Dancing microwave oven numbers?

[raptorthang]

I'm curious as to what the cause and effect is of the following.

If I am chewing something hard like a nut, bite down on an apple, etc., the digital numbers on the microwave oven move up and down in a jittery way...at least that's what my eyes see. However, if I do the same but look at the digital display on a clock, the computer, etc. the numbers are stable and don't appear to move.

What is causing the digital dispaly 'to dance' on the microwave?

The first time I noticed this I thought I was having some wierd vision seizure but then my wife said the microwave numbers also jumped around when she was eating.

[Jens]

Could it be a difference in size? I think that something small will tend to look like it's jumping more than something large.

[Nowhere Man]

Try it with a CRT as well. It has to do with the refresh rate interfering with the vibration of your eyes, or vice-versa. I would bet that the 8-segment characters on the microwave are not on constantly, but are flickering at 60 Hz or so.

I remember it being brought to general notice some years ago but I can't provide any links.

Fred

[raptorthang]

Thanks Nowhere man. That approach didn't even occur to me.

I must have a peanut brittle party. Everyone bite their candy and stare at the microwave clock. Back in the late 60's we had other ways of having fun but we're all old now.

[Studioguy]

I once took one of those big back massagers and held it firmly against the top of my head. The effect it had on my vision was pretty trippy. Everything looked all wavey like the start of a movie dream sequence. One odd thing though was that the actual picture on the television wasn't waving. The whole room had the wave going, but the images on the TV were perfectly proportioned and intact. I figured it was the same sort of thing: some sort of frequency alignment of the scan rate of the TV and the vibration of the massager.

(and yes, I know how odd it sounds that I was holding a back massager against my head...My wife thoroughly explained how odd it was.)

[TrAI]

Try it with a CRT as well. It has to do with the refresh rate interfering with the vibration of your eyes, or vice-versa. I would bet that the 8-segment characters on the microwave are not on constantly, but are flickering at 60 Hz or so.

I remember it being brought to general notice some years ago but I can't provide any links.

Fred

Generaly LED displays uses some sort of scanning/multiplexed approach, either one number on at a time, or some of the segments of each number to reduce the complexity of the circuit or to save outputs on a micro-controller, also a circuit using such an approach will probably use less energy than a constantly driven display would. Quite often the scanning frequency is low enough to be noticed if your eyes move rapidly.

[mahesh]

...I must have a peanut brittle party. Everyone bite their candy and stare at the microwave clock. Back in the late 60's we had other ways of having fun but we're all old now.
Hey raptor....

years ago, I used to have a digital clock, encased in a solid glass cuboid, which displayed the circuitry / wiring of the works. It was a pretty pretty thang.... The LED numbers used to 'dance' too, when looking at them, chewing something.

I would have thought that the movement of aqueous humour in the eye, gives the impression of 'dancing digits'. Too.

well, happy partying on brittles....whatyoucooking!?!?

[samkent]

While I was in Europe, I noticed that the street lamps had a visible flickering. It’s even visible in movies and video sent to the states. They use 50hz, we use 60hz AC power. I wonder why they chose 50hz. At least 60 has a link to time.

[HenrikOlsen]

Stick a bridge rectifier on 50 Hz and you have 100 Hz, nicely decimal.
1/60 second doesn't have any special significance for timekeeping.

[NEOWatcher]

While I was in Europe, I noticed that the street lamps had a visible flickering...
Apparently, this was the reason for Westinghouse's decision. That is if you can trust what wiki says (http://en.wikipedia.org/wiki/Utility_frequency) about something that has urban legends tied to it.

And; as Henrik says, 50 sounds better in metric.