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Topics - bearmos

General discussion / shipping PCB's internationally from USA
I'm trying to send a moderately sized PCB (~3" x 4")from the USA to Thailand. 

I was hoping to use a similar method as outlined in the DP wiki.  After sending the wife to the post office she came back to inform me that they were going to treat it as a parcel, require different packaging and charge > $7 to ship it (and require a customs declaration form to be filled out)!

Has anyone shipped PCB's from the US to another country, any tips?

It seems to me that an envelop with a PCB should qualify as a "rigid object"

The total price for a 1.1 oz envelop with a rigid object should only be ~$2.

Can I assume the people at my local post office are simply ignorant (apparently it took two of them to come up with the answer they did)?  Can I just add the proper amount of postage to the envelop and drop it in the mail (without the customs declaration)?

Any advice would be much appreciated!
General discussion / Re: Video and Audio Chips
wow...quite an undertaking.  i have no design experience with SBC's (only programming for them every once in a while) - what CPU are you basing it on?
General discussion / Cheap LCD's
I came across some really inexpensive LCD displays pulled from ereaders/tablets.  Neither of these would have a trivial implementation for the uninitiated, but I thought someone might find some use for them, especially for the price.  Here' some information I pulled together on them.

$5 Kindle Fire Color 7" 1024x600 LCD (pn LD070WS2)
* mating connector:JAE AA01B-S030VA1 (0.5mm pitch)
* configuration over SPI, data over 4 channel LVDS
* Datasheet:[attachment=2]

$3 Kindle? Greyscale 6" 800x600 bi-stable LCD (pnED060SC4)
* mating connector: JST 39FXL-RSM1-S-H-TB (0.3mm pitch) [attachment=0]
* parallel 3.3V logic levels, requires +22V/-20V and +/-15V supplies
* Datasheet:[attachment=1]
Project development, ideas, and suggestions / Re: ESR Meter
MickM, thanks for documenting this so well. 

I think I remember seeing you reference to the original one a while back, but there's definitely enough information here to replicate this easily now.  This should definitely come in handy for those pesky electrolytics on the broken SMPS i have laying around ;-)  It looks like it should probably come in under $15 after all the odds and ends are purchased (analog current meter, HV caps, plus, etc), so it should pay for itself immediately since I won't be blindly replacing all the caps on the board.
Project logs / CNC Stepper Controller
Here's a concept for a CNC stepper controller.  Actual step/direction path generation is performed by a PC running EMC2 (or equivalent) and is passed to this board over the parallel port.  I wrote a full post describing some of the details of the design.

This board is mainly designed to be inexpensive, have lots of indicators for showing what's going on (making troubleshooting a bit easier).  It includes integrated driver chips (not modules that need to be purchased at $15 ea), which should also help out with heat dissipation. 

The only (relatively) novel thing about this design is that it includes some circuitry to automatically reduce the current (~1/3 of "active" current) to the stepper motors after they're inactive for a period of time (probably around 1 sec).  A small PIC, an analog mux, and a resistor network are included to take care of this task.

Input power is fairly flexible, an ATX header is included so the whole thing can be powered from a computer power supply (although the 12V won't drive steppers super-fast).  Secondary inputs for 5V (logic) and a higher motor voltage (up to 30V I think).  On-board logic can also be powered from an included LDO and only use the motor voltage input (hopefully the LDO doesn't overheat - if it does, that's what the external 5V connection is for ;-)).

If the board form-factor looks familiar, that's because it's based on a DP10080.  I had started the board out with the max dimensions of eagle, towards the end I rounded the corners and nudged mounting holes a bit to get it into the "standard" form factor.

Rendering was done with Eagleup and Kerkythea, following the excellent guides on the DP wiki.  All additional models that were required are in the DP SVN.

Design Review
I'd love to hear some feedback before I send it off to fab.  Unfrotunately, A4982's in QFN's have fallen off the face of the earth until early 2013 - so I'm either going to have to wait on them or redesign for the TSSOP version of the driver. . .

* A jpeg of the SCH that's too small to be useful: [attachment=1]
* SCH PDF: [attachment=0]
* PCB screenshot: [attachment=2]
* A sketchup model (current in Twilight Robotics SVN)
NOTE: This sketchup model can't be added, the skp extension isn't allowed and max file size is 1MB.

