This project has been done many times, so I won’t go into much detail. I wanted a general purpose notifier, especially once I built Laundrymon. I figured a box with a high powered RGB LED and an XBee would fit the bill. The enclosure is just a project box with a sheet of cheap copy paper shaped with some wire and hot glue. I added a photoresistor to dim the light in the bedroom at night.

I’m building a couple of these to scatter throughout the house so I always know when the laundry’s done, an email arrives, or whatever else I might want to be notified about.

Important note: I misplaced one of the capacitors when designing the board. It seems to be running well enough with a wire in its place. It’s the one on the right in the lower left corner, above the power connector.

Downloads the source and Eagle files
Buy the PCB from BatchPCB

The ideal approach would be something that I could put next to the washer and dryer that would passively detect whether the machine was running. Laundry machines generally vibrate pretty much, so I decided to try to use an accelerometer to detect vibration. The Wii Nunchuk is a handy accelerometer with an I2C interface with Arduino code available. So I bought an adapter, wrote a basic logging sketch, and taped a Nunchuk to the side of the washer to see what would happen.

Hey, looks like this might actually work!

It turns out that even if you pay the full retail price of $20, the Nunchuk is still pretty much the cheapest accelerometer you can buy once it’s broken out from a tiny surface mount package. I needed two Nunchuks — one for the washer and one for the dryer. Normally, it’s easy to have multiple I2C devices connected together, but the Nunchuk has the slave address hard coded. That’s easily solved with a few transistors.

Time to put it all together. While the Nunchuk adapters are great for prototyping, they don’t really give a solid connection, so I swapped the cable for some network cable I had lying around. I started with a basic breadboard Arduino tutorial, and added an XBee for wireless and the nunchuk circuitry. I used the excellent BatchPCB for fabrication. Even though the final board doesn’t looks much like an Arduino, it’s based on at Atmega168, so I can still use the Arduino IDE to develop the firmware.

Right now, all it does it play a sound on my home theater PC. My next project is to make a bunch of blinkie notifiers to scatter throughout the house.

Download the source and Eagle files
Buy the PCB from BatchPCB

Annoyingly, the factory and universal remote only had a button to toggle through the various inputs. This gets tedious quickly when you have a few video game consoles. I knew that the TV had discrete codes, which would take you directly to a selected input. But I didn’t have a way to program the remote with these codes.

So I wrote an IR transmitter for Arduino. Then I could use the Arduino to program the remote, and have nice discrete component access straight from the remote that I’m already using. My TV is a Samsung, which uses the . It’s a pretty simple protocol consisting of two address bytes and two command bytes, with a 9 ms burst ahead of it. Ones and zeros are encoded as different pauses after a short burst at 38 kHz. My previous IR project was very helpful for debugging timing issues.

Download the code. The only hardware required is an IR LED attached to pin 13.

As a quick-and-dirty solution, I wrote this sketch for the Arduino, using a generic IR remote receiver. When reset, the Arduino starts listening for an IR remote command. It remembers the timing of the pulses, then listens for a similar set of pulses and signals over the serial port. I wrote a few lines of Python to listen to the serial port and do something interesting.

Now I can eject a DVD without messing with any menus. I’ll probably need a more complete solution some day, but for now, I’m set.

Download IRMon

My first guess was a bad solder joint, specifically the wire soldered to the mini-DIN connector. If that went open, the voltage divider would pull the data input to the XBee to ground. That joint wasn’t particularly great to begin with, and got pushed around when finishing assembly and using the board.. Unfortunately, I had covered the mini-DIN solder joints in hot glue in an attempt to prevent physical stress, so I couldn’t just heat up the joint and toss on a bit more solder. I replaced the connector with a spare, but the problem was still there.

That’s when I noticed that the amount of bad data didn’t seem to be change when poking at the board and wires, so it probably wasn’t a physical problem. I measured the voltage on the data input pin, and discovered it was only about 1.6V. That puts it in the undefined area of whether the XBee will consider it high or low. So I found the problem.

Different families of logic devices have different ranges of voltages that it will consider high or low, or output as high or low. Unfortunately, the Roomba doesn’t document it’s thresholds, just that it’s a 5V device. It turns out mine seems to output at about 3.4V, at least under the conditions I tested it.

I clipped off the bottom half of the voltage divider (R4), leaving a 1 kΩ resistor between the Roomba’s output and the XBee’s input, and the noise went away. So it works, but is it safe?

In short, no. But there isn’t enough documentation to design a safe divider. The XBee doesn’t give a maximum safe voltage, but the EM250 that it’s based on says Vcc + 0.3V. I’m supplying 3.3V to the XBee, so that means up to 3.6V. The Roomba doesn’t document it’s maximum output. If I divide enough to keep safe at 5V input, it wouldn’t work at the measured 3.4V.

