[dorkbotdc-blabber] Re: LED Cube Workshop - use an Arduino?
R. Mark Adams, Ph.D.
rmadams at epotential.com
Sat Dec 8 20:22:53 EST 2007
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Okay- I think I have a way to get the Arduino to run the LEDs without
needing anything fancy (read shift registers, etc.) Now I need a way to
test it, and I do not have enough LEDs. Someone (Tim?) had mentioned
that they buy LEDs on ebay and have good luck doing so- any suggestions
as to a vendor, delivery time and price? I figured it might be the best
way to get some quickly to we can test out our ideas! :-)
Thanks-
Mark
Tim Slagle wrote:
> I know you would want to use Make: stuff when possible but there
> are hundreds of Arduinos in stock at AdaFruit:
> http://www.adafruit.com/index.php?main_page=index&cPath=17
> SparcFun also has them:
> http://www.sparkfun.com/commerce/product_info.php?products_id=666
>
> I think the AdaFruit BoArduino would be the thing to use
> however, then the transistor drive circuits and LED column
> connections can just be plugged in to the protoboard without
> soldering:
> http://www.adafruit.com/index.php?main_page=product_info&cPath=19&products_id=72
> Lots of those in stock also, but they are sold as kits and would
> need to be soldered up. No harder than building a MiniPOV kit
> and more useful in the future...
> --Tim
>
>
> --- adam koeppel <koeppel at gmail.com> wrote:
>
>
>>I probably have time, but maybe not the skill. Also, MAKE
>>store is
>>currently out of Arduinos... Damn holiday season... I love
>>the idea
>>of everyone having an Arduino for this and future projects.
>>
>>On 12/6/07, Alberto Gaitán <alberto.gaitan at gmail.com> wrote:
>>
>>>This is a great idea. Especially because everk
>>
>>self-respecting maker
>>
>>>needs an Arduino. I'm pretty sure I don't have the time for
>>
>>this
>>
>>>conversion. If none of you do, either, perhaps we can
>>
>>recruit someone
>>
>>>else from the greater list?
>>>
>>>The Arduino uses Processing as its language and it's pretty
>>
>>well
>>
>>>documented. Haven't looked at the WinAVR C code and don't
>>
>>know how many
>>
>>>lines o'code it has but someone with some chops could make
>>
>>short shrift
>>
>>>of it. Can't be too long.
>>>
>>>Anyone else have the time to do this?
>>>
>>>Alberto
>>>
>>>
>>>
>>>On 12/6/07 4:07 PM, Tim Slagle wrote:
>>>
>>>>Thanks for the offer, but now that I think of it I have
>>
>>some AVR
>>
>>>>prototyping boards that could be used instead of the
>>
>>MiniPOV kit
>>
>>>>for my experimental purposes.
>>>>
>>>>This may complicate things even more, but instead of using
>>>>hacking the MiniPOV kit the LED cube could be driven from
>>
>>an
>>
>>>>Arduino. Someone would just have to convert the software
>>
>>from
>>
>>>>WinAVR C to Arduino's Java-style code. Then commercial
>>
>>Arduinos
>>
>>>>could be bought, or kits could be made. If people
>>
>>bought
>>
>>>>assembled Arduinos they could focus on making the LED cube
>>
>>at
>>
>>>>the meeting. And their Arduino could be the basis of
>>
>>future
>>
>>>>Make:DC projects as well.
>>>>
>>>>I would tentatively volunteer to do the software
>>
>>conversion but
>>
>>>>if there is someone else with more confirmed free time it
>>
>>might
>>
>>>>be better. The Make: 3D cube C code could also just be
>>
>>burned
>>
>>>>into the Arduino CPU (blowing away the bootloader etc) as
>>
>>a
>>
>>>>backup plan.
>>>>--Tim
>>>>
>>>>
>>>>
>>>>--- adam koeppel <koeppel at gmail.com> wrote:
>>>>
>>>>
>>>>>Hi Tim,
>>>>>
>>>>>I ordered a POV kit earlier to play around with. I
>>
>>figured it
>>
>>>>>would
>>>>>not supply enough currents for a massive array. Your
>>>>>transistor
>>>>>solution should work fine. If you want to play around
>>
>>with
>>
>>>>>any of
>>>>>your ideas prior to the meeting, I will let you know when
>>
>>I
>>
>>>>>have
>>>>>assembled the kit. I would be happy to share it as a
>>>>>"testing" unit
>>>>>so we don't have to complicate the group order.
