Toner Transfer and Muriatic Acid Etchant: Making PCBs at LVL1


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.


A Project is Born


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.