John Donovan
Low-Power Design
When I was a boy I loved flying model airplanes. I’d laboriously build them from balsawood kits; cover them with tissue; and add a noisy .049 gas engine. Then I’d go to the neighborhood schoolyard and get dizzy flying them in endless circles at the end of control cables. Today for under $100 you can buy a Styrofoam plane with a battery-powered engine and wireless remote control – a cheap radio-controlled (RC) aircraft.
I bought one recently and took it to the neighborhood schoolyard where my son and I had a lot of fun with it. The noisy gas engine had been replaced by a small MCU-controlled BLDC motor running off a 7.2 V/1000 mAh NiMH battery. I could easily add a small camera and transmitter and our inexpensive model airplane would suddenly become an unmanned aerial vehicle (UAV) – also known as a drone!
It turns out that a lot of engineering creativity is going into these things. The web site DIYDrones claims to be “the leading community for personal UAVs.” A very active site, it’s sort of a cross between SourceForge and Home Depot. You can download and/or buy just about all the hardware and software you’d ever need to create your own backyard drone.
The tiniest of the lot is the CrazyFlie Nano Quadcopter that can sit in the palm of your hand but zoom around like a crazed hummingbird, controlled from your PC or Android phone. The CrazyFlie is controlled by a 32-bit STMicro MCU and includes a 3-axis MEMS gyro, 3-axis accelerometer, an altimeter, sensors for heading measurement, and a 0 dBm (1 mW) 2.4 GHz transceiver. Weighing in at just 19 gm it can only carry a payload of 10 gm, so it would be hard pressed to carry a camera – though it’s possible – but it can pack an array of LEDs so you can chase the cat around in the dark. If you want to get creative the software is open source, and expansion headers let you trick out the hardware, too. Priced at $179 with radio.
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| CrazyFlie Nano |
If you want the real deal the ArduCopter 3.0 – built around the venerable Arduino platform – claims to be “more than your average quadcopter” (whatever that might be). It’s an open-source multi-rotor UAV. This bad dog includes:
- Automatic takeoff and landing
- Auto-level and auto-altitude control
- ArduPilot, which can automatically pilot the copter to up to 35 waypoints and return it to the launch point (GPS module required, of course)
- A complete Robot Operating System that can enable multi-UAV swarming (hopefully that’s an option you can turn off)
- MissionPlanner software, which lets you click on waypoints on a map, to which the Arducopter will then fly
- Fully scriptable camera controls that can be preset for each waypoint – or you can control them in real time
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| ArduCopter 3.0 |
Since the ArduCopter is a kit, it can take a number of configurations, with lots of options. If you want one ready to fly, the base price is $600 – though it goes up quickly from there.
If fixed wing is your cup of tea – and you don’t care about keeping a camera pointed at one place – there’s the ArduPlane, which won the 2012 Outback Challenge UAV competition. Base price is $550, but the extra goodies can add up.
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| ArduPlane |
Finally, if you already have an RC plane you can buy APM 2.5 autopilot with GPS ($179) – well, and maybe an optional telemetry kit ($75) – and convert your RC airplane into a fully autonomous UAV. But don’t forget the 5.8 GHz video transmitter and receiver ($190). Suddenly my $95 plastic plane costs 5x as much as I first put into it.
Maybe I’m not that interested in seeing what’s in my neighbor’s yard after all.