A [s:]up-to-date[/s:] bleeding edge schematic/board can be found in the trunk of StepDriveInterface.

This version has been tagged revA.
Project development, ideas, and suggestions / wiki extensions and suggestions
Ian et al,

Some humble suggested extensions for the wiki (exclusively based on personal tastes ;-))

* msupload

This extension makes it possible to drag and drop images without leaving the page you're editing.  I can't stress enough how fast this makes editing image-heavy pages.  Groups of images can all be dragged in at once and uploaded in one click (while editing the rest of the page).  Unfortunately, this only seems to work well with 1.18.

* CategoryTree

Creates an interactive tree.  I like to put these at the tops of all pages that are within a category - I find it really helps with navigation and finding related pages: example
General discussion / Free Cortex M4 Seminars - free food, free discovery board
Just got notice of some free seminars for the STM32F3 MCU's hosted by Nu Horizons - these are what's on the popular "discovery" boards.  These seminars are free and have free food, a free discovery board, and more sales pitches than you can shake a stick at. . .

Registration Site

In the past, some people found these useful, so I figured I'd pass this one along too.

Montrea l11/7/2012
Toronto 11/8/2012
Orange County, CA 11/13/2012
Santa Clara, CA 11/14/2012
San Diego, CA 11/15/2012
Indianapolis, IN 11/15/2012
Vancouver 11/28/2012
Dallas, TX 11/28/2012
Seattle, WA 11/29/2012
North Carolina 12/4/2012
Minneapolis, MN 12/5/2012
Orlando, FL 12/6/2012
Chicago, IL 12/11/2012
Boston, MA 12/11/2012
Milwaukee, WI 12/13/2012
Pittsburg, PA 12/13/2012

Event Details

This seminar will include technical detail on the STM32 F3 Cortex™-M4 core, system architecture, and advanced analog and digital peripherals featured in the STM32 F3 series.

Demonstrations will include how to start, develop and debug a project, develop and debug a project using the simple to use firmware libraries and low cost development tools and kits.

Seminar Agenda:

8:30 - 9:00 Registration and Continental Breakfast

9:00 - 12:00 Introduction to the STM32 F3 Series
Features of the Cortex™-M4 core
System architecture
Connectivity interfaces
Advanced digital peripherals
Advanced analog peripherals

12:00 - 1:00 Lunch Served

1:00 - 2:30 Demonstration of STM32 F3:
Development and programming tools
Evaluation and development kits
Firmware libraries
Project logs / High Current Voltage Selection
On a few projects, I've found myself needing to select between different voltages.  Normally, for logic supplies, I'll just include a simple 0.1" header and use "standard" jumpers.  But, with some higher current projects coming up, these standard jumpers just aren't going to cut it.

I compiled a list of some different (inexpensive) options for providing solder-less jumper selection for currents in excess of 15A.  Most are less than $0.25 per pole.

Maybe someone else might find this useful - it took me a little while to find exactly what I was looking for.  Keep in mind, I haven't implemented any of this yet - it's just in the idea stage - I'm curious to hear what solutions you guys have come up with for similar problems.

Here's the writeup: http://
General discussion / microchip promotion - PIC24F microstick for $9.99
If you're interested in the PIC24F series (that DP uses quite readily) - MC is running a promotion where you can get a PIC24F microstick for $9.99 (excluding taxes and shipping) if you place an order today or tomorrow (6/29/12).  It looks like a decent little board with a programmer/debugger built in - it also has some unpopulated headers that look like they'd be breadboard compatible.  Here's the normal product page.  As well as the datasheet.
General discussion / eagle - pasting pre-routed snippets
In professional ECAD tools, there's a notion of "channels" in a design.  Basically, identical circuitry that can be routed and then copied multiple times.  I've been trying to figure out how to do this (easily) in eagle, but have come up relatively empty handed.  The cadsoft forum makes mention of future improvements that enable this, but it doesn't seem that they apply to the free version.

Basically, I'd like to take this (partially) prerouted glob of circuitry and paste it (maintaining routing) a few times.

