with a signal which modifies the position of the emitted beam
which may use a mirror to magnify the effective change.

Other options would be a pair of narrow slits at a shallow angle so that
a small linear shift perpendicular to the slits moves the crossing point
where light gets through a long distance.

If you described why you wanted to do this it might be possible for
others to suggest something more appropriate.

Regards,
Martin Brown

 

[Rich Grise]

Just incase your confused on what I'm asking. You can also think of the
knighrider effect from the car. In my case I want to be able to be able to
have a continuous position(or close) and to be able to use a single
signal.

Pivoted mirrors driven by a speaker voice coil?

Hope This Helps!
Rich

 

[Rich Grise]

This is precisely what I'm trying to avoid. Motor's is the "standard"
solution but expensive and bulky. If there were some way to "position"
light then it be a better solution. There are many possibly solutions but
I'm not sure there are any cheap ones.

The only practical solution I can think of is to use a fixed LED with the
"cover" and hole and position the cover using some means. magnetics could
possibly be used for both the linear and angular 1D case.

These two paragraphs are mutually exclusive.

Good Luck!
Rich

 

[Jeff Johnson]

I know some hand-stuff PCB stuffing operations use a LED to point to
where the part goes on the circuit board.
Then, the workers grab the part and insert it. Later, it's off to the
waveflow...
Is this what you're talking about?

I don't understand your comment: "Basically I just want to move a dot
around a small circuit..."
What small circuit?

Anyway, another idea (maybe?) is I've seen those "LED clocks" for lack
of a better description.
They have this rotating or oscillating "stick" and embedded in the
stick is a bunch of LED's.
As the stick rotates (rapidly), the LED's turn on or off based on
their angular position.
The human eye "translates" these on/off LED's vs. time & position into
legible clock readout (or text, etc...)

Otherwise, I'm afraid I don't know what you're looking to do.
Some other posters have mentioned OLED, and that could be reasonable
(in terms of $$ and headaches), but again, not clear on your desired
outcome.

Either the light source must move, or the target must move (or both).
Either option may include mirrors, etc...
The only other option I see is to use multiple light sources.

Not necessarily. Obviously using todays technology that is the only way
have.

I'm interested in a new way using current theory to develop something more
practical. It is really more of a thought experiment about something I would
use in practice if it were out.

The idea is to use current technology to create exactly what I'm looking for
rather than using current products to create something that isn't.

As I pointed out in some post, suppose you want to create a dot on a small
screen and be able to move it around continuously(or almost). How would you
tackle this? What if no moving parts and only a few signal lines can be
used? What if no complex controller and/or driver can be used? What does
this mean? For starts it means you have to probably come up with some base
material to use that will you can manipulate to do what you want. (This is
probably why some are having such trouble with this question).

The best thing I can do is offer my line of thinking(theoretically valid or
not):

Take a rectangular piece of light emitting semiconductor. Send a pulse down
it along the anode channel(think of it as just a stretched out LED). As the
pulse is traveling down the anode channel the voltage across the diode is
larger at that location.

* < pulse
-------------------- < anode

-------------------- < cathode connected to ground

from * to ground the voltage is high. Therefore the local region of this led
should emit light rather than the whole channel. It will depend on the pulse
size in some way and unfortunately travel at the speed of light.

In this case we get a "kightrider" effect as the light moves from left to
right with the pulse. Probably on far to small of a scale to see. This
should work in theory I believe without much problem besides scale. One end
of the anode would probably be connected to ground through a resistor. You
can think of it being like a transmission line.

If we were able to setup a standing wave with a single resonant peak and
control it's position then we could control the position along the LED
strip. I'm not sure if this is even theoretically possible to do but maybe
some adaptation could work.

This uses current theory and technology for the device but may require a
complex control circuit for setting up standing waves if it is possible to
do so.


Another possible way would be to use the similar concept above but have a
movable jumper between the vcc and the anode. The moveable jumper's position
could be controlled by a voltage which would accellerate it and it's
position could be computed and should be rather predicable(or some feedback
could be used). This would be more of a mems application though and I'm not
sure of hte lifespan of the jumper or sliding contacts.


-------------------- < Vcc
* < jumper
-------------------- < anode

-------------------- < cathode connected to ground


Anyways, I'm sure there are other ideas that would "work" too. Theoretically
this stuff should "work" as there is nothing advanced here. Just basic
physics and electronics. If it did work well then it wouldn't be hard to
create(not much harder than a normal LED, which I guess is pretty easy).

These also work on the small scale and can be used a wide range of 1D
geometries with low power consumption and size.

 

[Grant]

Look at miniature projection TV device, half a million tiny mirrors on a chip,
electrostatically positioned. Motorola?

Grant.