Saturday, October 2, 2010

Arduino Mega 2560 Operational!

I ported our temp / humidity (and not quite right barometric pressure) project over to the Mega 2560 a few minutes ago. So many more I/O pins. I love it! Will continue working on time date functions, and getting the barometric pressure reading sorted out. Once I get the BP working, I have to figure out code that will take comparative readings, and show rising or falling symbols.

Barometric Pressure, Real Time Clock, and Mega 2560 Woes

Today is Arduino day. First off, I grabbed the new BMP085 module from Sparkfun, and modified the examples to talk to my lcd instead of serial output. It's displaying

"Temperature -2678 Pressure 52029"

which can't be right, so I whipped off a email to Sparkfun tech support for some guidance. Then I grabbed the DS1307 real time clock module from Sparkfun, and again changed the code to display on my lcd (what's with all the serial output code folks? I don't want to have my laptop up just to see the time). Got

0:0:0 0/0/0

which also isn't right. Found a website which claimed their code works with lcd, so I uploaded their sketch. My pin 13 LED started flashing, and now can no longer upload code to my Arduino Duemilanove 328P. All I get is

"avrdude: stk500_recv(): programmer is not responding"

I rebooted my laptop, and no change. Ok, time to pull out the new Arduino Mega 2560. Oh, wait! No, that requires IDE version 0020, which isn't available for linux yet.

I'm going to go watch some tv ......

Update: 20 minutes after I posted this, The folks at Arduino posted version 0021 of the IDE, which includes the linux version. Yeehaw!

Wednesday, September 29, 2010

Arduino - X10 Communications


This library enables you to send and receive X10 commands from an Arduino module. X10 is a synchronous serial protocol that travels over AC power lines, sending a bit every time the AC power crosses zero volts. It's used in home automation. You can find X10 controllers and devices at,, and more.
This library has been tested using the PL513 one-way X10 controller, and the TW523 two-way X10 controller. Both of these are essentially X10 modems, converting the 5V output of the Arduino into AC signals on the zero crossing.
To connect an Arduino to one of these modules, get a phone cable with an RJ-11 connector, and cut one end off. Then wire the pins as follows:


Arduino Temp / Humidity Video

We put together a quick video explaining our Arduino / Temp Humidity monitor to go along with our Instructable. We now have the barometric pressure and real time clock modules to upgrade the main unit, and will be working on that this weekend.

Tuesday, September 28, 2010

The NEW Arduino Mega 2560 arriving shortly!

Hacktronics notified us today that the new Mega 2560 was shipping out to us. We are very excited to try this brand new board and put it through its paces. The extra IO will come in handy as we expand our weather station. Read more about this fantastic new board at

Monday, September 27, 2010

How to build our weather station

I put a instructable up on how to build our weather station. I will be adding / editing the instructable as the project evolves. This is the current version which includes the temperature and humidity functions. Barometric pressure and time date functions will be enabled as soon as the chips arrive this week.

The Arduino Weather Station / Thermostat - More DIY How To Projects

Sunday, September 26, 2010

3.3v regulator for our Arduino I2C projects

We are using the onboard 3.3v output on our Arduino board to run the SHT21 temp/humidity sensor. It's limited to 50 ma, so we are building a 100ma circuit, using the LE33CZ-TR voltage regulator, and two capacitors. We are using a 12v nominal input, but this circuit will handle up to 18v input (for when the house batteries are charging at 14.4 or so, and the occasional 15v equalize).

497-4258-1-ND (LE33CZ-TR 3.3v Regulator) $0.88

BC1148CT-ND (.1 mf 25v ceramic cap) $0.44

445-2866-ND (2.2 mf 25v ceramic cap) $0.26

I will be building a 5v regulator soon as well with the same input requirements, using the LE50CZ-TR 5v regulator, but Digikey did not stock this part at the moment. The inhibit circuit shown does not exist in the 3 leg TO-92 package, only in the surface mount 8 pin SO-8.