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4966  Forum 2005-2010 (read only) / Development / Re: Long female header pins? on: May 01, 2009, 12:17:54 am
[repeating an earlier post]

It's a "Tail option" on Samtec's SSW line of connectors (for example; I imaging other manufacturers do similar things.)

http://www.samtec.com/ftppub/pdf/SSW_TH.PDF

Samtec is a great manufacturer; been in business forever, generous with samples, generally helpful and communicative, and available through digikey.  (I don't know if you can get ALL samtec parts through digikey, though...)
4967  Forum 2005-2010 (read only) / Development / Re: Eagle question on: April 10, 2010, 03:10:06 am
Better to change your "grid" settings until it works for you than to move all the components around...  The original Arduino is just "off grid"; the board partially because it's very common to move components to finer positions to tighten things up, and partially "other";  I've never quite figured out why the schematic is off-grid...

There are "ULPs" that will put the components on-grid for you
"run cmd-snap-board"  for the board (which will make quite a mess!) and
"run snap-on-grid-sch" for the schematic, which seems to work pretty well.
4968  Forum 2005-2010 (read only) / Development / Re: Arduino Mega with Accelerometer and RTC on: May 24, 2009, 05:16:13 am
Yes, this latest version looks much better...
4969  Forum 2005-2010 (read only) / Development / Re: Arduino Mega with Accelerometer and RTC on: May 22, 2009, 02:08:22 am
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Q: diagnal groundplane on top layer?
A: that was what the reference file came with ... Should I change it?
Hmm.  The copy I downloaded has a rectangular groundplane on top.  You probably accidentally deleted the bottom right corner when adding the battery; it's easy to miss doing this when the groundplane isn't filled in.

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- horizontal lines: I guess I didnt' realize that was important (slap, don't be sloppy), I'll clean that up more (finer Alt setting).
It's not important on its own, but it probably contributes to some of the clearance errors.

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- I was under the impression (wrong?) that the ISP header also breaks out the necessary lines for external SPI bus connections, so I didn't bother.
No, you're correct.  I forgot about those, and didn't see it.  I never liked connecting shields via signals on the ICSP connector, but it's probably sufficient.

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- Westfw, you reminded me that it probably should have a cap next to the SCA3000 on the power line. The SCA is miniscule amperage, suitable for the 3.3 line. Should it have an electrolytic and a ceramic like the Sparkfun breakout board? I have no idea how well conditioned the 3.3v supply is.
Good question.  I don't know.  Sensitive analog component; I'd put as many caps near it as will easily fit on the board, and maybe an inductor or resistor connecting them to the main supply as well.

Can you fit it out for possible population with cheaper accelerometers (ie dual footprints)?  Everyone with micromachining capabilities is chasing the "shake your iPod" market with cheap three-axis accelerometers (ie MMA7455L from Freescale - under $4 in ones...)

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- all the little warnings were a little confusing and I couldn't find any actual problems when I checked the circuit board, but that just means I don't know what I'm doing!
Yes, you need to look at them more carefully.  The design rules are already set to "typical" limits of PCB manufacturers, so anything that's closer than the 8mil clearance really ought to be cleaned up.  "dimension" is less important.  And I saw at least two real errors where traces carrying different signals actually collide (near (73,17) and (78,40))  I'm a big fan of making things "easy" for the PCB manufacturer...
4970  Forum 2005-2010 (read only) / Development / Re: Arduino Mega with Accelerometer and RTC on: May 21, 2009, 06:01:09 pm
The top-layer ground plane cuts diagonally across the board.  Is that what you meant to do?

Many of the "horizontal" traces in the upper right top layer are not very horizontal.

Running a DRC check turns up many clearance errors and several "overlap" errors that look like they might be real problems (and some that aren't.)

SPI is multi-device capable on MISO, MOSI, and SCK.  You might want to run those pins to connectors even though you're using them for the SCA3000.

