Eventually, hand soldering surface mount components becomes a pain, especially if you’re doing small manufacturing runs. It’s much easier to work with solder paste and a hotplate.  Joints are higher quality, and you can manufacture more boards at once.  If it was good enough to get Sparkfun started, it’s certainly good enough for us! Working with solder paste does require a stencil, though.  The stencil contains precisely sized holes which allow solder paste to be precision applied to the metal pads on your PCB.  There are many companies which will provide cheap and high quality stencils, but if you have access to a laser cutter, there’s no reason you can’t do this yourself.

There are a lot of guides out there for creating SVG stencils from Eagle, so I’ll be covering KiCad in this tutorial.  Additionally, the laser cutter I have access to at the LVL1 Hackerspace is a Full Spectrum laser which can cut directly from Inkscape, so I’ll be basing this tutorial on Inkscape.

Step 1

Generate gerbers from your completely routed KiCad PCB project.  There are a lot of good guides out there for getting to this point in KiCad.

http://reprap.org/wiki/KiCad

http://code.google.com/p/opendous/wiki/KiCADTutorialCreatingGerberFiles

and a collection of resources here: http://meatandnetworking.com/w/Kicad_Resources

Step 2

Open your PCB in a program like Gerbv.  Any gerber viewer capable of outputting to SVG is alright for this, but I like gerbv the best.  You’ll want to open the solder paste layer, which KiCad names by default to something like “pcbFileName-SoldP_Front.gtp”.

Export to SVG, put the file anywhere you like. In Linux, you have to manually add the SVG file extension.

Step 3

Open the file in Inkscape.

Ungroup the objects by right-clicking on a pad or line and selecting “Ungroup.”

Open the “Fill and Stroke” menu.

Clear the “Fill”.

Turn on “Stroke” and set it to a color that your laser cutter likes.

Our full spectrum laser will try to cut the inside and the outside of the stroke if it’s too thick.  .1mm is thin enough that our laser cutter software will only cut the outside of the stroke.

Step 4

Before proceeding, you can delete the board outline, since it’s unnecessary.

Select all the objects, and open the “Transform” menu under “Object.”  Under the “Scale” tab, MAKE SURE that “Apply to each object seperately” is CHECKED.  This maintains the centroids of all your pads.  You’ll have to play around a little bit to get this value just right. Decreasing the size of the features is necessary due to the thickness of the stencil material.  The thicker the material, the more you’ll need to reduce the size of each feature.  For overhead transparency plastic, 90% is just about right.

Now you’ve got a finished stencil SVG, suitable for lasering.  In a future post, I’ll show off how to soldering using paste and a hotplate.

This list will be kept up to date on the wiki: http://meatandnetworking.com/w/Kicad_Resources

KiCad is an Electronic Design tool, similar to EagleCAD. KiCad is free, open source software, and runs on OSX, Linux and Windows. KiCad is unrestricted. All features may be used for hobbyist or commercial works.

Here are some features of KiCad that might appeal to the hobbyist:

Getting Started

• Kicad Project Homepage
  KiCad can be downloaded here. KiCad support on OSX is alright, but not as good as the other platforms.

• kicad-testing-daily
  For Ubuntu users: Adam Wolf maintains a launchpad PPA for the KiCad daily build. This build is generally stable, and months ahead of the “official” release.

• How to build KiCad from source
  Wayne and Layne have a great article on how to build KiCad from source (on Ubuntu).

Basic Tutorials

• Curious Inventor KiCad Guides
  These guides are very comprehensive, and will get you up and running in no time at all. Unfortunately, they’re a little out of date. For example, they still refer to KiCad as having no “undo” functionality, which it now does.

• Teho Labs Kicad Tutorial
  Brian from Teho Labs wrote this great tutorial

• WikiBooks
  This isn’t the best tutorial in the world, but it’s got a great, thorough FAQ.

• Dr. Johnathan Hill’s Kicad Tutorials
  Dr. Hill takes readers through an example project, which is a great way to get a good understanding of the workflow of KiCad.

• KicadHowto.org
  This is the new tutorial on the block. It’s not very well organized, but the information contained therein is very good.

• TransTronics Wiki
  Again, poorly organized, but there’s a lot of good info about general KiCad use here. Some parts are also a bit out of date.

KiCad Libraries

EagleCad users are familiar with having large parts libraries available instantly. With companies like Adafruit, Sparkfun and DangerousPrototypes publishing high-quality Eagle libraries, it can be tough to transition. These resources should help you overcome that hump.

• KiCadLib.org
  A highly respectable collection of library components.

• Open Source Hardware Engineering Community Library
  Here you’ll find all the default component libraries that come with Eagle converted for use in KiCad. Not all of them are 100%, but it’s a great boost.

