Rotating LED's

[Viewmaster]

Just found this LED site..
Plenty of food for NBTV thought here. An amazing display of all types of rotating LED constructions.
Mini Dynascans.

How about a round NBTV?

http://www.luberth.com/analog.htm
Albert.

[gary]

The link seems to be dead now but this is the best of this type of display I have come across, it is done with just 64 LEDs, and uses polar coordinates to utilise the entire sweep of the LEDs.

[Viewmaster]

The link still works here.
http://www.luberth.com/analog.htm

Your link is interesting.

Thinking aloud....
Converting 32 line std NBTV to a flat rotating display like a clock face has some interesting problems...

Assuming just a single arm carrying LEDs.
When rotating at 6 o/clock the bottom half of the 16th NBTV line only will be shown.
At 12 o/clock the top half of the NBTV 16th line!

At 3 o/clock position just the centre pixels of lines 1 to 15 of NBTV.
At nine o/clock the centre pixels of lines 17 to 32
The in-between positions get very complex, and more LEDs will be required to be working at the intermediate angles of rotation.

Probably done by putting each frame of NBTV into memory and then pick and mix mathematically as required under software control are my initial thoughts on a completely flat rotary NBTV.
Sine or Cosine are going to come in here somewhere as the arm rotates.
Mmmmm.
Albert.

[gary]

No I meant the link to the original RoPod article sorry, I just happened to have kept a copy of the video because I found it very interesting.

Yes the picture is formed by converting from cartesian to polar coordinates, which as you say, will use cosine and sine, thusly:

X= R*cos(Theta)
Y= R*sin(Theta)

RoPod stands for:

Rotating Polar Display

[Viewmaster]

No I meant the link to the original RoPod article sorry,

I should have read your letter more carefully and would have realised you were refering to your link not mine, so I'm sorry!

I tried the ROPOD site and as you say the link to the video is dead. I also tried utube but not there either. It deserves to be shown on the net.
Albert.

[AncientBrit]

From very simple experiments I did on rotating displays the problems we face are that the brightness of an LED off-axis falls off quite rapidly.

So for drum display the outer vertical edges will appear dimmer.

I wonder whether they are using specially adapted LED optics to give a wider viewing angle?

For a small "propeller" display which is viewed face-on this should not be an issue.

Regards,

Graham

[Steve Anderson]

From very simple experiments I did on rotating displays the problems we face are that the brightness of an LED off-axis falls off quite rapidly. So for drum display the outer vertical edges will appear dimmer. Regards, Graham

This effect is slightly visible in Kevin Hadfield's 'carosel' NBTV displays, both mono and colour. I did e-mail Kevin some years ago and he selected LEDs that had a wide dispersion angle. His displays showed four images around the circumference so that from a long distance the LEDs at the vertical edges would be viewed at a 45 degree angle.

I've had no contact with Kevin since and sadly he's not a member of this forum.

http://www.kevinhadfield.co.uk/

Steve A.