> From:         Lindy Mayfield[SMTP:Lindy.Mayfield@EUR.SAS.COM]
> Sent:         Sunday, May 23, 2004 6:54 AM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Re: [PIC:] Single Row of LED's Illusion - How they do that?

> Hi,

> Thanks for everyone's input on this and please one more thing before
> I let this drop just for my understanding.

> Just looking at the ad for the waving pen that spells out something
> and reading everyone's input on the subject comparing it to a
> dot matrix printer it makes sense to me that the timing of the lights
> has to be synchronized with the position of the wand in
> space.

> So would this mean that in the light pen wand thingy that there is
> some sort of tilt mechanism there that synchronizes the lights
> with the speed it is waving back and forth?

> -----Original Message-----
> From: pic microcontroller discussion list [mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of Howard Winter
> Sent: Sunday, May 23, 2004 12:30
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [PIC:] Single Row of LED's Illusion - How they do that?

> Lindy,

You can eliminate the problem of sensing the wand position, as well as
that of making and waving a wand, if you just put a rotating mirror in
front of the LEDs. The axis of rotation would be parallel to the line
of LEDs. There would be no angular distortion as there would
be with a rotating disk, and the mirror position could be sensed
by detecting the reflected light from a fixed LED. This would give a
synch pulse which would trigger the display sequence. The non-
linearity in the horizontal direction as the mirror rotates could be
taken out in software.

John Power

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