• QuickLibGen
  When you have to make your own part, this can really speed up the process. Provide some basic info, and download your schematic symbol.

• Footprint Builder
  A Java program for quickly creating certain types of land patterns for KiCad components.

• Creating and Modifying Symbols for KiCad
  This PDF does a good job of covering some of the more fiddly parts of creating and modifying symbols using the build-in editor.

Another PCB design gets shipped off to China for manufacture!

This is a tiny balloon computer.  Without battery or GPS, it weighs less than 40 grams.  It can transmit RTTY or CW at 25 mW on the ham 2M and 70cm bands, and will last up to 16 hours on a single AA.

This board will be Arduino compatible, and the primary goal will be to support White Star‘s superpressure balloon experiments.  A superpressure balloon maintains some pressurization above ambient in order to maintain altitude.  In order to figure out how to design the balloon envelopes, and to verify our math, we need to know what’s going on inside the balloon.  It’s difficult to pierce the balloon without generating leaks. The ideal solution is to place a second balloon computer inside.  Both will transmit pressure to the ground, and we’ll be able to compare pressure inside the balloon to ambient pressure for model verification.  The pressure sensor can sense a change as small as 4×10-4 PSI, so this should work.

This is my first attempt at real RF design.  Fortunately, operating within the ham radio bands means I don’t have to worry too much about spurious transmissions or leaky harmonics.

» Read more…

LVL1 has a small rivalry with a few of the regional hackerspaces.  Back in October 2010, when we were but a fledgling space, we hosted a Sumo Bot tournament.  Hive13 and Bloominglabs came by, and we kicked their butts.  Hive13 held the rematch a few months ago, and I started work on my SumoBot.  Unfortunately, I didn’t finish in time, but the effort itself is worthwhile, and my bot will live to see the next match.

Sumobots are robots which seek to push each other out of a small ring.  The ring is black, with a white boundary circle.  Two robots enter, one robot leaves. Our competitions use the Mini-Sumo class of rules, allowing for a Sumobot which can fit inside a 10cm by 10cm rectangular tube, weighing under 500 grams.  I decided to print my SumoBot on our makerbot.

» Read more…

LVL1 is great.  A place for creative and motivated people to get together and goad each-other into doing more creative things.  It’s also a great gathering place for tools, as well as knowledge.  A few months ago, the spoiled electrical engineer that I am, I never would have considered making my own PCBs.  Any project worth taking off the breadboard was worth sending to China to get made “right.”

Of course, there isn’t always time and money to send something to China.  Today’s installment is the Sumo-bot board I’m trying to put together for the Hive13 sumobot competition.  Unfortunately, it doesn’t look like poor Snoopy bot will make it to the ring, but the board making process itself is worth talking about.

Laying out a PCB using software like Eagle is beyond the scope of this post.  If you can follow the appropriate Sparkfun Tutorial, it’s pretty easy to pick up.  Something to note:  for single sided home-made PCBs, put all traces and surface mount components on the BOTTOM layer.  Put any necessary jumpers on the top layer.  When you’re ready to print, just turn off all the layers you don’t want turned into copper.

» Read more…

I decided to take a personal day today, and I sat down and knocked out the schematic for a project I’ve wanted to work on for a very long time.

This is a  wireless mesh-networking garden monitor.  It’s configured to monitor soil moisture, soil temperature, ground temperature, as well as air temperature and humidity.

This is interesting information to know, as it provides significant insight into microclimates on a given plot.  It can also reveal information about how well your soil retains moisture, etc. etc.

It will be powered by solar cells, which will opportunistically charge a LiPo battery.  The wireless communication is provided by an Xbee, which is mounted on the back.  The microcontroller is an Atmega 328p.  A Microchip MCP73833 charges the LiPo whenever the solar voltage is adequate, and a Micrel 5205 regulates this voltage.  The device is configured for reprogrammability over the Xbee link.  I’ll probably also add an FTDI cable port for easy debugging early in the development process.

This portion of the board will sit near the ground.  There is a below ground and above-ground portion, as well.  The above ground portion contains a humidity sensor, temperature sensor, and 1W solar cell.  The below ground portion will contain a soil moisture sensor and temperature sensor.  I’m going to cover the whole thing in conformal coating, and see how long it lasts in the elements.

» Read more…

I am Brad, a twenty-something electrical engineer, tinkerer, balloonist, and gadfly.

Why Meat and Networking?  I’ve owned this domain since 2007, when I moved in to a house with three friends.  In the months leading up to moving  in together, every conversation about the house ended on the topic of  either meat or networking, so I bought this domain, intending it to be a house blog, as an impulse.  I have long since moved out, but Meat and Networking accurately describe many of the communal activities of that household.