The digital scale project has been a measured success, as most maker projects tend to be “in the early revisions”.
On the one hand, the circuit works dandy when it’s up; step on scale, weight gets transmitted, computer processes and saves. I’ve been charting my weight daily for over a month now in this manner.
On the other hand, there are a few… usability concerns. Foremost, because the scale has no way to power down the Arduino, I have to remove the battery to turn things off every morning. This is less than user-friendly. Second, I find myself unimpressed with the transmission range of the XBee. With the computer in direct line of sight and less than 10 feet away, I get nearly 100% transmission. Being able to add some kind of handshaking/feedback so that the user knows that the computer received the transmission would make things better (would allow the computer to be out of sight, for instance).
In all, it works, but it’s a bit of a pain.
While I was building the original circuit, I looked around for a power-saving solution, and I came up with watchdog and sleep. That’s an … OK… solution, but I was really looking for something to kill the power completely.
And then I found this auto powerdown circuit. Very cool! I am so adding this to the build. Great little utility circuit, especially if you have a uC around anyway.
Update: I guess other folks are learning how to make the Arduino go silent, too; I just found an article online about a guy who can make his Arduino run on a AA battery for over 5 years.