Global Sources
EE Times-India
Stay in touch with EE Times India
EE Times-India > Embedded

RC helicopter: Ready for takeoff

Posted: 26 Nov 2008     Print Version  Bookmark and Share

Keywords:remote-control  RC helicopter  helicopter rotors  controller 

Even if you're not a child any more agewise, the toy section of many stores still holds some intriguing electronic gems. Here we examine an interesting remote-control (RC) gadget, in the form of Revell's RC helicopter. Measuring over 30 cm long, the device is quite a lot of fun—we put it through some parking lot shenanigans before teardown analysis.

Ready for takeoff: With few electronics, both cost and mass are kept down

The helicopter is powered by a rechargeable Li-Polymer battery pack, which is tucked between the two underside runners and is responsible for controlling all helicopter electromechanics. To receive the 27-MHz controller signal, the helicopter's antenna uses a simple stranded wire, compacted and hidden by spiraling around both runners and snaking over the main helicopter body area. Because an "open" 27-MHz communication band is used between remote and helicopter, electrical length of the antenna is significant. But wire is cheap, as is the labyrinthine implementation of the Chinese manufacturing.

Counter-rotating helicopter rotors in the Revell counter the natural tendency of helicopters to spin from torque reaction in a single main-rotor design. The vertical tail rotor you see on real helicopters is the means by which torque-spin is normally controlled; co-axial (torque-cancelling) designs have been commercially implemented in the real thing, though without much success.

The design is based around three DC motors, the two largest of which drive the two main rotors by way of a set of co-axial shafts, each serving a pair of blades. The outer shaft "sleeve" controls a lower rotor while the inner shaft drives the upper, counter-rotating blades. Pitch and yaw are supported as the control axes, because the blades are at a fixed incline. Steering is accomplished by setting up a differential rate of spin for each of the two rotor blades to control directional torque and thus pointing. A third motor spins a horizontally oriented tail rotor to affect pitch—a nose-up or nose-down orientation—by implementing lift or sink at the helicopter tail.

That sounds pretty fancy but the product must be implemented on the cheap in light of the Rs.5,003.64 ($100) retail price, including the handheld controller. Unlike the conveniently rechargeable helicopter itself, the controller uses a rather mind-boggling (and bank-breaking) eight AA cells. The resulting 12-V rail is perhaps necessary to implement a simple radio with adequate output to cover a useful range.

1 • 2 Next Page Last Page

Comment on "RC helicopter: Ready for takeoff"
*  You can enter [0] more charecters.
*Verify code:


Visit Asia Webinars to learn about the latest in technology and get practical design tips.


Go to top             Connect on Facebook      Follow us on Twitter      Follow us on Orkut

Back to Top