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zlite's blog
Posted by zlite | Jul 22, 2007 @ 02:51 AM | 3,980 Views
In my quest for the perfect pan-tilt gimbal assembly for a small UAV, I've made one out of Lego and some clumsy ones out of aluminum. Most commercial pan-tilt assemblies are made for much larger cameras than the ones we fly, or they're incredibly expensive turrets meant for military and commercial UAVs. But I've hunted around and found three that appear to be within our size, weight and price range. How do they stack up?

The three are (from left to right in the picture below):

* The Lynx B Pan & Tilt kit ($35.93 with servos) link
* The Budget Robotics Pan & Tilt Turret for sensors ($34.95 with servos) link
* The Pandora Pan & Tilt assembly ($29.95 without servos; servos will for you another $20 or so) link

First, some general notes about all three. The most important thing is something you can see from the picture. The first two are designed for standard size servos, which are a bit big for our UAVs. Only the Pandora gimbal is designed for mini and micro servos. It's also the only one specifically designed for the Panasonic KX-131 video camera (shown) that is commonly used in R/C aerial videography, and is the core of the RangeVideo system we use. I haven't shown the other two with the KX-131 mounted (it's a pretty simply matter of drilling some holes or using double sided foam tape), but you can see that it would make them much taller than the Pandora system (they'll stick out almost twice as far).

The other two are intended for...Continue Reading
Posted by zlite | Jul 16, 2007 @ 03:36 AM | 13,075 Views
If you're going to build a UAV, why not start with a cool Predator airframe? Nitro Models makes a really nice (and cheap: $80) one with a 75" wingspane (basically it's got the dimensions of a powered glider). I modded it by replacing the brushed motor with an AXI 2208 brushless and added proper landing gear and an airscoop to cool the motor in the back. (BTW, Nitro sells two Predators. Get this one, not the similar camo version with a slightly smaller wingspan. That one's wings don't come off! I have no idea how you're supposed to transport it, short of a van).

But there's more to this Predator than meets the eye. It's not just a model of an Autonomous Aerial Vehicle--it is a UAV! How can you tell? Look at the second image.

That's a Pentax W30 camera, which is one of the smallest cameras to have proper programmable time-lapse photography setting. Why would I want to strap a camera with a time-lapse function to the bottom of a R/C plane? Because it's not just a R/C plane!

Check out what's under the canopy (third pic), or at least the first layer of it. It shows the installation of a UNAV Picopilot GPS-guided autopilot. This makes the Predator totally autonomous. You can enter up to 20 GPS waypoints, and the Predator will fly to them and then return home afterwards. That, in turn, explains the time-lapse camera. It snaps a 7 megapixel picture every ten seconds while the UAV is following its programmed course. Which means that you can stitch those pictures...Continue Reading
Posted by zlite | Jul 13, 2007 @ 03:37 AM | 3,960 Views
I seem to have gotten the UAV bug pretty badly. In an effort to make drones out of whatever stuff happens to be laying around the house (I dignify this by calling it the "Minimum UAV Project"), I've now got nearly complete UAVs based on Lego Mindstorms NXT, a cellphone, and a BASIC Stamp chip meant for battlebots.

All of them are essentially software projects, since the hardware sides are pretty straightforward. The first of them, based on Lego Mindstorms, also had a fun challenge of squeezing Lego gears and beams, a NXT brick and a bluetooth GPS module into an Electrostar. But the cellphone autopilot (based on a GPS-enabled iPaq phone) was just a matter of strapping the phone to the bottom of the plane and doing all the work of navigation, picture-taking and text messaging commands and imagery in Windows Mobile Visual Basic. Finally the BASIC Stamp autopilot turned out to be a tricky job of squeezing GPS navigation, altitude hold and RX-to-autopilot handoffs in a processor with only 26 bytes of variable memory! But it's working now...

I'm documenting all of this on my own site at This summer all three UAVs (plus a reference UAV based on the off-the-shelf Picopilot system) will fly autonomously, so I should have some test flight videos to share over the next month or two. Unless they just fly off into the sunset, of course, in which case my fascination with UAVs may start to temper a bit!