[monkeysinacan] wanted to add a fog machine to his Halloween display, but he says that the cheaper consumer-grade models are pretty unruly beasts. He cites short duty cycles and tricky fog control as his two biggest gripes with these sorts of foggers. He decided make the fogging process a little more manageable, and modified his to only generate fog when someone was walking nearby.

One obvious concern with this sort of setup is the warm-up time required to get the device ready to produce fog. If it were to only turn on when someone walked by, [monkeysinacan] would miss his mark each and every time. To ensure that his machine was accurate, he rigged it so that the heat exchanger stayed powered on, triggering the fog juice pump as needed.

To do this, he used an ultrasonic sensor similar to, but cheaper than a Parallax Ping unit. Paired with an Arduino, the sensor triggers the fog machine’s pump for 20 seconds whenever anyone gets within 6 feet of it.

While he hasn’t posted video of the modified fogger at work, it sounds like a solid plan to us.

[Rob] built this hexapod one day when he had some free time after work. Just like the last hexapod we saw, he based the build on the Pololu design which uses three servo motors for surprisingly reliable movement.

The hardware is very straight forward. A Dorkboard serves as the brain. It’s a PCB that is wider on each side by the width of one female pin-header than a standard AVR 28-pin microcontroller. This gives easy access to all of the pins on the Arduino chip while making it small and light. You can see that a four-pack of batteries hangs below the servo motors to provide power.

Protruding above the 6-legger is a PING ultrasonic rangefinder. This adds autonomy to the little robot, which you can see running some obstacle avoidance routines in the video after the break. We’ve asked [Rob] if is able to share his code and will update this post if we hear back from him.

Update: Here’s a link to the sketch, and we’ve updated the picture with one that [Rob] sent to us.

Don’t forget, Prizes and glory await the winner of the Design Challenge. Just 12 days left to get em in.

Just a quick bonus hack: The giant altoids tin battery pack w/voltmeter. [Via Make]