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4921  Forum 2005-2010 (read only) / Development / Re: real name for stacking headers? on: August 14, 2010, 04:36:20 pm
Samtec just calls them "through-hole .025in sq post socket with square tails"  (and you order with a particular "long" tail length.)
4922  Forum 2005-2010 (read only) / Development / Re: Schematic Software on: September 06, 2010, 05:55:58 pm

If you really feel like doing that sort of thing, why not contribute to one of the existing open-source projects (Fritzing, geda, kicad) ?
4923  Forum 2005-2010 (read only) / Development / Re: Part# for: 16 MHz crystal oscillator on: November 23, 2007, 05:14:21 pm
I prefer ceramic resonators with built-in caps. :-)
4924  Forum 2005-2010 (read only) / Development / Re: Part# for: 16 MHz crystal oscillator on: November 22, 2007, 11:55:18 pm
Actually, I think the caps appear in series WRT the relevant oscillation circuit...

You may have other 16Mhz crystals that need require a different load capacitance
My understanding of crystal/cap selection goes like this: "picking a correct crystal and capacitors for a particular micro is more complicated than most people think.  You can't just lay down a "generic" crystal and a couple of 22pF caps and expect everything to operating within the manufacturers specs.  You have to  know things about the particular crystal and its load capacitance, along with the inherent capacitance of the circuitry in the microcontroller and board traces, and probably you should pay attention to drive  levels too.   However, the typical consequences of doing it "not quite right" are either non-oscillation, or operating at a frequency slightly off specification.  Assuming the microcontroller operates at all (which means the crystal IS oscillating), it is probably operating close enough to the desired frequency that few applications will notice the difference.  So in theory, you can't just use a "generic" crystal circuit, but in practice, it almost always works anyway."

Microchip is supposed to have some good app notes on crystal selection and oscillator design.  I found:
 AN826 - Crystal Oscillator Basics and Crystal Selection for rfPIC™ and PICmicro® Devices
and AN849 - Basic PICmicro® Oscillator Design
Each goes into some detail on how the oscillator works, how you should pick caps and crystals, and how to tell whether it's working right.
4925  Forum 2005-2010 (read only) / Development / Re: Part# for: 16 MHz crystal oscillator on: November 15, 2007, 07:30:42 pm
Unfortunately, there are several types of "generic crystal."  The consequences of using the wrong type are usually small, but detectable, and an actual part number would be a good idea.
(we once ("in the dawn of the internet") shipped some products with a series resonant crystal instead of the correct parallel resonant crystal on an Ethernet controller chip.  It generally worked fine, but a customer was able to detect the out-of-spec state.  Very embarrassing.)
4926  Forum 2005-2010 (read only) / Development / Re: AVR board design ---- using eagle cadsoft 5.8 on: August 20, 2010, 09:36:37 am
Look in the con-subd library that comes with eagle.  Should be "M09x"  (most serial designs have put a female db9 on the board, BTW.)  See the single-sided serial PCB designs that are published on the hardware page.
4927  Forum 2005-2010 (read only) / Development / Re: Arduino Ethernet Shield on: April 02, 2008, 12:15:09 am
Lady Ada's board uses the Lantronix X-port, which is different from the wiznet chip.  In theory, the wiznet chips and modules are more general purpose, cheaper, and harder to talk to.  Looks like modules are down around $22 each here:
4928  Forum 2005-2010 (read only) / Development / Re: Ethernet shield with Power-over-Ethernet support on: August 20, 2010, 12:35:12 am
The signalling system isn't really particularly hard to implement for a commercial device
I dunno.  The "Powered Device" side is significantly more complex and more expensive than an AC plug-in switching power supply ("wall wart.")  On the ethernet switch side, a high density switch ends up needing a pretty massive power supply to handle all the devices that MIGHT request power, which is not good for efficiency (it seems like PoE specs got finalized just before everyone started to get careful about "green" electronics with low standby power.) (And the high performance switches were power hungry beasts even before they had to power an office full of phones.)  Even an 8 port home hub would theoretically need something like a 160W power supply (instead of the usual 10 to 20W) if it wanted to have a hope of powering the theoretical limit of connected devices.  The modules you can buy all seem to be aimed at the higher power devices (IP phones.)  And the most common powered device seems to be one of those IP phones, which is usually sitting next to a normal power outlet anyway (though of course there is a long tradition of having phones be on a separate power system.)
I don't mind the 48V, but I find the whole thing rather ... inelegant.  Grr.  Perhaps I'll change my mind when the cheap 5V@500mA (USB equiv) module shows up.  But I'm not holding my breath!
4929  Forum 2005-2010 (read only) / Development / Re: Ethernet shield with Power-over-Ethernet support on: August 19, 2010, 01:59:32 am
PoE is going to be a real mess with everyone throwing random amounts of voltage on the spare wires (which aren't even spare at for GE.)  I wish the official spec wasn't so complicated :-(
4930  Forum 2005-2010 (read only) / Development / Re: Possible to build with Arduino? on: June 02, 2010, 04:21:05 am
You know that these days you can buy "one port ethernet to serial gateways" for about the price of Ardunio+ethernet shield.  Some of them are production plug-and-go devices, some must be programmed by the user but come equipped with appropriate libraries, and some are hybrids.  There are both modules for embedding in other circuitry, and boxed devices...