>>>>>
>>>>>Cheers,
>>>>>
>>>>>Adam
>>>>>
>>>>>
>>>>>On 12/6/07, Tim Slagle <tim at slagle.org> wrote:
>>>>>
>>>>>>Sign me up for a kit, but I would probably want it
>>
>>before
>>
>>>>>the
>>>>>
>>>>>>meeting so I can put it together in advance. If other
>>>>>
>>>>>people
>>>>>
>>>>>>want to do this it will complicate the logistics of a
>>
>>volume
>>
>>>>>>order I'm afraid.
>>>>>>
>>>>>>Also, the circuit that drives the cube is a hack, and
>>>>>
>>>>>probably
>>>>>
>>>>>>wouldn't work too well to drive multiple cubes without
>>>>>>additional parts. The cube is driven as three
>>
>>multiplexed
>>
>>>>>>planes of 3x3=9 LEDs. The LEDs in a plane are driven
>>>>>
>>>>>directly
>>>>>
>>>>>>from the AVR uC pins, which is okay, since they can
>>
>>drive
>>
>>>>>about
>>>>>
>>>>>>25mA. But then the planes are addressed by pulling the
>>>>>
>>>>>current
>>>>>
>>>>>>from the whole 9 LEDs into a single AVR uC pin, which is
>>
>>a
>>
>>>>>lot
>>>>>
>>>>>>more current than the AVR can sink. So, the cubes will
>>>>>
>>>>>already
>>>>>
>>>>>>be operating at ~1/27th the brightness of a directly
>>
>>driven
>>
>>>>>LED,
>>>>>
>>>>>>and adding more cubes in parallel would only make them
>>>>>
>>>>>dimmer.
>>>>>
>>>>>>One change that could be easily done to increase
>>
>>brightness
>>
>>>>>is
>>>>>
>>>>>>use two AVR pins in parallel to sink current from the
>>>>>
>>>>>planes. I
>>>>>
>>>>>>think there are enough extra I/O pins to do this for the
>>>>>
>>>>>3x3x3
>>>>>
>>>>>>cube. The firmware would then have to be changed to set
>>
>>two
>>
>>>>>>bits instead of one to address the planes, but this
>>
>>should
>>
>>>>>not
>>>>>
>>>>>>be a big deal.
>>>>>>
>>>>>>A better approach would be to drive the planes through a
>>>>>>transistor that could sink more current. This would
>>
>>require
>>
>>>>>>soldering three ~1Kohm resistors and 2N3904 or 2N2222
>>
>>NPN
>>
>>>>>>transistors to the plane drive I/O pins, and inverting
>>
>>the
>>
>>>>>bit
>>>>>
>>>>>>values of the pins in the firmware.
>>>>>>
>>>>>>I would recommend making the LED cubes on a piece of
>>
>>perf
>>
>>>>>board
>>>>>
>>>>>>if possible, so there would be room to wire up the drive
>>>>>>transistors on the board and you wouldn't have to solder
>>>>>
>>>>>them
>>>>>
>>>>>>directly to the POV kit. But then, I think like an
>>
>>engineer
>>
>>>>>:-)
>>>>>
>>>>>>Mark, if you make the LED grid assembly fixtures, space
>>
>>the
>>
>>>>>LEDs
>>>>>
>>>>>>at some multiple of 0.1" so they will fit on a
>>
>>perfboard.
>>
>>>>>They
>>>>>
>>>>>>need to be less than 1" apart so I'd say make them 0.7"
>>
>>or
>>
>>>>>so.
>>>>>
>>>>>>One variation I've been thinking about that would be
>>
>>cool
>>
>>>>>(but
>>>>>
>>>>>>require more firmware changes) would be to use bi-color
>>>>>
>>>>>LEDs.
>>>>>
>>>>>>As long as the drive voltage is kept around 3V and
>>
>>two-pin
>>
>>>>>>reverse-connected LEDs are used, they could just be
>>
>>wired up
>>
>>>>>>like the single-color cube. Then in the software, the
>>
>>I/O
>>
>>>>>pins
>>>>>
>>>>>>for inactive planes are set to be high-impedance inputs
>>
>>so
>>
>>>>>no
>>>>>
>>>>>>current will flow, and the active plane is set high to
>>>>>
>>>>>address
>>>>>
>>>>>>one color and low to address the other color. So the
>>
>>matrix
>>
>>>>>>would be scanned like six planes of 3x3 with only one
>>
>>color
>>
>>>>>on
>>>>>
>>>>>>at a time. The plane bit values for the high-level
>>>>>
>>>>>addressed
>>>>>
>>>>>>color would have to be inverted since they are now
>>
>>active
>>
>>>>>low.
