Hey, Y'all check this out!

Chuck(G) · Post by **Chuck(G)** » Tue May 24, 2005 3:00 am

Same thing happens with the TV. But it's not your optic nerves vibrating, it's your head. You'd see the same effect if you sat on a paint mixer.

Of course, the same thing happens with me quite often without a tuba (I have CN).

Chuck(G) · Post by **Chuck(G)** » Tue May 24, 2005 3:23 am

tubafreaks7 wrote:How does shaking your head only effect the appearance of the led's and not everything else?

It's actually very simple. All of those LED's are not on all of the time--they're mulitplexed so only one is on at any one time. Normally, your persistance of vision masks the effect. But when your head (or eyes) are moving, the LED lights up in a slightly different spatial location. So you begin to see the on-off effect.

Same with TV--it's really only a little bright dot retracing the screen 60 times per second. Normally, this would be invisible due to persistance of vision. But when your visual field is displaced just a bit, you notice the effect.

Try looking at your LED clock or TV through the blades of a rotating fan. The fan blocks enough of what your eyes see so that your persistance of vision doesn't mask the repetitive cycle--and you see weird flickerings or patterns.

Sitting on a paint shaker will do the same thing.

I can tell an LED traffic light from two blocks away--it flickers very noticeably for me.

OTOH, I LOVE LCD displays! They're so steady!

Dan Schultz · Post by **Dan Schultz** » Tue May 24, 2005 5:04 am

When I play any Ab on my Eb helicon at Shrine Band, all of the percussion instruments vibrate!

punk_tuba · Post by **punk_tuba** » Tue May 24, 2005 10:52 am

yea...i've noticed this

if you play low Bb it vibrates the most.

is this due to the lack of resistance???

i thought i was the only one who noticed this

ahhh......weird

DaTubaKid · Post by **DaTubaKid** » Tue May 24, 2005 4:58 pm

My philosophy: If you can still see the music, then you aren't playing loud enough.

Actually, it's only happened to me a couple of times where I've been playing so loud in my low register that the music has become blurry.

I've noticed the same thing happening with my computer screen though. I tend to do some buzzing while I'm online, and when I'm buzzing pretty low, the screen starts wobbling. Kind of interesting to watch.

Rick Denney · Post by **Rick Denney** » Tue May 24, 2005 5:48 pm

tubafreaks7 wrote:Mr.(G), I bet you'd make a great contestant on Jeopardy!

The tricky part is pushing the button fast enough on the questions where you know the answer.

Rick "who once contemplated a run at Jeopardy, but who is now too slow and too ignorant of pop culture--and Shakespeare" Denney

Rick Denney · Post by **Rick Denney** » Tue May 24, 2005 5:53 pm

Chuck(G) wrote:I can tell an LED traffic light from two blocks away--it flickers very noticeably for me.

Some flicker more than others. The refresh rate should be set rather high in the specs. The old neon pedestrian signals were pretty bad, though.

Traffic people don't know how to measure refresh rate in a typical factory test. I was testing the refresh rate of LED-based dynamic message signs, and used my digital camera. By sweeping the camera across the front of the sign from a distance of about 10 inches, I could cause the flickers to spread across the image. I used a 1/4-second shutter speed, and counted the number of LED ghosts in the image. Once sign was 72 Hz (the spec called for 100 but the customer accepted it anyway), and another company claimed their LED's were not pulsed at all. I didn't believe them, but sure enough the LED smeared smoothly across the image. Most impressive. That's a DMS that would not bother you.

Rick "who thinks you'll have to get used to LED signal indications" Denney

Dan Schultz · Post by **Dan Schultz** » Tue May 24, 2005 6:08 pm

Rick Denney wrote:
Chuck(G) wrote:I can tell an LED traffic light from two blocks away--it flickers very noticeably for me.
Some flicker more than others. .....

Sometimes the flickering of just plain old 60 cycle lighting drives me nuts! Especially some florescent lighting.

Chuck(G) · Post by **Chuck(G)** » Tue May 24, 2005 7:07 pm

TubaTinker wrote:
Rick Denney wrote:
Chuck(G) wrote:I can tell an LED traffic light from two blocks away--it flickers very noticeably for me.
Some flicker more than others. .....
Sometimes the flickering of just plain old 60 cycle lighting drives me nuts! Especially some florescent lighting.

Why the heck would anyone want to be on Jeopardy or any other television program, for that matter? I cherish being a private figure. The game's also too subject to rigging. If they didn't like me, they'd have a category like "Lyrics to rap songs" and I'd be toast.

When I worked in the steel mills during my college years, a goodly part of the plant was wired with 25Hz AC. Huge transformers and motors in comparison to their 60Hz equivalents, but you could just make out the flicker in incandescent lighting. When management converted to mercury-vapor lighting, it was hideous when it was run from 25Hz..

OTOH, I collaborated wtih a plant electrician and got the shop lincandescent ighting wired to the 250VDC that was used to power the overhead cranes and welding equipment. That WAS nice.