For now, I’m living dangerously. The remaining resistor (R3) should protect against high current, which tends to be more damaging. If I damage the XBee, I’ll have to design a new board. And then come up with a use for an XBee without a working serial input.

• First semi-practical use of XBee
• First time designing a PCB, using Eagle
• First custom PCB order, from BatchPCB

The board is pretty simple. It has a voltage regulator and a very simple voltage divider to connect between the Roomba’s 5V and the XBee’s 3.3V serial interface. [edit: See my post on the problem with this design] The XBee is more than just a radio, it has a couple of analog/digital converters, and a couple of general purpose I/O pins. I connected the baud select/wake pin on the Roomba to one of the XBee’s outputs, so I can wake up the Roomba remotely.

There’s no microcontroller on the board. The idea is that all processing will be done remotely, and controller via the Roomba’s serial interface over the XBee link.

The software isn’t far enough along to share, but in the meantime, RoombaComm works if you configure the XBees appropriately.

• Download the Eagle and Gerber files
• Buy the board from BatchPCB

When I heard about Libelium’s Arduino Hacking Life contest, I knew it was time for me to finally solve one of my daily annoyances — setting the alarm clock.

Every night, the alarm gets set to a different time. Sometimes there’s an errand in the morning, sometimes an early meeting. On weekends, the alarm usually isn’t needed, unless something’s going on. And then in the morning, I need to set the clock again for my wife’s own set of daily scheduling variables.

Enough! Why should I need to deal with this? Why should I need to stand there pressing buttons time and time again? Why can’t I set my alarm clock with the rest of my schedule — in the calendar? Larmie solves all these problems.

Larmie consists of four components:

1. A regular alarm clock, with an interface cable added
2. An Arduino with a custom shield, for interfacing with the clock
3. A computer, which regularly updates the Arduino with what time to set the alarm to
4. A calendar system. Larmie currently uses Google Calendar

To start, I cracked open my 10+ year old alarm clock. Newer ones might be different, but I’d expect to see essentially the same design in just about every clock. Between the buttons and the LCD is a DIP IC. This looks promising. It’s labeled as LM8560, which a quick Google search tells me is an all-in-one alarm clock. Jackpot.

What I want to do is twiddle the voltage on the LM8560’s input pins, to simulate pressing the buttons on the clock. According to the datasheet, they’re activated at the supply voltage. This is a problem, since the supply voltage is something like 11V, which the Arduino can’t output by itself. To get around this, I used a 7405 hex inverter with open collectors that I had lying around. The hex just means there are 6 inverters (NOT gates) on the chip. The open collector is what’s interesting. When the gate output is logical false, it’s pulled to 0V. When it’s logical true, the pin floats. You can pull it to whatever voltage you need. I pull it to the clock’s high with a resistor, and put in an LED as an indicator. After testing it out a breadboard, I put together the final circuit on some perf board. Here is the schematic.

The Arduino expects to be told the alarm over a serial connection. This can actually be over USB, XBee, Ethernet, or whatever is convenient. I followed the datasheet for how to set and reset the alarm and time. The datasheet doesn’t describe how quickly you can pulse the inputs, but I found that 25 ms and 25 ms off works reliably, and still fast enough to set the time in a few seconds. The biggest challenge in writing the Larmie firmware was avoiding setting off the alarm while setting it. If the current time and alarm time are ever the same, the alarm will continue to go. On top of that, I can’t read the current time out of the clock. Instead, I have the current time sent along with the alarm time. Since there might be a minute or two difference between the clock and the time on the PC, I’ll need to avoid a whole range. That gets complicated around the beginning and end of an hour, so the firmware simply refuses to set the alarm at those times. Since the PC component should be running every few minutes, this doesn’t matter very much.

The last piece is a small Python script that requests event data from Google Calendar, and sends the alarm time to the Arduino. This script should be run periodically, using something like launchd on OS X, cron on Linux, or Scheduled Tasks on Windows. The interface between the PC and the Arduino is very simple, so this component can be swapped out for whatever’s convenient.

Download the source, including circuit diagram, Arduino code, and Python.

Source code for Larmie

Everything should work now.

The API that time around was CoreGraphics, and the theme was Time.

Fuzzy Freddy is an action-packed game of adventure, romance, and hygiene. It is a Universal binary and is best viewed in at least 1280×1024.

I’m pretty happy about how it turned out.

Download Fuzzy Freddy (includes source)

Here’s the description from the readme:

Close is an intense psychological thriller of a game, where the player must avoid getting their personal space invaded by coworkers in a highly detailed workplace environment.

Use your mental and physical abilities to your fullest to defend yourself against these intrusions.

Using Apple’s Core Image technology, Close provides a level of visual quality never before seen in a game of its kind.

Download Close 1.0

Edit: Okay, I’ve been caught. It’s a clone of Daleks. Enjoy the bonus level.