>>>>>
>>>>>>I will try to buy some bipolar bi-color LEDs for my own
>>
>>use
>>
>>>>>but
>>>>>
>>>>>>others may want them as well...
>>>>>>--Tim
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>--- adam koeppel <koeppel at gmail.com> wrote:
>>>>>>
>>>>>>
>>>>>>>Yeah, if this works out well, it could be an
>>
>>installation
>>
>>>>>>>worthy
>>>>>>>piece. I definitely think the working towards a
>>
>>massive
>>
>>>>>>>assembly
>>>>>>>approach is a good idea, and it will solve the shortage
>>
>>of
>>
>>>>>POV
>>>>>
>>>>>>>kit
>>>>>>>problem. We should probably do a little design work
>>
>>ahead
>>
>>>>>of
>>>>>
>>>>>>>time to
>>>>>>>make sure a single POV kit can provide the power we
>>
>>need,
>>
>>>>>>>although I
>>>>>>>don't imagine it will be a problem. I'd just hate for
>>
>>it
>>
>>>>>not
>>>>>
>>>>>>>to work
>>>>>>>because of a power shortage. What do you guys think?
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>On 12/6/07, Alberto Gaitán <alberto.gaitan at gmail.com>
>>>>>
>>>>>wrote:
>>>>>
>>>>>>>>Yes! I like the idea of divving up the work
>>>>>
>>>>>factory-style!
>>>>>
>>>>>>>...some folks
>>>>>>>
>>>>>>>>building cubes, and others POV thingies. And the idea
>>>>>
>>>>>for a
>>>>>
>>>>>>>>mega-LED-cube is genius enough to stop traffic for
>>
>>hours
>>
>>>>>in
>>>>>
>>>>>>>Boston!
>>>>>>>
>>>>>>>>A
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>On 12/6/07 11:33 AM, R. Mark Adams, Ph.D. wrote:
>>>>>>>>
>>>>>>>>>I think this sounds great- if we follow the 'sewing
>>>>>>>
>>>>>>>circle' approach,
>>>>>>>
>>>>>>>>>people are certain to feel like they had an enjoyable
>>>>>>>
>>>>>>>time, as well as
>>>>>>>
>>>>>>>>>(potentially) making something interesting. I would
>>>>>>>
>>>>>>>suggest that we buy
>>>>>>>
>>>>>>>>>and build at least a couple of POV kits in advance,
>>
>>so
>>
>>>>>>>people who finish
>>>>>>>
>>>>>>>>>their cubes could hook them up and get so see what
>>>>>
>>>>>they
>>>>>
>>>>>>>look like working.
>>>>>>>
>>>>>>>>> in fact, if we encourage the group to work together
>>>>>>>
>>>>>>>collectively, we
>>>>>>>
>>>>>>>>>could set it up so that folks are each working on
>>>>>
>>>>>parts
>>>>>
>>>>>>>that can all come
>>>>>>>
>>>>>>>>>together in the end to have something working.
>>>>>>>
>>>>>>>mega-LED-cube, anyone? :-)
>>>>>>>
>>>>>>>>>I am happy to volunteer to buy a couple of kits/LEDs
>>>>>
>>>>>to do
>>>>>
>>>>>>>some
>>>>>>>
>>>>>>>>>pre-building if people would like. I can also knock
>>>>>
>>>>>off
>>>>>
>>>>>>>some wooden jigs
>>>>>>>
>>>>>>>>>to aid in the LED cube construction. (I can use the
>>>>>
>>>>>robot
>>>>>
>>>>>>>I showed last
>>>>>>>
>>>>>>>>>time to make them- cool!)
>>>>>>>>>
>>>>>>>>>I also have some tool kits and soldering irons that
>>>>>>>
>>>>>>>tool-less folks can
>>>>>>>
>>>>>>>>>use at the meeting if they want.
>>>>>>>>>
>>>>>>>>>Thanks!
