how would you drive 768 servos?

zippyflounder

http://www.smoothware.com/danny/weavemirror.html·yes thats right 768...amazing/

SRLM

Okay. If somebody were to build that using parallax products, they would probably start witht the servo board. Two of them daisychained gives 30 servos per I/O pin. With a BS2, we could get 480 per module.

So:

768 servos
64 servo controllers
64 Power supplies
2 BS2s

That totals up to $2560 for the controllers, $9984 for the servos, $100 for the BS2s, $576 for the power suplies.

Total: $13,220

Expensive...

allanlane5

But ... It's ART!

SRLM

And yours for only $20,000!

Phil Pilgrim (PhiPi)

I think the cheapest way to do t would be to have each motor controlled by it's own micro (e.g. cheap PIC, AVR, or Chinese knockoff). These would then be joined in a daisy-chained serial network through which they receive commands from the central processor. It's unlikely that one would use off-the-shelf modules for a project of this scale. As SRLM has shown, the cost would be enormous.

-Phil

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'Still some PropSTICK Kit bare PCBs left!

allanlane5

Eh-- you could do it with 25 SX48 boards ($250) if you wired 32 servo's to each one, and used one board as the "master".

The price quoted above assumed $13 per servo -- resulting in $10,000 no matter HOW you slice it.

SRLM

The controllers were relatively cheap at $2500...

Phil Pilgrim (PhiPi)

768 Atmel ATTiny13s would cost $622 from DigiKey. These could easily handle both the motor control and communication networking needs.

This is not meant to denigrate the value of ready-made functional modules; only to point out that, at such volumes, mass-production economies are possible from custom-made electronics.

-Phil

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'Still some PropSTICK Kit bare PCBs left!

Zoot

That is startlingly cool.

Here's a servo controller: 84 channels per board (36 can be used for A/D I/O). USB.·Separate battery/power leads for "banks" of servos that might run at different voltages or from different battery packs.·@$126 per, that would be $1152.

http://acroname.com/robotics/parts/R297-SD84.html

Personally, I like PhiPi's idea -- but then they need to be manufactured/built/programmed/etc.

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When the going gets weird, the weird turn pro. -- HST

1uffakind.com/robots/povBitMapBuilder.php
1uffakind.com/robots/resistorLadder.php

SRLM

What about a grid system to control the servos? I seem to remember hearing about old (1960s) RAM chips that were a grid of holes, and electricity was applied horrizontally and vertically to read/write the data. Seems that something like that could be done here...

metron9

Phil has it right but I would use the tiny24's and use 8 servos per chip. Use the 2 wire USI for communication.

So you need 96 chips. You will have 2 extra pins on each chip (led showing communication or errors in communication perhaps?)

I would use DMX protocol.

$111.00 from digikey per 100 chips.

Whip up a board and get it made from pcbcart.com for under 100 bucks.

Then do some homework in China for the servos.

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Think Inside the box first and if that doesn't work..
Re-arrange what's inside the box then...
Think outside the BOX!

zippyflounder

i have a source for servos at 2 bucks a pop........

zippyflounder

SRLM said...
What about a grid system to control the servos? I seem to remember hearing about old (1960s) RAM chips that were a grid of holes, and electricity was applied horrizontally and vertically to read/write the data. Seems that something like that could be done here...

what if we think of the servos as led's where there are only 2 states..on and off.

allanlane5

You COULD build some kind of switch-IC arrangement, to route the Servo control signal to one or a few servo's at once -- but I don't think that would be nearly as cool as most or ALL of the servo's moving at the same time to "whirrr" the picture into existence.

zippyflounder

allanlane5 said...
You COULD build some kind of switch-IC arrangement, to route the Servo control signal to one or a few servo's at once -- but I don't think that would be nearly as cool as most or ALL of the servo's moving at the same time to "whirrr" the picture into existence.

cool or not you only need 2 postions.

SRLM

In the picture the servos had more than two positions, but I think that's probably the easiest way to initiate. Then all you have to do is have a table of 0s and 1s, instead of a table of large values.

zippyflounder

SRLM said...
In the picture the servos had more than two positions, but I think that's probably the easiest way to initiate. Then all you have to do is have a table of 0s and 1s, instead of a table of large values.

i was thinking of one that just didn black or white...2 postions.

Zoot

All of Rozin's work is a kind of opto-mechanical grayscale of sorts. The one piece has 100s of wooden dowels with the endfaces cut at 45 degree angles. The dowels are rotated, and a light shines on them from above. The angle of rotation corresponds to a level of "gray". The weave piece has a grayscale painted or printed across the face of the cylinder -- again the rotation angle will give you a level of gray.

In fact, the programming is not too bad, it's the mechanics... say you have a 27 x 27 grayscale image captured from the camera -- you'd scan through each pixel value (0-255) and rotate the corresponding servo/motor/wheel/dowel. You could grab byte grayscale values from a CMUCam, and you don't really need to "store" anything -- just grab each pixel as it comes in and send it right back out to the servo network.

But that's 729 thingies you gotta build

This guy's work is so cool though I'd love to try something like it.

Zippyflounder -- what's the deal w/your source on cheap servos? Presuming that's a bulk price

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When the going gets weird, the weird turn pro. -- HST

1uffakind.com/robots/povBitMapBuilder.php
1uffakind.com/robots/resistorLadder.php

zippyflounder

Zoot said...
All of Rozin's work is a kind of opto-mechanical grayscale of sorts. The one piece has 100s of wooden dowels with the endfaces cut at 45 degree angles. The dowels are rotated, and a light shines on them from above. The angle of rotation corresponds to a level of "gray". The weave piece has a grayscale painted or printed across the face of the cylinder -- again the rotation angle will give you a level of gray.

In fact, the programming is not too bad, it's the mechanics... say you have a 27 x 27 grayscale image captured from the camera -- you'd scan through each pixel value (0-255) and rotate the corresponding servo/motor/wheel/dowel. You could grab byte grayscale values from a CMUCam, and you don't really need to "store" anything -- just grab each pixel as it comes in and send it right back out to the servo network.

But that's 729 thingies you gotta build

This guy's work is so cool though I'd love to try something like it.

Zippyflounder -- what's the deal w/your source on cheap servos? Presuming that's a bulk price

ya its in lots of 1 k little bugger like they use in the little robots. I want to do a rozin thing but in black and white but smaller dots....hence only 2 postions.

Zoot

OK, so $2000 for 1000 servos. So, uh, where?

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When the going gets weird, the weird turn pro. -- HST

1uffakind.com/robots/povBitMapBuilder.php
1uffakind.com/robots/resistorLadder.php

zippyflounder

Zoot said...
OK, so $2000 for 1000 servos. So, uh, where?

i get them from a old buddy, but have seen them on e bay too just ask for a quote on x number.

Phil Pilgrim (PhiPi)

Aibaba.com is your friend for this kind of stuff — sometimes. Caveat emptor is very much the rule when buying offshore. That said, here are some servo listings.

-Phil

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'Still some PropSTICK Kit bare PCBs left!

SRLM

zippyflounder:

Are you going to build a simplified version of the artwork? I hope you test using something small (2x2 or 3x3) before you invest the thousands in a full scale...

zippyflounder

SRLM said...
zippyflounder:

Are you going to build a simplified version of the artwork? I hope you test using something small (2x2 or 3x3) before you invest the thousands in a full scale...

typicaly you would build modules say 20 by 20