Here are some things I wrote about on my old blog, These still get google hits, so they're preserved here for posterity!

A Tiny Balloon Computer

November 11, 2011

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

Makerbot Sumbot

July 7, 2011

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

Toner Transfer and Muriatic Acid Etchant: Making PCBs at LVL1

April 4, 2011

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

A Project is Born

February 2, 2011

Schematic of a Wireless Garden MonitorI 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

Meat and Networking

January 1, 2011

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.

Read More