And of course you have you usual multiport terminal server boxes from the older vendors, usually starting at 8 or 16 serial ports.  I don't think that most of these have kept up with the small device servers; their price per port tends to be alarmingly high (especially our poor cisco boxes that we try to slot into that service these days.)  There are also open source terminal server projects aimed at turning old PCs into multiport terminal servers (supporting all manner of odd and rare async cards...)

4931  Forum 2005-2010 (read only) / Development / Re: Induino - Low Cost Arduino USB Clone on: March 09, 2010, 01:31:19 am
So is there somewhere that a typical hobbyist can get single-sided PCBs made for significantly less than double-sided PCBs?  With most of the low-quantity (prototype) houses it seems you only save about 20% dropping down to single sided (using Olimex as an example.)
4932  Forum 2005-2010 (read only) / Development / Re: Arduino with ATmegA644 on: July 24, 2010, 05:12:55 pm
4933  Forum 2005-2010 (read only) / Development / Re: Drill size and stand-offs on: August 02, 2010, 03:47:25 pm
Um, no caps for the crystal?

I agree with other people that the clearances should be bigger.
Use the "DRC" button and fiddle with the assorted tabs.
(see  (though the actual values used there are aimed at home-etching, the principles remain the same.)

Also you should probably change the autorouting grid.  It should be an even factor of both the placement grid and the smallest component pin spacing.  The eagle autorouter is pretty sucky...

4934  Forum 2005-2010 (read only) / Development / Re: Drill size and stand-offs on: July 31, 2010, 04:01:55 am
When you export your EAGLE project to an actual CNC drill file, it will be using a list of the drills that are (supposed to be) actually available (the "rack".)  Or the board shop will do the same if they accept EAGLE files.  EAGLE then picks the nearest actual drill, and complains if it is not within some tolerance (that you also specify in the CAM dialog.)
For example, if I run a "launchPad-like" board with a drill set that only includes 1/32, 1/16, 1/8, and 1/4 inch drills, I get complaints:

Generated by EAGLE CAM Processor 5.7.0

Drill Station Info File: /Users/billw/Documents/EagleProjects/--CCAM-Export/Launchpad-runtime-ss.dri

 Date              : 7/31/10 1:58 AM
 Drills            : /Users/billw/Documents/EagleProjects/cam/foo-test.drl
 Device            : Excellon drill station

Parameter settings:

 Tolerance Drill + :  2.50 %
 Tolerance Drill - :  2.50 %
 Rotate            : no
 Mirror            : no
 Optimize          : yes
 Auto fit          : yes
 OffsetX           : 0inch
 OffsetY           : 0inch
 Layers            : Drills Holes

Drill File Info:

 Data Mode         : Absolute
 Units             : 1/10000 Inch

Drill Tolerances:

 -- Requested --  -- Used Drill --

 Size       used  Code  Size

 0.0315inch     7  T10   0.0310inch

Missing Drills:

 -- Requested --

 Size       used

 0.0400inch    10
 0.0360inch    20
 0.0320inch    44
 0.0394inch     4

Drills used:

 Code  Size       used

 T10   0.0310inch     7

Total number of drills: 7

4935  Forum 2005-2010 (read only) / Development / Re: Drill size and stand-offs on: July 30, 2010, 06:18:46 pm
This is probably a clearance hole for #4 screws.
I always assumed that the holes were designed for M3 (metric, 3mm 9?)) screws.  (The hole is 3.2mm)  They weren't designed in the US, you know...
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