>>>>>>>>>Mark
>>>>>>>>>
>>>>>>>>>Gareth Branwyn wrote:
>>>>>>>>>
>>>>>>>>>>Hey Everybody,
>>>>>>>>>>
>>>>>>>>>>As I'm sure you all know, we need to step on it to
>>>>>
>>>>>get
>>>>>
>>>>>>>the LED Cube
>>>>>>>
>>>>>>>>>>workshop in gear.
>>>>>>>>>>
>>>>>>>>>>I talked to Dan Woods at the Maker Store and it's
>>
>>not
>>
>>>>>>>firm yet, but
>>>>>>>
>>>>>>>>>>it sounds like they'lll sell us the MiniPOV kits for
>>>>>
>>>>>cost
>>>>>
>>>>>>>in exchange
>>>>>>>
>>>>>>>>>>for a "Sponsored by MAKE" and a link on their
>>>>>
>>>>>website, in
>>>>>
>>>>>>>the
>>>>>>>
>>>>>>>>>>announcements, etc. The problem is that, given the
>>>>>>>
>>>>>>>season, the kits
>>>>>>>
>>>>>>>>>>are in short supply. He said supply should free up
>>>>>
>>>>>after
>>>>>
>>>>>>>Xmas, so
>>>>>>>
>>>>>>>>>>hopefully they could have them to us in early
>>>>>
>>>>>January.
>>>>>
>>>>>>>>>>Tim Slagle said that he could get the LEDs
>>>>>
>>>>>themselves.
>>>>>
>>>>>>>Katie Bechtold
>>>>>>>
>>>>>>>>>>and Mark Adams have also volunteered to help. (all
>>>>>
>>>>>copied
>>>>>
>>>>>>>in here)
>>>>>>>
>>>>>>>>>>Alberto said that he'll draft the announcement that
>>>>>>>
>>>>>>>Koshland needs to
>>>>>>>
>>>>>>>>>>see, sooner than later. I'll also help in editing
>>>>>
>>>>>that.
>>>>>
>>>>>>>>>>So, we need to figure out ASAP how we're going to
>>
>>run
>>
>>>>>>>this thing.
>>>>>>>
>>>>>>>>>>Personally, I'm not that concerned about whether the
>>>>>>>
>>>>>>>cubes are
>>>>>>>
>>>>>>>>>>finished by the end of the workshop or not. To me,
>>>>>
>>>>>these
>>>>>
>>>>>>>things are
>>>>>>>
>>>>>>>>>>more like a sewing circle than anything else, a
>>>>>
>>>>>chance to
>>>>>
>>>>>>>socialize,
>>>>>>>
>>>>>>>>>>geek out, learn a skill and a few tips from those
>>>>>
>>>>>more
>>>>>
>>>>>>>experienced,
>>>>>>>
>>>>>>>>>>etc. But others might have a different take.
>>>>>>>>>>
>>>>>>>>>>Given the "shortage" of POV kits, we may have
>>
>>trouble
>>
>>>>>>>getting a lot,
>>>>>>>
>>>>>>>>>>if say, 25 or more people each wanted a kit. One
>>>>>
>>>>>thing we
>>>>>
>>>>>>>could do is
>>>>>>>
>>>>>>>>>>also approach Lady Ada, the maker, and see if she'd
>>>>>
>>>>>give
>>>>>
>>>>>>>us a
>>>>>>>
>>>>>>>>>>discount. Even if she didn't, we could buy them full
>>>>>>>
>>>>>>>price from her
>>>>>>>
>>>>>>>>>>(at $17.50 ea) and spread out the cost over all the
>>>>>
>>>>>kits
>>>>>
>>>>>>>we offered
>>>>>>>
>>>>>>>>>>to people.
>>>>>>>>>>
>>>>>>>>>>So, we need to get a show of hands ASAP for how many
>>>>>>>
>>>>>>>people plan to
>>>>>>>
>>>>>>>>>>purchase a kit. And for one thing, we should insist
>>>>>
>>>>>that
>>>>>
>>>>>>>you have to
>>>>>>>
>>>>>>>>>>be participating in the workshop to get the kit at
>>>>>
>>>>>the
>>>>>
>>>>>>>discounted price.
>>>>>>>
>>>>>>>>>>Gareth
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>
>>>>
>
>
- --
| | "Information is light. |
| R. Mark Adams, Ph.D. | Information in itself, |
| Computational Biologist | about anything, is light." |
| rmadams at epotential.com | - Tom Stoppard |
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