By doing a "normal" copy and paste on the schematic, you just get the components in the PCB.  After rearrangement, you wind up with this, which doesn't include any of the routing:

Thoughts and Current Work-arounds
Since eagle refuses to back-annotate copy and paste from the board, copying here isn't possible without loosing sync with the schematic.  In a way, this is vaguely similar to panelizing, but that's accomplished by copying the names and values to a text only layer, which "breaks" the schematic.

There is an old thread in the sparkfun forum which has a work-around that accomplishes what I'm looking for, but it requires that every net be renamed, which is pretty cumbersome.

The best bet for pasting I found was a paste to file command, but this doesn't seem to be supported in the free version since it pastes onto a new schematic sheet.

Final Plea ;-)
Does anyone have any suggestions?  Is this something KiCad can do?
General discussion / Free Seminar - STM32 (ARM Cortex-M0)
ST Micro is doing free Seminars in North America for their STM32 F0 MCU"s.  The seminar is free and you get an STM32 F0 Discovery Kit if you attend.

I thought this might be of interest. .  . free food and a free hardware ;-)

Seminar Agenda:

8:30 - 9:00
Registration and Continental Breakfast

9:00 - 12:00
Introduction to the STM32 F0 Series
Features of the Cortex™-M0 core
System architecture
Connectivity interfaces
Advanced digital peripherals
Advanced analog peripherals

12:00 - 1:00
Lunch Served

1:00 - 2:30
Demonstration of STM32 F0:
Development and programming Tools
Evaluation and development kits
Firmware libraries

Location   Date
Vancouver   5/16/2012
Seattle   5/17/2012
Santa Clara   5/22/2012
Cleveland   5/22/2012
Dallas   5/29/2012
Montreal    5/29/2012
Toronto   5/31/2012
Chicago   6/5/2012
Atlanta   6/5/2012
Minneapolis   6/7/2012
Orlando   6/7/2012
Orange County   6/12/2012
San Diego   6/14/2012
Boston   6/19/2012
Philadelphia   6/21/2012
Phoenix   6/28/2012

For more info and to register:
General discussion / playterm - web embedded terminal playback
I just ran across an interesting terminal player - playterm - it will efficiently playback a terminal session - letting the user copy text from it.  It's essentially the same as taking a video of a terminal session in real time - but with the advantage that the viewer can copy text from the playback.

Here's an example showing some options for the 'cat' command: http://

The only part that stinks is that it appears to be a "service" only type website - so you'll need to upload your .tty to playterm and then link to them.

At any rate, it seems like it might be a useful way of recording terminal interactions and sharing them.
Project logs / DIY plated through holes
I just finished writing up some of the details on DIY plated through holes.  This is what the simple constant current source was designed for.  This process was slightly adapted from Think and Tinker - a really great site for DIY PCB fab.  The overall process is:
1.  Drill holes in the PCB
2.  Coat the holes with a mixture of water-proof ink and finely powdered graphite
3.  Cure the ink so it doesn't rub off
4.  Dunk the PCB in the electroplating tank, apply current, and let chemistry do the rest of the work.

Here are the pages of interest:
- electroplating (part 1)
- electroplating (part 2)
- electroplating (part 3)
- electroplating (part 4)

Overall, the process is a lot simpler than I expected.  Here are some pictures for a quick overview:
The bath ingredients. ..notice nearly every chemical there has a pretty serious warning on it. . .please, take these seriously. . .:

Slopping conductive ink (all over the PCB to "activate" the through holes:

The same board, after getting the top layer of ink carefully removed (for the most part):

Plating in progress, using the simple constant current source  previously made:

And some plated through holes:

It should be noted that this is something that needs to be done *before* traces are etched into the PCB because the electroplating relies on current passing through the work-piece to deposit the copper ions onto the PCB.  If the board is already etched, anything not touching the cathode clip won't plate properly.  If you'd like to do PTH's with an etched board, you'll need to pattern plate tin solder or bright tin first (see think and tinker for details).  This tin plating will also coat the insides of the PTH's so the copper doesn't disappear, since the tin acts as an etch resist.

The copper doesn't come out all that "bright" (probably because the bath lacks brighteners and anode bags).  But, this sure beats soldering individual wires through vias, and I can put them under IC's now without any hassle - all this while still getting my board done the same night!