(these are generic comments; I don't know anything abou the SCA3000 in order to say whether you defined the part right, or have sufficient 3V/5V conversion stuff, etc...)
4971  Forum 2005-2010 (read only) / Development / Re: Bare bones that fits shield pin layout? on: January 15, 2010, 11:29:11 am
Here's an outline comparison.  The V.3 board adds another 10mm in the X direction and a bit in the Y direction, but it also moves the ICSP connector to the right place, adds auto-reset, the two extra pins on the power connect area, and some useful option jumpers and has fewer signal jumpers.


I'll check on the "publishable" status of the .93 version...
4972  Forum 2005-2010 (read only) / Development / Re: Bare bones that fits shield pin layout? on: January 15, 2010, 05:51:26 am
The Serial Single Sided Arduino I posted does NOT fit in the standard footprint area; it's about 1cm bigger in each direction.

The "ShieldDuino" is not a full arduino, and isn't single sided.
4973  Forum 2005-2010 (read only) / Development / Re: Bare bones that fits shield pin layout? on: January 15, 2010, 02:24:46 am
I think you underestimate the "difficulty" of moving connectors around on a PCB.  You might think that "gee, the Really Bare Bones Arduino fits on that 76mm*18mm PCB, if all you're doing is adding connectors in the right places, it ought to be trivial to fit it in the 70x55mm space of a "real" arduino."  But the RBBB uses a "convenient" pinout, and "translating" pinouts is one of the more difficult and space-consuming things to do on a PCB, especially if its single sided...
4974  Forum 2005-2010 (read only) / Development / Re: Industrial grade motor control with Arduino on: April 08, 2010, 04:19:25 pm
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How much would you think would be a good price for such a device?
I don't think your price is outlandish
I agree, mostly considering what "name brand" vendors charge for "digital servos" whose capabilities are much less (as far as I know.)  $60 is pretty "middle ground."  You probably should include more information about the servo motor and mechanics, though; that seems to matter to people...

OTOH, your price is higher than I'd pay for something to just play around with.  Unless I have a particular application that needs the added capabilities, I'll probably be buying the cheap <$10 servos from China (so far, I've mostly bought REALLY cheap micro-servos...)
4975  Forum 2005-2010 (read only) / Development / Re: Industrial grade motor control with Arduino on: April 07, 2010, 02:18:11 pm
Looks neat.

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- Control loop at 1KHz.(Rather than  the usual 50 or 100 or 200 Hz)
So the actual demo moves the servo pretty slowly (average for a servo?  Limited by the servo motor and gear train, probably?)  (looks like about 60rpm (one rps))  Have you done any experiments to see how fast it could work?
4976  Forum 2005-2010 (read only) / Development / Re: Half of an SN74HCT08N? on: March 23, 2010, 12:37:25 am
even tinier:  http://focus.ti.com/docs/prod/folders/print/sn74lvc2g17.html
4977  Forum 2005-2010 (read only) / Development / Re: Half of an SN74HCT08N? on: March 23, 2010, 12:31:46 am
http://focus.ti.com/docs/prod/folders/print/sn74lvc2g241.html ?
Other vendors have similar "tiny logic" things these days; one or two gates in itty bitty packages.
4978  Forum 2005-2010 (read only) / Development / Re: Integrated Arduino  Zigbee with new ATmega128RFA1 on: January 09, 2010, 08:31:33 pm
You might want to wait a bit till you can actually buy such chips.   In an apparently new strategy, Atmel's 12/09 announcement doesn't even include a guess at to availability of the chip (nor could I find anything on their web pages.)  I guess that in theory, this is a less ambitious product than then Xmegas, and could do much better, but...

I'm not sure what the implications of building an RF device from chip level is.   One of the advantages of the "module" approach taken by Zigbee and Bluetooth Arduinos is that Radio certification issues are handed off to someone else...
4979  Forum 2005-2010 (read only) / Development / Re: Crystal question on: April 04, 2010, 03:22:35 pm
The only mystery left is that 22pF is approximately the correct capacitance for these, while 22 uF is impossibly too large a cap.   Did you reverse which ones did and didn't work?
4980  Forum 2005-2010 (read only) / Development / Re: Crystal question on: April 04, 2010, 12:14:09 am
http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1824&appnote=en011973
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