Show Posts
Pages: 1 ... 331 332 [333] 334 335 ... 462
4981  Forum 2005-2010 (read only) / Development / Re: LGA-14 to DIP-14 adapter artwork on: April 23, 2010, 09:22:53 pm
Freescale has some pretty fierce recommendations for PCB layout in AN3484, including the use of VERY narrow traces (0.1mm) connecting the accelerometer pads to the main traces.  Apparently these help prevent stresses in the PCB from affecting the internal bits of the chip.

You haven't done these things, but then you're not doing the sort of machine assembly that might be causing the need for such things either.  How are your results?
4982  Forum 2005-2010 (read only) / Development / Re: can't download program via arduino with my PCB brd on: April 21, 2010, 02:38:20 am
Which version of your schematic/PCB are you working with?  The first version looks like it is missing the auto-reset capacitor, and I'm not sure it would behave properly.

Your board is also running at 8Mhz?  Are you sure you have the proper rom monitor hex file for an 8MHz system?

I would suggest that you connect to the arduino serial port with some sort of terminal emulator, and see if it responds the way the arduino bootloader would be expected to.
(notably, send "1 " and see if you get "AVR ISP")  If it doesn't immediately work, try different serial speeds...

I don't see anything obviously wrong with the schematic.  Mine has the FTDI RESET line tied to Vcc, but IIRC that shouldn't be necessary, and the results you are getting would seem to indicate that you don't have an "FTDI stuck in reset" problem.

4983  Forum 2005-2010 (read only) / Development / Re: How to move soldering pads to top layer in Eagle? on: April 19, 2010, 11:26:17 pm
Quote
the pads will always be on both sides?
There are two types of component mounting for PCBs.
There are surface-mount components whose leads attach to "SMDs" (in EAGLE-speak) or "Surface Mount Pads."  These to not include any holes, and exist on only one side of the PCB.
And then there are "through-hole components" which have a ring on both sides of the PCB (actually, on ALL layers of the PCB) with a Hole in between them that the Component lead goes Through.  The pads for these (almost) always appear on both layers.

The common exception is single-sided boards, which are implemented by only giving the PCB fab house one layer to print; in the CAD files the pads are still on both sides, but only one side is actually fabricated.
4984  Forum 2005-2010 (read only) / Development / Re: How to move soldering pads to top layer in Eagle? on: April 19, 2010, 05:10:51 pm
Quote
I just thought that it didn't make sense to have the pads on both sides...
Take a look at any professionally mad PCB and you'll see that the pads ARE on both sides.  This adds quite a bit of structural integrity (there will usually be solder on both sides too), as well as permitting signals to be routed to either side of a pin.
4985  Forum 2005-2010 (read only) / Development / Re: How to move soldering pads to top layer in Eagle? on: April 19, 2010, 10:18:15 am
Quote
how do I set the pad size in a certain layer individually for a specific part?
You can't.  I'm not sure that you should want to, but it apparently is a feature found in some other CAD packages.  If you want larger than normal "pads" in a layer, you can (at least theoretically) write a ULP that draws polygons around each pin.  For example, see pinpoly.ulp in http://tech.groups.yahoo.com/group/eaglecad/files/scr%26ulp/
4986  Forum 2005-2010 (read only) / Development / Re: Long female header pins? on: April 07, 2010, 11:32:18 pm
SSQ is the correct part (SQ = "SQuare" tail.)  Sorry for the earlier incorrect part number. :-(
4987  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...)
4988  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.
4989  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...
4990  Forum 2005-2010 (read only) / Development / Re: Arduino Mega with Accelerometer and RTC on: May 22, 2009, 02:08:22 am
Quote
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.

Quote
- 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.

Quote
- 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.

Quote
- 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...)

Quote
- 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...
4991  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...)
4992  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...
4993  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.
4994  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...
4995  Forum 2005-2010 (read only) / Development / Re: Industrial grade motor control with Arduino on: April 08, 2010, 04:19:25 pm
Quote
Quote
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...)
Pages: 1 ... 331 332 [333] 334 335 ... 462