Hard drive POV clock. Can anyone make heads or tails of this inscrutables article?

Thread Starter

spinnaker

Joined Oct 29, 2009
7,835
Some of those folks on inscrutables have some pretty cool ideas. A few do a very good job of explaining how they did the project but most do a horrible job.

Can anyone make heads or tails of this Indestructible article?

https://www.instructables.com/id/Recycled-Hard-Drive-Clock-FuneLab/

The project is based of of a POV method similar to that used in some of the original mechanical televisions.

He mentions two versions of the clock. A simple version and one that shows numbers. But he doesn't mention anywhere in the article of how he does the numbers!

I think I have an idea. If you look closely at the one photo it shows a disk with holes. The photo is not real clear but the best I can figure is you would have a hole for each row. There would be one hole per column. The MCU would light an LED at the appropriate time. So for example if you had 8 holes and did want to show a straight line, the LED would light 8 times all with a delay between illumination to give the appearance of a straight line.

Does this sound like a plausible explanation of how it is done?
 
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Papabravo

Joined Feb 24, 2006
13,534
Some of those folks on Indestructibles have some pretty cool ideas. A few do a very good job of explaining how they did the project but most do a horrible job.

Can anyone make heads or tails of this Indestructible article?

https://www.instructables.com/id/Recycled-Hard-Drive-Clock-FuneLab/

The project is based of of a POV method similar to that used in some of the original mechanical televisions.

He mentions two versions of the clock. A simple version and one that shows numbers. But he doesn't mention anywhere in the article of how he does the numbers!

I think I have an idea. If you look closely at the one photo it shows a disk with holes. The photo is not real clear but the best I can figure is you would have a hole for each row. There would be one hole per column. The MCU would light an LED at the appropriate time. So for example if you had 8 holes and did want to show a straight line, the LED would light 8 times all with a delay between illumination to give the appearance of a straight line.

Does this sound like a plausible explanation of how it is done?
Is calling them "Indestructables" an attempt at wry humor, or was it just a simple typo? Inquiring minds want to KNOW! NOW!
 

Sensacell

Joined Jun 19, 2012
2,567
Yes- the digital numeric version has multiple independent LED's in baffled compartments behind the rotating disk.
A staggered row of holes arranged in a radial spiral creates the character.

The slotted version is obviously a different animal.
 

Thread Starter

spinnaker

Joined Oct 29, 2009
7,835
Yes- the digital numeric version has multiple independent LED's in baffled compartments behind the rotating disk.
A staggered row of holes arranged in a radial spiral creates the character.
.

Compartments? I didn't read it that way but if they didn't do it that way it sure would be an improvement. I wonder how you would create those compartments?? Cut pieces of Lexan maybe, epoxied in place?

I don't think multiple rows of LEDs would be needed do you? Just a ring of LEDs around the perimeter.


A spiral you say? Would it need to be a spiral? If so why? I do know that is how the mechanical televisions where supposed to be done but I can't seem to wrap my head around what that would look like exactly. Do you know of an example?


I am guessing something like this (crude example) Would not work because it is a circle we are actually dealing with?

upload_2017-12-25_22-11-53.png
 

nsaspook

Joined Aug 27, 2009
7,184
Compartments? I didn't read it that way but if they didn't do it that way it sure would be an improvement. I wonder how you would create those compartments?? Cut pieces of Lexan maybe, epoxied in place?

I don't think multiple rows of LEDs would be needed do you? Just a ring of LEDs around the perimeter.


A spiral you say? Would it need to be a spiral? If so why? I do know that is how the mechanical televisions where supposed to be done but I can't seem to wrap my head around what that would look like exactly. Do you know of an example?


I am guessing something like this (crude example) Would not work because it is a circle we are actually dealing with?

View attachment 142451
You can extract the 2D profile of a image (a Ion beam in this application) with a spinning disk (nipkow disc) with a radial spirals and a timed current collector sampler behind it. The inner holes on this example are for beam profiling using this method.


You can generate an image the same way using the spin of the disk hole pattern to a timed light source using a line scanner.
https://en.wikipedia.org/wiki/Nipkow_disk
 

Thread Starter

spinnaker

Joined Oct 29, 2009
7,835
You can extract the 2D profile of a image (a Ion beam in this application) with a spinning disk (nipkow disc) with a radial spirals and a timed current collector sampler behind it. The inner holes on this example are for beam profiling using this method.


You can generate an image the same way using the spin of the disk hole pattern to a timed light source using a line scanner.
https://en.wikipedia.org/wiki/Nipkow_disk

Yes I am familiar with the nipkow disc . I alluded to it with mentioning mechanical TV. But I have never seen an actual disc not have I seen how to make the spiral, with spacing and all.
 

Sensacell

Joined Jun 19, 2012
2,567
Compartments? I didn't read it that way but if they didn't do it that way it sure would be an improvement. I wonder how you would create those compartments?? Cut pieces of Lexan maybe, epoxied in place?

I don't think multiple rows of LEDs would be needed do you? Just a ring of LEDs around the perimeter.


A spiral you say? Would it need to be a spiral? If so why? I do know that is how the mechanical televisions where supposed to be done but I can't seem to wrap my head around what that would look like exactly. Do you know of an example?


I am guessing something like this (crude example) Would not work because it is a circle we are actually dealing with?

View attachment 142451

If you watch the video with the "etched number" clock, you can see the compartments at one point when they have the disk off.
With the spiral holes trick, each digit compartment has to be narrower than the hole pitch, so only one hole passes over the compartment at any instant.
 

Thread Starter

spinnaker

Joined Oct 29, 2009
7,835
If you watch the video with the "etched number" clock, you can see the compartments at one point when they have the disk off.
With the spiral holes trick, each digit compartment has to be narrower than the hole pitch, so only one hole passes over the compartment at any instant.

But what does the spiral look like? And how would you go about making all of those compartments? I would think you would just need one compartment per LED and it could be as wide as the LED. As long as the spacing between holes is the distance of an LED width. Maybe that is what you meant by pitch?
 

Thread Starter

spinnaker

Joined Oct 29, 2009
7,835
It looks like the one with a slot uses a rim of LEDs and depends on reflection. Where the etched digit one uses 3 leds that face the platter. Probably get a much brighter display with that.
 

nsaspook

Joined Aug 27, 2009
7,184
I've made a simple display from mainly junk and leftover parts to play with using reflective patterns on the platter.
Single strip of white tape of the surface.
The cell phone camera is causing most of the flashing artifacts on the video.

pic18f1320 xc8 code.
https://github.com/nsaspook/hd_pov.git
 
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